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Indian Journal of Chemistry

Sect. A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical

 

 

 

VOLUME 42A

NUMBER 9

SEPTEMBER  2003

 

CONTENTS

Papers

2163

Formation of complex three-dimensional inorganic open-framework structures from secondary building units

 

 

 

C N R Rao

 

 

 

2175

The bioinorganic chemistry of copper

 

 

 

 

 

R N Mukherjee

 

Some results on synthetic modeling of a selected number of copper proteins/enzymes are described.

 

2185

Synthesis, crystal structure and nuclease activity of bis(dipyridoquinoxaline)copper(I) perchlorate

 

 

Pattubala A N Reddy, Bidyut K Santra, Munirathinam Nethaji &
Akhil R Chakravarty*

 

 

 

2191

 

Electronic interactions in meso ferrocenyl porphyrin and its metal derivatives

 

 

 

Sundararaman Venkatraman, Viswanathan Prabhuraja, Rajneesh Mishra, Rajeev Kumar,Tavarekere K Chandrashekar*, Weijie Teng & Karin Ruhlandt Senge

 

 

 

2198

Free-base, copper(II) and zinc(II) derivatives of an azomethine bridged ‘porphyrin–pyrene’ dyad: Synthesis, spectroscopy and photochemistry

 

P Prashanth Kumar & Bhaskar G Maiya*

 

 

M= 2H, Cu(II) or Zn (II)

 

2205

Iron (III) porphyrin catalyzed epoxidation of 1,4-diphenyl butadiene

 

 

Parvesh Wadhwani, Kaliappan Kamaraj & Debkumar Bandyopadhyay*

 

 


 

 

 

2210

Synthesis, structure, spectra and redox behaviour of copper(II) complexes of certain bis(phenolate) ligands: Phenoxyl radical complexes of copper(II) as models for galactose oxidase

 

 

 

 

 

 

 

 

 

 

 

Mathrubootham Vaidyanathan , Mallayan Palaniandavar*  & R Srinivasa Gopalan

 

Copper(II) complexes of certain tetradentate tripodal               and linear bis(phenolate) ligands have been synthesized as models for GOase enzyme. The influence of the phenolate substituents on the PhO- ® Cu(II) LMCT transition and the Cu(II)-phenolate/Cu(II)-phenoxyl radical redox potentials are discussed in the light of those of GOase enzyme.

 

     

 

2223

 

Redox reaction between [Bu4N]2[MoVIO2(mnt)2] and thiophenol in relevance to the autoreduction in the crystallization process of oxidized form of sulfite oxidase

 

Pradeep K Chaudhury, Kowliki  Nagarajan, Anil Kumar, Rabindranath Maiti,
Samar K Das & Sabyasachi Sarkar*

 

 


 

 

 

2228

 

Novel ABO3 oxides related to perovskite and YAlO3 structure types in the La-B-V-O (B = Ni, Cu) systems

 

 

 


Z Serpil Gönen, Tapas Kumar Mandal,
J Gopalakrishnan*, Bryan W Eichhorn & Richard L Greene

 

             

 

 

 

 

 

 

            color             B=Ni                            B= Cu

 

2235

 

Organic-inorganic hybrid materials of the copper molybdate family. Syntheses and structures of [Cu(tpa)Mo2O7], [Cu(Me2bpy)Mo2O7] and
[Cu(t-Bu2bpy) Mo4O13] (tpa = tri-2-pyridylamine, Me2bpy = 5,5
¢-dimethyl-2,2¢-bipyridine, t-Bu2bpy = 4,4¢-di-tert-butyl-2,2'-bipyridine)

 

 

 

 

 

Randy S Rarig, Lindsey Bewley,
Eric Burkholder & Jon Zubieta*

 

 

 

Organic-inorganic  materials of the copper–molybdate family have been prepared under hydrothermal conditions. The use of sterically hindered organic subunits results in a series of low dimensional (I-D) structures , characterized by different molybdate substructures.

 

2244

Hydrothermal synthesis and characterization of new one-dimensional tellurates, A2[Te3O8(OH)4] (A = Cs, Rb, K, Na)

 

 

 

M P Minimol & K Vidyasagar*

 

 

 

 

2250

 

Two new 3D architectures of Cu(II): Syntheses, crystal structures and low temperature magnetic studies

 

 

 

Sudipta Dalai, Partha Sarathi Mukherjee, Joan Ribas, Carmen Diaz,
Ennio Zangrando &
Nirmalendu Ray Chaudhuri*

 

 


 

 

 

 

2256

1D Manganese(III) and iron(III) coordination polymers containing Schiff-base ligands and dicyanamide

 

 

 

David J Price, Stuart R Batten, Boujemaa Moubaraki & Keith S Murray*

 

 

 

2267

 

Reactions of 1,3,5-benzenetricarboxylic acid with Zn(II) ion in the presence of added amines: Isolation and structure determination of zinc coordination polymers with tetrahedral and octahedral zinc centres

 

 

 

 

 

Divya Krishnamurthy &
Ramaswamy Murugavel*

 

 

 

The change of the auxiliary ligand (C) in the reaction between 1,3,5-benezenetricarboxylic acid (B) and divalent zinc (A) results in the isolation three different types of extended solids, with the compositions ABC, AB or BC.

 


 

 

 

 

2277

Studies on bioctahedral dirhenium(II) complex cations that contain nitrile ligands including the structural characterization of [Re2Cl3(μ-dppm)2 (CO)(CNXyl)(NCC5H4N)]O3SCF3

 

 

 

 

 

David A Kort, N Dastagiri Reddy,
Phillip E Fanwick & Richard A Walton*

 

 

 

2283

 

Synthesis, characterization, electrochemistry and photophysical studies of tetranuclear ruthenium(II) complexes with two new spacers containing four 1,10-phenanthroline units as donor

 

Parimal Paul*, Beena Tyagi  &
P Natarajan*

 

 

Two novel tetranuclear ruthenium(II) complexes have been synthesised by the reaction of two new spacers containing four 1,10-phenanthroline units as donor sets and cis-[Ru(bpy)2Cl2] as building block. Electrochemical and spectroscopic studies show that there is weak or no intercomponent electronic communication between metal centers. Both the complexes exhibit strong luminescence at room temperature; their emission life times have been determined by laser flash photolysis experiments.

 

 

2290

Synthesis & formation of dinuclear mixed-valent complexes of ruthenium & osmium bridged by
2-(2-pyrimidyl)benzimidazolate

 

 

 

 

Masa-aki Haga*, Masahide Ishizuya, Tomokazu Kanesugi, Tomona Yutaka, Daisuke Sakiyama, Joerg Fees & Wolfgang Kaim

 

 

 

 

2300

 

Supramolecular encapsulation of anions in a copper(I) complex

 

 

 

 

D Saravanabharathi & A G Samuelson*

 

 

 

2307

Effect of supramolecular aggregation on coordination in cobalt (II) complexes of
 2-imidazolidone

 

Larry R Falvello*, Eva M  Miqueleiz, & Milagros Tomás

 

 

 

2316

Binding of nitrate anion in a supramolecularly constructed macrocycle

 

 

 

 

 

Pritam Mukhopadhyay, R J Butcher &
Parimal K Bharadwaj*

 

A mono-derivatized cryptand upon acidification with dilute nitric acid, affords a supramolecularly constructed macrocycle which accepts two nitrate  anions in the cavity.

 

 

 

2320

Regioselective fusion of aromatic di-amines to coordinated 2-(phenylazo)pyridine. An approach to the synthesis of new ligands with large denticity

 

 

 

 

 

Kunal K Kamar, Partha Majumdar,
Alfonso Castiñeiras & Sreebrata Goswami*

 


 

 

2327

New azoiminato complexes of bivalent platinum: Syntheses, characterisation and structure

 

 

 

Nilkamal Maiti & Surajit Chattopadhyay*

 

 

2332

 

Dicationic dihydrogen complexes of iron with almost no Fe–h2-H2 back-bonding

 

 

 

 

 

 

 

H V Nanishankar, Munirathinam Nethaji &
Balaji R Jagirdar*

 

 

 

2339

Synthesis and characterization of
2-dimethylaminoethylthiolate complexes of palladium(II) and platinum(II)

 

 

 

 

 

 

 

 

 

 

 

Sandip Dey, Vimal K Jain*, Axel Knoedler & Wolfgang Kaim*

 

Reaction of Na2PdCl4 with Me2NCH2CH2SH.HCl in methanol affords a trimeric complex [PdCl (SCH2CH2NMe2)]3. Treatment of [M2Cl2(m-Cl)2(PR3)2] (M = Pd or Pt) with Me2NCH2CH2SH.HCl in the presence of NaHCO3 yields complexes of the type [MCl(SCH2CH2NMe2)(PR3)]n (n = 1 or 2).

