Facets of Coordination Chemistry

The following sections are included:

• FOREWORD

• PREFACE

• CONTENTS

Alfred Werne, propounded the famous coordination theory 100 years ago and on July 22, 1992 during the 29th International Conference on Coordination Chemistry held at Lausanne, Switzerland (July 19-24) which one of the authors (BVA) had the opportunity to attend, recalled Werner's contributions and a stock was taken of the work done in this field in various parts of the globe. The other days of the conference attended by nearly a gathering of 1000 from all over the world were devoted to several areas of current interest in presentations by participants and this led to interesting discussions. Besides contributed papers, several plenary lectures by experts were delivered, which have been published in a book form ‘Perspectives in Coordination Chemistry’, Ed. Williams, Floriani and Merbach (Verlag Helvetica Chimica Acta, Basel, 1992)…

The coordination chemistry of the environment represents a useful approach to the understanding of chemical properties of fresh water and sea water systems. The coordination chemistry of these systems differs in three respects: most complexes do not involve transition metals, most complexes are labile, and the ligands are simpler (water, hydroxide, chloride, fluoride, carbonate, sulfate), though interesting exceptions are noted. Principles of coordination chemistry are applied to some contemporary environmental problems, including: the natures of metallic species in the oceans and in fresh water, the red tide problem (sudden appearance of microorganisms in the marine environment that are responsible for massive fish kills and paralytic shellfish poisoning), proliferation of fresh water aquatic vegetations, and carbonate geochemistry.

The following sections are included:

• Introduction

• Cobalt Complexes
  • Discovery of Monomeric Dioxygen Adducts
  • Bonding, Spectra and Solution
  • Dioxygen Affinities
  • Coboglobins

• Iron complexes
  • Requirements for Synthetic O₂-carriers
  • Steric
  • Low Temperature
  • Attachment to Rigid Surfaces

• Manganese Complexes

• Acknowledgements

• References

The synthesis of a novel series of bimetallic alkoxides during the last three decades has been followed by a successful synthesis during the past five years of a series of intriguingly stable heterometal alkoxides containing three or four different metal atoms in the same molecular species.

The increasing importance of the use of mixtures of two and more than two metal alkoxides as precursors for the preparation of a wide variety of novel ceramic materials by the SOLUTION - SOL-GEL (S-S-G) process has led to the possibility of molecularly designing a heterometal alkoxide corresponding to the composition of a targetted final ceramic. This has been made feasible by the extraordinary stability of the framework of heterometal alkoxides, which appears to remain intact during the initial hydrolysis reactions involved in the S-S-G process.

The characterization (by sophisticated physico-chemical techniques including X-ray crystal structure eludication in a few cases) of these heterometal alkoxides appears to have added a new class of heterometal coordination systems which appear to be uniquely stable without the presence of metal-metal bonds or auxiliary ligands like Co, etc., generally required for stabilizing polymetallic systems known so far.

The effects of solvents on the rates and activation parameters of the solvolysis of halogenoamminecobalt(III) and related substrates have been highlighted. Both electrostatic and nonelectrostatic medium effects are important. The reactivity patterns are sensitive to the nature of the substrates and that of the cosolvents. Molecular recognition through hydrophobic/hydrophilic interactions between substrates and cosolvent systems appear to control the thermodynamics of solvation and hence the kinetic pattern. Solvent structural effects on the activation energetics are also evident.

The model recently introduced for fitting various properties of ion exchangers is extended to binary mixtures in general. Assuming the effective coordination number in the solution to be z the model leads to a binomial expansion to the power z. The terms in the expansion correspond to one kind of quintuplet etc. By least squares methods the coefficients to each term in the expansion are obtained.

The model is applied to enthalpies and excess volumes of mixing.

The bond-length variation rules and the so called spillover-effect and the pile-up-effect are discussed in terms of inter- and intramolecular charge transfer, i.e. in terms of donor- and acceptor interactions. Furthermore a rule is formulated for the variation of bond angles in both the donor- and the acceptor system. Experimental and theoretical results for various reactions like the complex formation of boranes with amines, spin-state transitions in solution of iron-coordination compounds, the structural variability of trimethyltinchloride and vanadyl-acetylacetonate in various solutions are discussed along these lines. The mechanism of the formation of cis-and trans- isomer species of solvatochromic and thermochromic (i.e. chromotropic) Ni(II)-complexes, as detected by means of the isokinetic relationship (IKR) is described. The application of solvatochromic compounds for the quantitative evaluation of the donor- and the acceptor properties of solutions is described and donor numbers various amines and for anions in solution are derived.