 

 

 

2344

Synthesis, characterization and structural studies of metal complexes based on dmit, dmt and tbs ligands. Crystal structure of [PPN][Au(dmit)2].CH3CN

 

 

 

 

 

 

 

 

 

 

Kochurani, K Kandasamy, H B Singh*, & Babu Varghese

 

 

 

 

2352

Cobalt(II) and cobalt(III) complexes with
N-(aroyl)-N
¢-(picolinylidene)hydrazines. Spin-crossover in the cobalt(II) complexes

 

 

 

 

Subramanya Gupta Sreerama, Dharavath Shyamraj, Satyanarayan Pal & Samudranil Pal*

 

 

 

Synthesis, structure and physical properties of mononuclear cobalt(II)/(III) complexes containing N4O2 coordination spheres assembled via pyridine-imine-amide donor tridentate ligands are described.  Thermally induced spin-crossover phenomenon is observed in the cobalt(II) complexes.

 

 

2359

Magnetic and spectroscopic studies of ferricenium tetrabromoferrate(III),
[Fe(C5H5) 2].+[FeBr4].-, a soft ferromagnet and its
iodo analogue

 

 

 

 

 

 

 

 

 

 

K Padmakumara, T Pradeep, J Ensling,
P Gütlich  & P T Manoharan*

 

 

A soft ferromagnetic material having the molecular formula C10H10Fe2Br4 has been  characterized by magnetic susceptibility, EPR and Mössbauer spectroscopies. The corresponding iodo derivative was found to be antiferromagnetic.

 

 

2371

Synthesis and structure of the macrocycle
[(OCH2CEt2CH2O){P(N-t-Bu)2P}]2

 

 

 

 

 

 

 

 

 

Praveen Kommana, K V P Pavan Kumar & K C Kumara Swamy*

 

 

 

Synthesis and structure of the novel macrocyclic compound [(OCH2CEt2CH2O){P(N-t-Bu)2P}]2 from the reaction of the cyclodiphosphazane with   HOCH2CEt2CH2OH, is reported; the intermediate (OCH2CEt2CH2O){P(N-t-Bu)2PCl}2 has been identified by NMR spectroscopy.

 

 

 

 

 

 

 

2376

Ligand driven assembly of a monoorganooxotin cage from the reactions of organotin precursors with phosphonate ligands

 

 

 

 

 

 

 

Vadapalli Chandrasekhar* & Viswanathan Baskar

 

 

 

 The  reactions of n-BuSn(OH)2Cl with various phosphonate ligands affords the tetranuclear organooxo tin cage [(n-BuSn)2O{O2P(OH)-t-Bu}4]2  in good yields.

 

 

 

 

2382

 

Ab-initio molecular orbital studies on the structural isomers of C3Si2H4

 

 

 

 

 

 

Eluvathingal D Jemmis,* Ramamurthy Saradha, Amaran Saieswari & Elambalassery G Jayasree

 

 

 

 

2392

Effect of cross-linking on catalytic performance of polystyrene supported platinum carbonyl clusters

 

 

 

 

 

 

Himadri Paul, Sumit Bhaduri* &
Goutam Kumar Lahiri*

 

 

The catalysts (1) and (2) have been designed by anchoring Pt15(CO)302- onto the amine functionalized 5% and 8% cross-linked polystyrine resins via anion exchange and the effect of cross-linking on their catalytic performances scrutinized.

    

 

2398

Ruthenium-catalyzed ring-closing metathesis on alkene-tethered Fischer carbene complexes

 

 

Debasis Hazra & Amitabha Sarkar*

 

 

Alkene-terminated tethers have been assembled around a Fischer carbene moiety by C-alkylation of the a-carbon or N-alkylation of amino carbene complexes by a phase-transfer catalyzed procedure.Small or medium-sized, pendant, fused or spirocyclic rings have then been formed.

 

.

 

2406

Osmium mediated decarbonylation of aldehydes and ketones. Synthesis, structure and reactivities of some osmium carbonyl complexes

 

 

 

 

Parna Gupta, Falguni Basuli, Shie-Ming Peng, Gene-Hsiang Lee &
Samaresh Bhattacharya*

 

 

 

 

 

2416

Pd(0), Pt(II) catalyzed carbon-carbon bond formation across tetragonal tin(II) oxide: Synthesis of Ferrocenes with ene-appendage

 

 

 

 

 

Paromita Debroy & Sujit Roy*

 

 

 

2422

Palladium-carbon s-bonded complexes bearing diphosphazane and diphosphazane monosulfide ligands

 

 

 

Swadhin K Mandal,
Setharampattu S Krishnamurthy* & Munirathinam Nethaji

 

 

 

2427

Phenol-amide chelates of iron(III). Kinetics and mechanism of reversible formation of (diaqua) (1,3) bis (2-hydroxybenzamido) propaneiron(III) and its reactions with, thiocyanate, azide, imidazole, sulphur(IV) and ascorbic acid in aqueous medium

 

 

 

Suprava Nayak & Anadi C Dash*

 

 

   (H2L)

Fe(OH2)63+ + H2LFe(HL)(OH2)22+              Fe(L)(OH2)2+

Fe(L)(OH2)2+ + X-  Fe(L)(OH2)X  (or Fe(L)(X))

(for X- = NCS-, N3-,HSO3- (or HAsc-))

 

2439

Selective extraction of alkali metal ions from bittern using picrate anion and crown ethers as ligand: An experimental and theoretical study

 

 

 

Pragati Agnihotri, Bishwajit Ganguly,
Suresh E., Parimal Paul* & Puspito K Ghosh*

 

 

Dibenzo-21-crown-7 (DB21C7) and dibenzo-24-crown-8 (DB24C8) are used for extraction of metal ions (Na+, K+, Mg2+ and Ca2+) from bittern and schoenite byproduct. Ion chromatographic study shows DB21C7 extracts K+ with high selectivity. Two-phase extraction equilibrium constants for Na+ and K+ with both the ligands have been evaluated. All of the experimental data have been rationalized on the basis of molecular mechanics calculations using Monte Carlo search method.

 

 

2447

Some studies on recovery of chromium from chromite ore processing residues

 

 

 

 

 

 

 

K J Sreeram, M K Tiwari & T Ramasami*

 

 

Authors for correspondence are indicated by (*)

 

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2163-2174

 

 

Formation of complex three-dimensional inorganic open-framework structures from secondary building units

C N R Rao

 

Investigations of open-framework zinc phosphates have demonstrated that the formation of the complex 3D architectures may involve a process wherein one-dimensional ladders or chains, and possibly zero-dimensional monomers comprising four-membered rings transform to the higher dimensional structures. The one-dimensional ladder and the 4-membered rings appear to be important building units of these structures. At one stage of the building-up process, spontaneous self-assembly of a low-dimensional structure such as the ladder could occur, followed by the crystallization of a three-dimensional structure. Accordingly, many of the higher dimensional structures retain structural features of the 0D or 1D structure. It is significant that a four-membered ring zinc phosphate has been found recently to spontaneously yield a linear chain phosphate at room temperature, on addition of piperazine, the chain transforming to a sodalite-type 3D structure under mild conditions. The occurrence of a hierarchy of structures from zero- to three-dimensions is found in open-framework metal oxalates as well. Interestingly, the three-dimensional sodalite structure is generated readily by the assembly of metal squarates, possessing the 4-membered ring motif. It is noteworthy that open-framework structures are also formed by oxyanions such as sulphate and selenite.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2175-2184

 

The bioinorganic chemistry of copper

R N Mukherjee

 

Many enzymes and proteins have copper at their active sites, which plays a key role in biology. An important goal of bioinorganic chemistry is the development of small inorganic coordination complexes that reproduce structural, spectroscopic features and functional aspects in a manner similar to their natural counterparts. To provide an overview of the activities in this field, some results on synthetic modelling of a selected number of copper proteins/enzymes are described in this article.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2185-2190

 

Synthesis, crystal structure and nuclease activity of bis(dipyridoquinoxaline)copper(I) perchlorate

 Pattubala A N Reddy, Bidyut K Santra, Munirathinam Nethaji & Akhil R Chakravarty*

 

A copper(I) complex [Cu(dpq)2](ClO4) (1), where dpq is dipyrido-[3,2-d:2¢,3¢-f]-quinoxaline, is prepared and structurally characterized. The complex crystallizes in the orthorhombic space group Pnna with the unit cell parameters a = 7.7797(9) Å, b = 20.185(2) Å, c = 16.593(2) Å, V = 2605.6(5) Å3, Z = 4. The structure was refined to R = 0.0713 for 2595 reflections with 1127 having I > 2s(I) and 192 parameters. The cationic complex has the copper(I) center bonded to two N,N-donor dpq ligands giving a distorted tetrahedral coordination geometry with a Cu-N distance of 2.05 Å. The crystal structure displays extensive p-p stacking interactions involving the planar aromatic rings of dpq. Such an interaction gives rise to the formation of chains and the perchlorate anions are located in-between the chains. The complex is diamagnetic and exhibits a metal to ligand charge transfer band at 442 nm (e, 6000 M-1 cm-1) in MeCN and a perchlorate stretch at 1088 cm-1 in the IR spectrum in KBr phase. It shows a quasi-reversible cyclic voltammetric response at 0.17 V (DEp = 120 mV) at 50 mV s-1 in DMF for the Cu(II)/Cu(I) couple. Complex 1 is a chemical nuclease. It shows efficient nuclease activity on treatment with supercoiled DNA in presence of hydrogen peroxide. The nuclease activity of 1 is found to be better than [Cu(phen)2]+ under similar reaction conditions. Mechanistic studies have shown minor groove binding of the complex and the involvement of hydroxyl radicals in the DNA cleavage reactions.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2191-2197

 

Electronic interactions in meso ferrocenyl porphyrin
and its metal derivatives

Sundararaman Venkatramana, Viswanathan Prabhurajaa, Rajneesh Mishraa, Rajeev Kumara,
Tavarekere K Chandrashekar*a, Weijie Tengb & Karin Ruhlandt Sengeb

 

Synthesis, characterization, spectroscopic and electrochemical studies on meso tetraferrocenyl porphyrin are reported. Substitution of ferrocenyl groups on the meso carbons affect the electronic structure of the porphyrin as well as the ferrocenyl moiety. This is reflected in the shift of electronic absorption band and redox potentials in the ferrocenyl containing porphyrin relative to the porphyrins without ferrocenyl group. Single crystal X-ray structure of freebase reveals an a,b,a,b orientation of the ferrocenyl groups relative to the mean plane of the porphyrin ring. Introduction of metal into the porphyrin ring does not alter the electronic structure of the metal as revealed by EPR spectrum for Cu2+ derivative.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2198-2204

 

Free-base, copper(II) and zinc(II) derivatives of
an azomethine bridged ‘porphyrin–pyrene’ dyad:
Synthesis, spectroscopy and photochemistry

P Prashanth Kumar & Bhaskar G Maiya*

 

Free-base, copper(II) and zinc(II) derivatives of a porphyrin - pyrene conjugate having an azomethine group separating the two photoactive subunits have been synthesized and fully characterized by mass (FAB), IR, UV/visible, 1H NMR and ESR spectroscopies and also by the cyclic- and differential pulse voltammetric methods. An analysis of the data reveals that the spectral and electrochemical properties of the individual chromophoric entities are retained and that there exists no specific p p interaction between the porphyrin and pyrene subunits in these dyads. Excitation of CH2Cl2 solutions of the free-base and zinc(II) derivatives at 550 nm results in no quenching of fluorescence due to the tetrapyrrolic moiety, but that at 290 nm results in a quenching of fluorescence due to the appended pyrene moiety. Excitation spectral data indicates that photons collected by the hydrocarbon subunit are effectively transferred to the porphyrin in both these donor – acceptor systems.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2205-2209

 

Iron (III) porphyrin catalyzed epoxidation of 1,4-diphenyl butadiene

 Parvesh Wadhwani, Kaliappan Kamaraj & Debkumar Bandyopadhyay*

 

The meso-tetrakis (pentafluorophenyl) porphyrinatoiron (III) chloride (F20TPPFeCl) catalyzed mono epoxidation of 1,4-diphenyl butadiene (DPBD) has been achieved by tert-butylhydroperoxide in methanol. This reaction does not proceed in dichloromethane. The most significant observation is that the reaction is inhibited at higher diene concentration. In order to understand the nature of the reactive intermediate in this reaction the same oxidation reaction has been conducted by authentically generated oxo-iron (IV) porphyrin cation radical and by the tert-BuO· radical. Unlike F20TPPFe(III) Cl/t-BuOOH oxidizing system, oxoiron (IV) porphyrin cation radical reacts smoothly with DPBD to produce the monoepoxide in dichloromethane. The yield of the epoxide in the oxidation reaction by oxo-iron (IV) porphyrin cation radical, however, drops drastically when the reaction is conducted in methanol. The results have indicated that in the F20TPPFe (III) Cl catalyzed oxidation of DPBD by tert-BuOOH the oxo-iron (IV) porphyrin cation radical is not the actual reactive intermediate. In the oxidation of DPBD by the tert-BuO· radical the maximum yield of the epoxide has been achieved in neat dichloromethane and the yield goes down in methanol, the trend is just opposite to those observed in the hydroperoxide reactions. The catalyst-hydroperoxide adduct is believed to be the major reactive intermediate in this oxidizing system.

 

 

 

Indian Journal of Chemistry  

Vol. 42A, September 2003, pp. 2210-2222

 

Synthesis, structure, spectra and redox behaviour of copper(II) complexes of certain bis(phenolate) ligands: Phenoxyl radical complexes of copper(II) as models for galactose oxidase

Mathrubootham Vaidyanathan & Mallayan Palaniandavar*

and R Srinivasa Gopalan

 

Copper(II) complexes of a series of tetradentate tripodal and linear ligands containing two substituted phenolates appended to N,N-dimethylethylenediamine and N,N¢-dimethylethylenediamine moieties viz. N,N-dimethyl-N¢,N¢-bis(2-hydroxy-4-nitrobenzyl)ethylenediamine [H2(L1)], N,N-dimethyl-N¢,N¢-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine [H2(L2)], N,N-dimethyl-N¢,N¢-bis(2-hydroxy-3,5-di-tert-butylbenzyl)ethylenediamine [H2(L3)], N,N¢-dimethyl-N,N’-bis(2-hydroxy-4-nitrobenzyl) ethylenediamine [H2(L4)], N,N¢-dimethyl-N,N¢-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine [H2(L5)] and N,N¢-dimethyl-N,N¢-bis(2-hydroxy-3,5-di-tert-butylbenzyl)ethylenediamine [H2(L6)] have been isolated and characterized by electronic absorption and EPR spectroscopy and cyclic and differential pulse voltammetry. Of these complexes, [Cu(L1)]2.2H2O 1, [Cu(L1)(py)] 1a and [Cu(L4)(H2O)].H2O 4 have been structurally characterized by X-ray crystallography. The coordination structure of 1 is dimeric with a trigonal bipyramidal distorted square based pyramidal geometry (TBDSBP) around each Cu(II). In complex 1a also a trigonal bipyramidal distorted square based pyramidal geometry (TBDSBP) around Cu(II) is present. The CuN2O2 basal plane is comprised of two phenolates and a tertiary amine nitrogen of H2(L1) and an exogenous pyridine nitrogen and the dimethyl substituted amine nitrogen of H2(L1) is axially coordinated. In 4, there are two different copper(II) complex molecules in the same unit cell with trigonal bipyramidal distorted square based pyramidal geometry (TBDSBP) around Cu(II). The methyl groups of the ethylenediamine frame are cis to each other in one molecule (A) and are trans to each other in the other molecule (B). The bond lengths and bond angles in the two molecules are different. The ligand field and EPR spectra of all the complexes are consistent with a square-based geometry even in solution. An intense band observed in the range 390-465 nm may originate from Cu(II) ® (phenolate)O-(axial) and/or equatorial(phenolate)O- ® Cu(II) CT transitions. The g|| values lie in the range 2.23-2.29 indicating the presence of CuN2O2 or CuNO3 chromophores. All the complexes show an irreversible CuII/CuI redox process at increased negative E1/2 values, which are consistent with the presence of two coordinated phenolate groups. The oxidation wave(s) occurring in the range 0.06 – 0.89 V (vs Ag/Ag+) demonstrate(s) the formation of phenoxyl radical-copper(II) species. The influence of the phenolate substituents on the PhO-® Cu(II) LMCT transition and the Cu(II)-phenolate/Cu(II)-phenoxyl radical redox potentials are discussed. The stability of the radicals is enhanced with the increase in donor ability of the substituents. The relevance of the notable structural and spectral features of the complexes containing two redox active phenolates bound to copper(II) in a square pyramidal environment, to those of galactose and glyoxal oxidases are highlighted.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2223-2227