The use of NMR spectroscopy of molecules oriented in liquid crystalline media to study weak molecular complexes is reported. After briefly describing the basic methodology, applications to hydrogen bonded interactions and π charge transfer complexes are illustrated. Changes in molecular order and/or structure as a result of complexation are usually employed for such a purpose.

A number of methods have been developed for the study of electrode reactions, and recently there has been a upsurge in the application of electroanalytical methods to the study of redox changes occurring in compounds of different types. Amongst these, cyclic voltammetry (cv) is most widely being used as the technique of choice, because it provides significant information about the different steps in a redox reaction which can be easily interpreted. The application of cyclic potential scan on a stationary electrode makes it possible to investigate the products of the electrode reaction and also detect the reaction intermediates. Both, relatively slow and fairly rapid reactions can be studied by this technique, because the time scale for the scan can be varied over an extremely wide range…

The following sections are included:

• Organic Polymers

• Preparation of chelating polymers

• Characterization of chelating polymers and their metal complexes

• Applications of chelating polymers

• Use of chelating polymers in inorganic analysis

• Use of chelating resins in organic analysis

• Conclusion

• Acknowledgement

• References

The following sections are included:

• Applications of Sephadex gel and its ion-exchanger columns

• Applications of Toyopearl ion-exchanger or Toyopearl derivative columns

• Applications of clay mineral columns

• Conformation analysis of ion-pairs

• References

The following sections are included:

• Introduction

• SECTION 1 Effect of the Geometrical Isomerism of Transition Metal Complexes on their R_F values obtained by PC
  • Octahedral complexes
  • Square planar complexes

• Effect of the absolute configuration of cobalt(III) complexes on their R_F values obtained by PC

• Effect of the chelate ring size on the R_F values of cobalt(III) complexes obtained by PC

• Effect of an increase in the number of carbon atoms in the ligand branched chain on the R_F values of cobalt(III) complexes obtained by PC

• References

• SECTION 2 Effect of the Geometrical Isomerism of Transition Metal Complexes on their R_F Values obtained by TLC
  • Octahedral complexes
  • Square planar complexes

• Effect of the absolute configuration of cobalt(III) complexes on their R_F values obtained by TLC

• Effect of the chelate ring size on the R_F values of cobalt(III) complexes obtained by TLC

• Effect of the number of side chain carbon atoms in a ligand on R_F values of transition metal complexes obtained by TLC

• Chelate Ligand Substituent effect on R_F values of Transition Metal Complexes obtained by TLC

• Effect of the Central Ion on R_F values of Transition Metal Complexes obtained by TLC

• References

• LIST OF ABBREVIATIONS

This paper discusses designs of various polyether types, including acyclic polyalkoxylates, crown ethers, and bis-crown ethers as sensors for ion-selective electrodes. Examples are drawn from researches in the author's laboratories on sensors for lithium and other alkali metal cations, barium, uranyl and guanidinium, 4.4'-dipyridyl, paraquat and diquat organic cations.

Copper is one of the essential trace elements in the biological systems and it is third in abundance after zinc and iron. The normal quantity of copper in a human adult of 70 kg is 80-120 mg. If the amount of copper in the biological system is in excess, it can have toxic effects…

The following sections are included:

• Introduction

• Mechanism of Urinary Stone Formation and its Architecture

• Factors which favour the formation of a stone

• Remedial Measures
  • Chemolysis
  • Magnesium Oxide and Magnesium Hydroxide
  • Ethylenediaminetetracetic Acid (EDTA)
  • Thiazide (Bendrofluazide) 5-10 mg/day
  • Allopurinol (Xyloric) 150-200 mg/day
  • Orthophosphates
  • Sodium Cellulose Phosphate
  • Pyruvate Salts
  • Pyrophosphate and Methylene Blue
  • Citrate (Hydroxy acids)

• Recent Advances

• Nutrition

• Diet

• Folk Medicine
  • U.S.S.R.
  • Middle-East (Iran)
  • India

• References

The following sections are included:

• SUBJECT INDEX