 

Redox reaction between [Bu4N]2[MoVIO2(mnt)2] and thiophenol in relevance to the autoreduction in the crystallization process of oxidized form of sulfite oxidase

Pradeep K Chaudhurya, Kowliki Nagarajanb, Anil Kumarb, Rabindranath Maitic, Samar K Dasd & Sabyasachi Sarkarb*

 

[Bu4N]2[MoVIO2(mnt)2] readily reacts with thiophenol leading to its reduction to [Bu4N]2 [MoIVO(mnt)2]. Detailed kinetics of this reaction is presented. The kinetics consists of three consecutive irreversible first order reactions (in the presence of excess of thiophenol) with k1, k2, k3 = 2.82(6) ´ 10-1 s-1, 6.09(5) ´ 10-2 s-1, 1.66(8) ´ 10-3 s-1 and 2.91(4) ´ 10-1 s-1, 6.15(3) ´ 10-2 s-1, 3.41(6) ´ 10-3 s-1 at 298 K in acetonitrile and aqueous-acetonitrile media respectively.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2228-2234

 

 

Novel ABO3 oxides related to perovskite and YAlO3 structure types in the La-B-V-O (B = Ni, Cu) systems

Z Serpil Gönena, Tapas Kumar Mandalb, J Gopalakrishnan*b, Bryan W Eichhorna & Richard L Greenea

 

The synthesis, structure and magnetic properties of mixed-metal oxides of ABO3 composition in the La-B-V-O (B = Ni, Cu) systems are described in the present paper. While the B = Ni oxides adopt GdFeO3-like perovskite structure containing disordered nickel and vanadium at the octahedral B site, La3Cu2VO9 crystallizes in a YAlO3-type structure. A detailed investigation of the superstructure of nominal La3Cu2VO9 by WDS analysis and Rietveld refinement of powder XRD data reveal that the likely composition of the phase is La13Cu9V4O38.5, where the Cu and V atoms are ordered in a Ö13ah (ah = hexagonal a parameter of YAlO3-like subcell) superstructure. Magnetic susceptibility data support the proposed superstructure consisting of triangular Cu3 clusters. At low temperatures, the magnetic moment corresponds to S = 1/2 per Cu3 cluster, while at high temperatures the behavior is Curie-Weiss like, showing S = 1/2 per copper. The present work reveals the contrasting behavior of La-Cu-V-O and La-Ni-V-O systems: while a unique line-phase related to YAlO3 structure is formed around La3Cu2VO9 composition in the copper system, a continuous series of perovskite-GdFeO3 solid solutions, LaNi1-xVxO3 for 0£ x £1/3 seems to be obtained in the nickel system, where the oxidation state of nickel varies from 3+ to 2+.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2235-2243

 

 

Organic-inorganic hybrid materials of the copper molybdate family. Syntheses and structures of [Cu(tpa)Mo2O7], [Cu(Me2bpy)Mo2O7] and [Cu(t-Bu2bpy)Mo4O13] (tpa = tri-2-pyridylamine, Me2bpy = 5,5¢-dimethyl-2,2¢-bipyridine, t-Bu2bpy = 4,4¢-di-tert-butyl-2,2'-bipyridine)

 Randy S. Rarig, Lindsey Bewley, Eric Burkholder & Jon Zubieta*

 

The hydrothermal reactions of CuSO4 • 5H2O and MoO3 in the presence of various sterically hindered polypyridyl ligands have been studied. Under basic conditions, [Cu(tpa)Mo2O7](1) and [Cu(Me2bpy)Mo2O7](2) are formed, while under mildly acidic conditions, [Cu(t-Bu2bpy)Mo4O13](4) is the product. The structures of 1 and 2 are grossly similar in that both are constructed from molybdate chains decorated with secondary metal-ligand coordination cation subunits. In the case of 1, the molybdate chain consists of alternating pairs of edge-sharing octahedra and square pyramids, while for 2, the chain exhibits corner-sharing octahedra with peripheral tetrahedral sites. The profound structural influences of hydrothermal reaction conditions such as pH are dramatically illustrated by the structure of 4 which consists of octamolybdate clusters linked through binuclear {Cu2(t-Bu2bpy)2}4+ sites.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2244-2249

 

Hydrothermal synthesis and characterization of new one-dimensional tellurates, A2[Te3O8(OH)4] (A = Cs, Rb, K, Na)

M P Minimol & KVidyasagar*

 

New isostructural tellurates, A2[Te3O8(OH)4] (A = Cs, Rb, K, Na), have been synthesized under hydrothermal conditions and characterized by X-ray diffraction, thermal and infrared spectroscopic studies. These compounds contain, as determined from single crystal X-ray diffraction study of the potassium compound, linear [Te3O8(OH)4]2- anions and, for charge compensation, A+ ions. Alkali metal ions of these tellurates undergo a partial ion exchange with one another.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2250-2255

 

Two new 3D architectures of Cu(II): Syntheses, crystal structures and low temperature magnetic studies

 Sudipta Dalai, Partha Sarathi Mukherjee, Joan Ribas, Carmen Diaz, Ennio Zangrando§ &
 Nirmalendu Ray Chaudhuri*

 

Two new 3D frameworks based upon copper(II) and 1,2-bis(4-pyridyl)ethane (bpe), [Cu(bpe)(H2O)2] (ClO4)2 (1) and [Cu(bpe)2(dca)2] (2) [dca = dicyanamide anion], have been synthesised and characterised by variable temperature magnetic susceptibility measurements down to 2 K. Complex (1) is a 1D chain with coordinated bpe and water molecules, this chain on interchain H-bonding through counter perchlorate anions and coordinated water produces a 3D architecture. While complex (2) is a a-Po mimetic interlocked 3D architecture produced by the interpenetration of 3D network of Cu(II) with bridging bpe and dca. Low temperature magnetic behaviour down to 2 K reveals the existence of very weak antiferromagnetic interaction in complex 1 whereas complex 2 shows the presence of ferromagnetic interaction through the dca pathway.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2256-2266

 

1D Manganese(III) and iron(III) coordination polymers containing Schiff-base ligands and dicyanamide

David J Price, Stuart R Batten, Boujemaa Moubaraki & Keith S Murray*

 

The 1D coordination polymers, [MIII(Schiff-base)(dca)]n, dca- = dicyanamide, N(CN)2-, MIII = Mn and Fe, Schiff-base= salen2- (N,N¢-ethylenebis(salicylaldiminato)) (1) and (2); sal-o-phen2- (N,N¢-o-phenyleneylenebis (salicylaldiminato)) (3) and (4); (±)-saltch2- (N,N¢-(±)-trans-cyclohexanebis (salicylaldiminato)) (5) and (6), are reported. The complexes consist of octahedral high-spin MIII atoms coordinated in the equatorial plane by the tetra-chelating Schiff-base ligand and coordinated in the axial positions by single m1,5-dicyanamide bridges, forming infinite linear zigzag chains. The chains of complexes 1 to 6 interdigitate in a parallel fashion with adjacent chains, via weak π-stacking. Variable temperature magnetic susceptibility measurements (2-300 K; H = 1 T) have shown that these compounds display very weak antiferromagnetic coupling, and consequently no long-range magnetic order has been observed under these conditions, as expected for isolated 1D chains.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2267-2276

 

Reactions of 1,3,5-benzenetricarboxylic acid with
Zn(II) ion in the presence of added amines: Isolation and
structure determination of zinc coordination polymers with tetrahedral and octahedral zinc centres

Divya Krishnamurthy & Ramaswamy Murugavel*

 

The formation of two metal-organic coordination polymers and an organic supramolecular network based on 1,3,5-benzenetricarboxylic acid (H3BTC) are reported. While [Zn3(BTC)2(DMP)6.2.5H2O] (1) is formed by the addition of zinc acetate and 3,5-dimethylpyrazole (DMP) to H3BTC, the addition of zinc acetate to 4-aminopyridine and H3BTC results in previously reported [Zn3(BTC)2.12H2O] (2). On the other hand, the interaction of H3BTC with ZnSO4 in the presence of piperazine (PIP) leads to the formation of [H2BTC]2[H2PIP] (3) as soluble single crystals in addition to an insoluble zinc-BTC-piperazine complex with unknown composition. The solid-state structures as determined by single crystal X-ray diffraction studies reveal that compounds 1-3 form 3-D polymeric networks with the aid of extensive hydrogen bonding. In 1, the adjacent dimeric units of [(DMP)4Zn2(BTC)2] are bridged by [Zn(DMP)2] units to form a polymeric chain structure. These chains are in turn linked to each other through hydrogen bonding to form a 2-D sheet network. The 2-D sheets are held together by weak p-p interactions to form a 3-D network. Compound 2 is made up of a zig-zag chain of alternating BTC3- ion and Zn(H2O)4 octahedral units. These chains are held together by numerous hydrogen bonding interactions resulting in a porous solid. The supramolecular assembly in 3 can be described as a host-guest complex in which the hydrogen bonded [H2BTC-]n network hosts the piperazinium cations.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2277-2282

 

Studies on bioctahedral dirhenium(II) complex cations that contain nitrile ligands including the structural characterization of
[Re2Cl3(μ-dppm)2(CO)(CNXyl)(NCC5H4N)]O3SCF3

 David A Kort, N Dastagiri Reddy, Phillip E Fanwick & Richard A Walton*

 

The edge-sharing bioctahedral dirhenium(II) complex [Re2Cl3(-dppm)2(CO)2(NCC5H4N)]O3SCF3 (4) (where dppm = Ph2PCH2PPh2) is prepared by the reaction of Re2Cl4(m-dppm)2(CO)2 (1) with 4-cyanopyridine in the presence of TlO3SCF3. This complex (space group P21/n) contains an all-cis arrangement of COt, COb and nitrile-bound 4-cyanopyridine ligands. The Re-Re distance of 2.5789(7) Å is in accord with the retention of a Re=Re bond in 4, as is present in 1. The lability of the acetonitrile ligands in the triply-bonded open bioctahedral dirhenium(II) complexes [Re2X3(m-dppm)2(CO)(CNXyl)-(NCMe)]O3SCF3 (X = Cl (2) or Br (3)) has been investigated by their reactions with the N-heterocycle 3,4-dimethylpyridine (3,4-Me2py) and the tertiary phosphine PEt3. These reactions proceed with retention of stereochemistry (based upon IR and NMR spectroscopy and CV measurements) to afford [Re2X3(m-dppm)2(CO)(CNXyl)(L)]O3SCF3, where X = Cl, L = 3,4-Me2py (5) or PEt3 (6) and X = Br, L = 3,4-Me2py (7) or PEt3 (8).

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2283-2289

 

 
Synthesis, characterization, electrochemistry and photophysical studies of tetranuclear ruthenium(II) complexes with two new spacers containing four 1,10-phenanthroline units as donor

Parimal Paul*a, Beena Tyagi a & P Natarajan*b

 

Two novel tetranucleating spacers (BL1 and BL) incorporating four 1,10-phenanthroline units have been synthesized and characterized. The reaction of these spacers with the building block cis-[Ru(bpy)2Cl2] resulted in the formation of tetranuclear complexes [{Ru(bpy)2}4BL1][PF6]8.2H2O and [{Ru(bpy)2}4BL2][PF6]8.2H2O. Cyclic voltammograms of these complexes show Ru(II)®Ru(III) oxidation at +1.25 V (vs SCE), and a few ligand-based reductions in the region -1.32 to -1.54 V. Both complexes show strong metal-to-ligand charge-transfer (MLCT) band in the visible region (457 and 456 nm). These complexes exhibit strong emission band (3MLCT) at 612 nm. The excited state life-times of both the complexes have been determined by laser flash photolysis experiments. The observed life-times, 252 ns for 1 and 226 ns for 2, and also electrochemical results, however suggest no intercomponent electronic interaction between the metal centers. The transient absorption difference spectra show bleaching of the MLCT band around 450 nm.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2290-2299

 

 

Synthesis & formation of dinuclear mixed-valent complexes of ruthenium & osmium bridged by 2-(2-pyrimidyl)benzimidazolate

 Masa-aki Haga*, Masahide Ishizuya, Tomokazu Kanesugi, Tomona Yutaka, Daisuke Sakiyama,
Joerg Fees & Wolfgang Kaim

 

Mononuclear Ru/Os complexes, [M(bpy)2(Hbimpm)]2+, where Hbimpm = 2-(2-pyrimidyl)benzimidazole, behaves as a monobasic acid to form the conjugate base, [M(bpy)2(bimpm)]2+ where bimpm = 2-(2-pyrimidyl)benzimidazolate. Novel dinuclear Ru/Os complexes bridged by 2-(2-pyrimidyl)benzimidazolate (bimpm) have been prepared from the reaction of M(bpy)2Cl2 with a deprotonated mononulcear complex, [M(bpy)2(bimpm)]+(M = Ru & Os). The MLCT band for the dinuclear Ru complexes, [Ru(bpy)2(L)Ru(bpy)2]n+, is shifted to longer wavelengths in the order of L = bibenzimidazolate (bibzim) > bibzim > bpm. Furthermore, the Kcom value of a mixed-valent complex, calculated from the potential difference between the first & second electron-transfer step, for the Ru complex is larger than that for the Os analogue. The mixed-valent complexes which were generated electrochemically show the intervalence charge transfer band at 1830 nm for Ru & 1300 nm for Os, respectively. The degree of electronic coupling between two metal centers is calculated as 650 cm-1 for Ru & 360 cm-1 for Os, respectively. By comparing the Kcom & Hab values with those of the analogous bridged ligand system such as bpm & bibzim, a synergetic contribution of both electron exchange & hole exchange mechanisms is operative for metal-metal communications in the present bimpm -bridged mixed-valent complexes.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2300-2306

 

Supramolecular encapsulation of anions in a copper(I) complex

 D Saravanabharathi & A G Samuelson*

 

Mixed ligand copper(I) complexes of 1,10-phenanthroline (phen) and 1,2-bis(diphenyl)phosphinoethane (dppe) have been prepared with different counter ions [ClO4-   (1), BF4-  (2), SO42-  (3), NO3-  (4)]. Based on the 1H and 31P NMR spectra of these complexes, it is seen that the solution equilibria of the sulfate complex is different from the rest and involves ligand dissociation. Competition experiments show that the nitrate ion is preferred by the cation in solution. Complex 4 has 1H NMR features that are different from those observed in complexes 1 and 2. A Cambridge Structural Database study has been taken up to show the uniqueness of phenanthroline in interacting with anions, especially nitrate ions through a preferential (phen)C2-O(nitrate) interaction.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2307-2315

 

 

Effect of supramolecular aggregation on coordination in cobalt (II) complexes of 2-imidazolidone

Larry R Falvello*, Eva M. Miqueleiz, & Milagros Tomás

 

The polyfunctional ligand 2-imidazolidone, HimiO, C3H6N2O, reacts rapidly with cobalt chloride hexahydrate at ambient temperature to produce the deep blue product [Co(HimiO)6]­[CoCl4], 2, which can be kept in solution or isolated as stable crystals. A solution of 2 reacts under slightly more forcing conditions with replacement of two HimiO ligands of the cation by water to give the pale pink compound [Co(HimiO)4­(H2O)2]­Cl2·2HimiO, 3, which is isolated only in crystalline form. Upon dissolution in acetone, compound 3 reverts to 2. Crystals of 3 display full use of the hydrogen bonding capabilities of the functional groups, both donors and acceptors, and are comprised of unbounded columnar aggregates held together into bundles by hydrogen bonding with interstitial, unligated HimiO molecules. The aqua ligand plays a key hydrogen-bonding role in the formation of both the columns and the bundles. It is concluded that compound 2 is the favored product in solution and that the formation of stable aggregates drives the crystallization of 3, which is favored in the solid state.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2316-2319

 

 

Binding of nitrate anion in a supramolecularly constructed macrocycle

Pritam Mukhopadhyaya, R J Butcherb & Parimal K Bharadwaja*

 

A laterally nonsymmetric cryptand incorporating three secondary amino nitrogens in the three bridges, have been selectively mono-derivatized with 2,4-dinitrobenzene. The product upon acidification with nitric acid, forms a macrocyclic cavity through hydrogen bonding interactions. This macrocyclic cavity accepts two nitrate anions which has been characterized by X-ray crystallography.

 

 

 

Indian Journal of Chemistry

 Vol. 42A, September 2003, pp. 2320-2326

 

Regioselective fusion of aromatic di-amines to coordinated
2-(phenylazo)pyridine. An approach to the synthesis of new ligands with large denticity

Kunal K Kamara, Partha Majumdara, Alfonso Castiñeirasb & Sreebrata Goswami*,a

 

Metal mediated oxidative fusion reaction of aromatic di-amines to coordinated 2-(phenylazo)pyridine (pap) ligand in the cationic cobalt complex, [Co(pap)3]2+ affords green complexes of general formula [Co(L)2](ClO4) [HL = 2-[(N-aryldiamino)phenylazo]pyridine]. In this reaction one of the two amine functions of the di-amine reagent is fused regioselectively to ortho-carbon of the pendant phenyl ring of coordinated pap to yield a bischelating tridentate ligand while the second amine function remains a pendant and does not take part in the fusion reaction. The crystal structure of one of the representative cobalt complexes, [Co(L2)2](ClO4) is reported. The structure analysis reveals the presence of two anionic ligands, each of which acts as an N,N,N-tridentate donor. Physicochemical properties of the cobalt complexes are reported. The ligands HL2 - HL4 are isolated from the corresponding cobalt complexes by their decomposition. These free ligands showed resolved 1H NMR spectra. The resonance due to -NH and -NH2 in these appeared near 10.5 δ and 4.5 δ, respectively. The ligand HL4 was reacted with salicylaldehyde, which underwent Schiff-base condensation to result an extended ligand H2L5 in a high yield. The 1H NMR spectrum of H2L5 showed the presence of a -CH resonance at 10.6 δ and the -OH resonance at 13.3 δ. FAB mass and 1H NMR spectra of the newly synthesized organic ligands indeed confirm their formulations.

 

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2327-2331

 

 

New azoiminato complexes of bivalent platinum: Syntheses, characterisation and structure

Nilkamal Maiti & Surajit Chattopadhyay*

 

New azoiminato chelates of bivalent platinum, (HL1)2Pt and (HL2)2Pt, have been synthesized by the reaction of potassium tetrachloroplatinate with 2-(phenylazo)aniline (H2L1) and 2-(p-tolylazo)aniline (H2L2) respectively. The (HL1)2Pt crystallises in a space group P21/n. The bond parameters are in accordance with the formation of monoanionic azoiminato ligand. As a result of delocalisation in the ligand backbone, the phenyl ring adjacent to the chelate ring is distorted with four long and two short bonds. The UV-vis spectra of the complexes show intense charge transfer transitions at ~750 nm. IR and 1HNMR spectral data are consistent with amino proton dissociation from the ligand precursor. The cyclic voltammogram of the complexes exhibit two oxidative responses at potentials ~ 0.5 V and ~ 1.2 V vs SCE in dichloromethane-acetonitrile mixed solvent.

 

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2332-2338

 

 

Dicationic dihydrogen complexes of iron with
almost no Fe–h2-H2 back-bonding

H V Nanishankar, Munirathinam Nethaji & Balaji R Jagirdar*

 

Transition metal hydride complexes of the type trans-[(dppe)2Fe(H)(RCN)][BF4] (dppe = Ph2PCH2CH2PPh2; R = CH3, CH3CH2, CH3CH2CH2, CH2=CH, C6H5, p-CH3C6H4CH2) have been prepared by substitution of the h2-H2 ligand in trans-[(dppe)2Fe(H)(h2-H2)][BF4] with the corresponding nitriles. Protonation of these hydride complexes using HBF4·Et2O gives the dicationic dihydrogen complexes trans-[(dppe)2Fe(h2-H2)(RCN)][BF4]2. The intact nature of the H-H bond in these derivatives has been established by the observation of substantial H-D coupling constants for the h2-HD isotopomers and the short spin lattice relaxation times (T1) for the h2-HD ligand. The H2 ligand in these complexes is not substantially elongated indicating reduced or almost no Fe–H2 back-bonding. The bound H2 ligand is quite labile, upon its loss, one of the BF4- counterions binds with the metal to afford trans-[(dppe)2Fe(BF4)(RCN)][BF4] derivative. Reactivity behaviour of the dihydrogen complexes toward Lewis bases such as acetonitrile, triethylamine, and piperidine has been studied. The X-ray structure of trans-[(dppe)2Fe(H)(CH3CH2CH2CN)][BF4] has been determined.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2339-2343

 

 

Synthesis and characterization of
2-dimethylaminoethylthiolate
complexes of palladium(II) and platinum(II)

Sandip Deya, Vimal K. Jain*a, Axel Knoedlerb & Wolfgang Kaim*b

 

Reaction of Na2PdCl4 with Me2NCH2CH2SH.HCl in methanol affords a trimeric complex [PdCl(SCH2CH2NMe2)]3. Treatment of [M2Cl2(m-Cl)2(PR3)2] (M = Pd or Pt) with Me2NCH2CH2SH.HCl in the presence of NaHCO3 yields complexes of the type [MCl(SCH2CH2NMe2)(PR3)]n (n = 1 or 2). These complexes have been isolated as monomeric species containing chelating thiolate ligands. In some cases, with more basic phosphines, binuclear complexes (n = 2) containing bridging thiolate ligands are also formed. All complexes have been characterized by elemental analysis and NMR spectroscopy. The structure of [PdCl(SCH2CH2NMe2)(PPh3)] (2c) has been established by X-ray crystallography.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp.2344-2351

 

 

Synthesis, characterization and structural studies of metal complexes based on dmit, dmt and tbs ligands. Crystal structure of [PPN][Au(dmit)2].CH3CN

Kochurania, K. Kandasamy,a H B Singh*,a, & Babu Vargheseb

 

Dichalcogenene complexes of the formula [cation]n[M(dmit)2]n-, [cation]n[M(dmt)2]n- and [cation]n[M(tbs)2]n- [M = Ni, Cu, Pd, Pt; Au, n = 0-2; dmit = 4,5-dimercapto-1,3-dithiole-2-thione, dmt = 4,5-dimercapto-1,2-dithiole-3-thione and tbs = thiobenezeneselenolate, cation = trimethyltelluronium, (CH3)3Te+, bis(triphenylphosphine)iminium, PPN+, tetrabutylammonium, Bu4N+, and trimethylammonium, Me3NH+] have been prepared. The spectroscopic and electrochemical behaviour have been studied and compared with the related complexes. Oxidation reactions of these complexes with iodine afforded partially oxidized derivatives which exhibit compressed electrical conductivites of > 10-6 S cm-1 at room temperature. The [PPN][Au(dmit)2] complex has been structurally characterized by X-ray crystallography and its structure is compared with the structure of previously reported complexes [(CH3)3Te][Au(dmit)2] and [PPN][Ni(dmit)2].

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2352-2358

 

 

Cobalt(II) and cobalt(III) complexes with N-(aroyl)-N¢-(picolinylidene)hydrazines. Spin-crossover in the
cobalt(II) complexes

 Subramanya Gupta Sreerama, Dharavath Shyamraj, Satyanarayan Pal & Samudranil Pal*

 

Complexes of cobalt(II) and cobalt(III) with tridentate N-(aroyl)-N¢-(picolinylidene)-hydrazines (HL, H stands for the dissociable amide proton) are described. The Schiff bases (HL) have been obtained by condensation of 2-pyridine-carboxaldehyde with benzhydrazide or 4-substituted benzhydrazides. The reactions of Co(O2CCH3)2·4H2O and HL at room temperature under aerobic condition afford the complexes with general formulae [CoIIL2] (-Cl and -NO2 as substituents) and [CoIIIL2]+ (-H, -CH3, -OCH3 and -N(CH3)2 as substituents). The cationic complexes have been isolated as PF6- salts. Analytical, spectroscopic, magnetic and electrochemical techniques have been used for the characterization of these complexes. X-ray structure of [Co(pamh)2]PF6 has been determined. In each complex, the metal centre is in N4O2 coordination sphere constituted by the meridionally spanning pyridine-N, imine-N and deprotonated amide-O donor ligands. Infrared spectra are consistent with the enolate form of the amide functionalities in both ligands. Cobalt(III) complexes, [CoL2]PF6, are diamagnetic and NMR active. In acetonitrile solutions the complexes behave as 1:1 electrolyte. Electronic spectra of the complexes display charge transfer bands in the range 453-221 nm. All the complexes are redox active and display the Co(III)-Co(II) couple in the potential range -0.23 to +0.09 V (vs. Ag/AgCl). The trend in these potential values reflects the effect of the electronic nature of the substituents on the aroyl moiety of the ligands. Cobalt(II) complexes, [CoL2], are paramagnetic and electrically nonconducting in solutions. Variable temperature magnetic susceptibility measurements and EPR spectra reveal S = 3/2 « S = 1/2 spin-crossover in both cobalt(II) complexes.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2359-2370

 

 

Magnetic and spectroscopic studies of ferricenium tetrabromoferrate(III), [Fe(C5H5) 2].+[FeBr4].-, a soft ferromagnet and its iodo analogue

K Padmakumara, T Pradeepa, J Ensling b, P Gütlich b & P T Manoharan*a†

 

Detailed studies of the properties of ferricenium tetrabromoferrate (III) using electron paramagnetic resonance (EPR) and Mössbauer spectroscopy reveal that this material undergoes a magnetic transition at 13.2 K. The origin of this transition has been traced to the near neighbor ferrimagnetic coupling as evidenced by a broadening and the subsequent disappearance of an EPR line due to the 6A1 ground state of FeBr4- and an appearance of the Zeeman split Mössbauer spectrum, the latter in concurrence with earlier reports. Infrared spectrum shows the emergence of new bands around the magnetic ordering temperature. Detailed magnetization measurements as a function of temperature and field clearly indicate long range ferromagnetic ordering at a temperature below 4 K. This is corroborated by Mössbauer results with the appearance of another transition and a six line pattern due to the ferricenium cation at 2.9 K. The mechanism for ferromagnetic coupling is discussed. The change in EPR line-width and the appearance of two new EPR lines below 20 K give additional evidence to the other experimental observations. The EPR, Mössbauer and IR studies suggest that no such ordering exists in the analogous C10H10Fe2I4, probably due to a structural transition at low temperature hindering magnetic ordering.

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2371-2375

 

 

Synthesis and structure of the macrocycle
[(OCH2CEt2CH2O){P(N-t-Bu)2P}]2

 Praveen Kommana, K V P Pavan Kumar & K C Kumara Swamy*

 

The compound [(OCH2CEt2CH2O){P(N-t-Bu)2P}]2 (7) has been synthesized by the reaction of the cyclodiphosphazane [ClPN-t-Bu]2 (1) with an equimolar quantity of 2,2-diethyl-1,3-propanediol. An X-ray structure determination confirms that it is a 16-membered macrocycle. This mode of reaction is compared with those of 1 with various other difunctional amines/alcohols where only monomeric (in cyclodiphosphazane units) compounds are isolated. Reaction of 1 with half mole equivalents of the diols HOCH2CR2CH2OH [R = H, Me, Et] afforded products formulated as (OCH2CR2CH2O){P(N-t-Bu)2PCl}2. Attempts to incorporate lithium ion into 7 and the related methyl compound [(OCH2CMe2CH2O){P(N-t-Bu)2P}]2 (4) have not been successful.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2376-2381

 

Ligand driven assembly of a monoorganooxotin cage from the reactions of organotin precursors with phosphonate ligands

 Vadapalli Chandrasekhar* & Viswanathan Baskar

 

The reaction of n-BuSn(OH)2Cl with t-BuP(O)(OH)2 in a 1:2 ratio in refluxing toluene or stirring in acetonitrile at room temperature forms the monoorganooxotin cage, [(n-BuSn)2O{O2P(OH)-t-Bu}4]2 1 in good yields. The reaction conditions have been varied to optimize the yield of the oxo cluster. An intermediate leading to the formation of 1 has been identified by 31P NMR spectroscopy. Compound 1 can be used as a single-source precursor for the formation of SnP2O7 by a low temperature decomposition process at 750ºC.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2382-2391

 

 

Ab-initio molecular orbital studies on
the structural isomers of C3Si2H4

Eluvathingal D Jemmis,* Ramamurthy Saradha, Amaran Saieswari & Elambalassery G Jayasree

 

The exploration of the potential energy surface of C3Si2H4, which is derived from the well-known pentagonal pyramidal B5H9 structure by isolobal and isoelectronic replacements, shows that there are large numbers of minimum energy structures with the relative energies ranging from 0 to 102 kcal/mol. The global minimum is the unconventional C2v bridged isomer. The PES is characterized by the isomers having (i) pyramidal geometry, (ii) conventional five membered ring systems, (iii) multiple rings shared across their edges and (iv) tetrahedrane structures with the ring strain released through bridging. The low energy isomers are found to be those with (i) divalent silicons, (ii) 3c-2e bonds and delocalization, (iv) sharing through Si-Si linkage between the rings and (v) two silicon atoms meta to each other in the ring.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2392-2397

 

Effect of cross-linking on catalytic performance of polystyrene supported platinum carbonyl clusters

Himadri Paul2, Sumit Bhaduri1* & Goutam Kumar Lahiri2*

 

Commercial chlormethylated divinylbenzene cross-linked polystyrene resins (5.5% and 8%) have been functionalized by the reaction with triethylamine. The Chini cluster [Pt15(CO)30]2- has  been anchored onto the resultant materials by anion exchange. The degrees of functonalization in terms of chloromethyl and benzyltriethyl ammonium functionalities are found to be very high and high (>85% and >60%) respectively for both the polymers. The total platinum content of the 8% cross-linked polystyrene is a little (~ 13%) more than that of 5.5% cross-linked polymer.  The catalytic activities of the resultant materials after mild thermal activation have been studied for the hydrogenation of a variety of unsaturated compounds. The substrates studied are: cyclohexanone, acetophenone, methyl pyruvate, ethyl acetoacetate and nitrobenzene. For most of the substrates the activity of the 5.5% cross-linked material is found to be a little more than that of the 8.8% cross-linked material. This is despite the fact that the latter has more platinum both in the bulk and on the surface as measured by atomic absorption and EDAX (SEM) techniques respectively. After functionalization with cinchonine and [Pt15(CO)30]2-, both the polymers have been tested as possible asymmetric catalysts for the hydrogenation of methyl pyruvate. No enantioselection is observed and a tentative explanation is offered for the lack of enantioselection.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2398-2405

 

Ruthenium-catalyzed ring-closing metathesis on
alkene-tethered Fischer carbene complexes

Debasis Hazra & Amitabha Sarkara*

 

Alkene-terminated tethers have been assembled around a Fischer carbene moiety by C-alkylation of the a-carbon or N-alkylation of amino carbene complexes by a phase-transfer catalyzed procedure developed in this laboratory. Small or medium-sized, pendant, fused or spirocyclic rings have then been formed by ring-closing metathesis involving such substrates in good to excellent yields. By engaging one of the allyl tethers of a diallylamino group as a ligand for the metal center, it is possible to dictate the direction of cyclization by metathesis.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2406-2415

 

 

Osmium mediated decarbonylation of aldehydes and
ketones. Synthesis, structure and
reactivities of some osmium carbonyl complexes

 Parna Gupta, Falguni Basuli, Shie-Ming Penga, Gene-Hsiang Leea & Samaresh Bhattacharya*

 

Reaction of [Os(PPh3)3Br2] with salicylaldehyde or 2-hydroxyacetophenone or 2-hydroxynaphthaldehyde in the presence of a base results in the decarbonylation of these phenolic ligands affording an osmium carbonyl complex, viz. [Os(PPh3)2(CO)2Br2]. The same [Os(PPh3)2(CO)2Br2] complex has also been obtained from the reaction of [Os(PPh3)3Br2] with benzaldehyde, acetophenone and 1-naphthaldehyde in the absence of any base. Reaction of [Os(PPh3)3Br2] with formaldehyde in the presence of a base affords another carbonyl complex, viz. [Os(PPh3)2(CO)2(HCOO)2]. Structure of both the carbonyl complexes has been determined by X-ray crystallography. Reaction of the carbonyl complexes has been carried out with three bidentate ligands, viz. tetrachlorocatechol (H2Cl4Cat), quinolin-8-ol (Hq) and 2,2¢-bipyridine (bpy), which results in the formation of [Os(PPh3)2(CO)2(Cl4Cat)], [Os(PPh3)2(CO)(q)(H)] and [Os(PPh3)2(CO)(bpy)(H)]+ complexes respectively. Structure of [Os(PPh3)2(CO)2(Cl4Cat)] has also been determined by X-ray crystallography. All the complexes are diamagnetic and show intense charge-transfer transitions in the visible and/or ultraviolet region. Cyclic voltammetry of all the complexes in dichloromethane solution shows an osmium(II)-osmium(III) oxidation within 0.56 – 1.15 V vs SCE. The [Os(PPh3)2(CO)(q)(H)] complex also shows an osmium(III)-osmium(IV) oxidation at 1.15 V vs SCE and in the [Os(PPh3)2(CO)(bpy)(H)]+ complex, a reduction of the coordinated 2,2¢-bipyridine ligand is observed at -1.21 V vs SCE.

 

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2416-2421

 

Pd(0), Pt(II) catalyzed carbon-carbon bond formation
across tetragonal tin(II) oxide:
Synthesis of Ferrocenes with ene-appendage

Paromita Debroy & Sujit Roy*

 

Alkenylferrocenes, FcCHCHCHCH2 have been synthesized from formylferrocene and allyl halides using b-SnO and Pd(0) or Pt(II) as co-catalyst in organic aqueous medium. Monoallylated products have been isolated by similar reaction with 1,1¢-bis-formylferrocene. These serve as potential precursors for multinuclear ferrocenophanes with extended conjugated ene-spacer.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2422-2426

 

 

Palladium-carbon s-bonded complexes bearing diphosphazane and diphosphazane monosulfide ligands

 Swadhin K Mandal, Setharampattu S Krishnamurthy* & Munirathinam Nethaji

 

The reactions of the diphosphazanes and diphosphazane monosulfides, Ph2P(E)N(R)PPh2 [E = lone pair, R = CHMe2 (1); E = lone pair, R = (S)-*CHMePh (2); E = S, R = CHMe2 (3); E = S, R = (S)-*CHMePh (4)] with [PdMeCl(COD)] yield the neutral chelate complexes of the type [PdMe{k2-Ph2P(E)N(R)PPh2}Cl] (5, 6, 8 and 9). The reactions of 1-3 with chlorobridged cyclometallated palladium azobenzene dimers, [Pd{(C6H3-R’-4)-N=N-(C6H4-R’-4)(m-Cl)]2 (R’ = H or OC6H13) in the presence of NH4PF6 yield cationic cyclopalladated complexes, [{k2-(C6H3-R¢-4)-N=N-(C6H4-R’-4)}Pd{k2-Ph2P(E)N(R)PPh2}](PF6) (10-15). The molecular structure of [Pd{k2-(C6H3-OC6H13-4)-N=N-(C6H4-OC6H13-4)}{k2-Ph2P(S)N(CHMe2)PPh2}](PF6) (15) has been determined by X-ray diffraction; the palladium bound carbon atom occupies the trans position with respect to the sulphur atom of the chelated diphosphazane monosulphide ligand

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2427-2438

 

 

Phenol-amide chelates of iron(III). Kinetics and
mechanism of reversible formation of (diaqua) (1,3)bis(2-hydroxybenzamido)propane iron(III) and its reactions with, thiocyanate, azide, imidazole, sulphur(IV) and
ascorbic acid in aqueous medium

 Suprava Nayak & Anadi C Dash*

 

(1,3) bis (2-hydroxybenzamido)propane (H2L) forms mononuclear iron(III) complex, Fe(HL)(OH2)22+. The kinetics and mechanism of its formation has been investigated at 25.0 ≤ t/°C ≤ 40.0 (I = 0.3 mol dm-3, 10% (v/v) MeOH + H2O). For the reaction, Fe(OH2)5(OH)2+ + H2L.   Fe(HL)(OH2)22+, k2 (25°C) = (2.14 ± 0.15)´103 dm3 mol-1 s-1, ΔH = 39.7 ± 1.3 kJ mol-1, ΔS =-48 ± 4 J K-1 mol-1; k -2 (25°C) = 0.168 ± 0.0014 s-1, ΔH = 76.0 ± 1.5 kJ mol-1, ΔS =-4 ± 5 J K-1 mol-1 where k2 and k -2 denote the forward and reverse rate constants respectively. Fe(HL) (OH2)22+ is a moderate acid (pK = 2.25 ± 0.05, 25.0°C, I = 0.5 mol dm-3, 20% (v/v) MeOH + H2O). ΔpK (HL--Fe(HL)2+) = 8 is in conformity with the fact that both the phenolic groups are coordinated to iron(III). The metal ion promoted ionisation of the amide function also points to the N-coordination of this tetradentate ligand in Fe(HL)2+/FeL+. The high value of the stability constant of FeL+ (ca log Kstab ≈ 18), which is further enhanced by the amide deprotonation, is favourable for this ligand to be an efficient iron(III) sequestering agent. Fe(L) (OH2) 2+ undergoes facile aqua ligand substitution forming Fe(L)(X)(OH2) (n-1)- (Xn- = N3-, NCS-, imidazole, SO32-); with ascorbate anion (HAsc-) replacement of both H2O occurs leading to Fe(L)(HAsc)/Fe(L)(Asc)- in which HAsc-/Asc2- is chelated (ΔpK(HAsc--Fe(L)(HAsc)) = 6). No significant labilising action of the coordinated amide (even after N-H deprotonation) and phenoxide/phenol functions is evident. Fe(L)(SO3)-, Fe(L)(HAsc)/Fe(L)(Asc)- undergo facile internal redox despite the stabilising action of the multidentate ligand.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2439-2446

 

 

Selective extraction of alkali metal ions from
bittern using picrate anion and crown ethers as ligand:
An experimental and theoretical study

Pragati Agnihotri, Bishwajit Ganguly, Suresh E., Parimal Paul* & Puspito K. Ghosh*

 

Dibenzo-21-crown-7 (DB21C7) and dibenzo-24-crown-8 (DB24C8) have been used to extract the metal ions (Na+, K+, Mg2+ and Ca2+) present in bittern, schoenite and in an artificial solution containing equimolar amount of the above mentioned metal ions. Ion chromatographic study of the organic extract shows that DB21C7 extracts potassium with high selectivity, whereas DB24C8 extracts comparable amount of potassium and sodium. The extraction equilibrium constants (Ke) for potassium and sodium with both the ligands have been evaluated spectrophotometrically by two-phase (water-dichloromethane) extraction process. For DB21C7, Ke value for potassium is 4.5´104 M-2, which is 6.3´102 time higher than that of sodium, whereas DB24C8 shows Ke values 3.3´104 and 2.4´104 M-2 for potassium and sodium, respectively. Molecular mechanics calculations have been performed to examine the selectivity of the cations. In the gas phase calculations, DB21C7 and DB24C8 are found to be selective towards the sodium ion. However, K+ is preferred by DB21C7 in the aqueous solution, which is in qualitative agreement with our experimental results.

 

 

 

Indian Journal of Chemistry

Vol. 42A, September 2003, pp. 2447-2454

 

Some studies on recovery of chromium from
chromite ore processing residues

K J Sreerama, M K Tiwarib & T Ramasamia

 

This work reports a methodology for near complete mobilization and recovery of chromium from chromite ore processing residues. It has been found that it is possible to mobilize chromium from the residues. Various factors which influence the extent of extraction of chromium from COPR have now been reported. An extraction using sodium peroxide enables leaching of more than 95% of chromium in COPR. The method is selective to the leaching of chromium as demonstrated by EDXRF measurements. Leaching of chromium from COPR using peroxides leads also to significant reduction in particle size. The reaction between residue and oxidant has been found to be biphasic. By combining oxidative and chelative methods, a near complete recovery of chromium and iron from COPR has been possible.