Publisher Summary This review is concerned with the neglected class of inorganic compounds, which contain ions of the same element in two different formal states of oxidation. Although the number of references cited in our review show that many individual examples of this class have been studied, yet they have very rarely been treated as a class, and there has never before, to our knowledge, been a systematic attempt to classify their properties in terms of their electronic and molecular structures. In the past, systems containing an element in two different states of oxidation have gone by various names, the terms “mixed valence,” nonintegral valence,” “mixed oxidation,” “oscillating valency,” and “controlled valency” being used interchangeably. Actually, none of these is completely accurate or all-embracing, but in our hope to avoid the introduction of yet another definition, we have somewhat arbitrarily adopted the phrase “mixed valence” for the description of these systems. The concept of resonance among various valence bond structures is one of the cornerstones of modern organic chemistry.

Mixed Valence Chemistry-A Survey and Classification

Publisher Summary This chapter discusses crystal structures of metal–peptide complexes. Most of the crystal-structure analyses of metal–amino acid and metal–peptide complexes have been carried out on the assumption that such complexes act as models for the metal-binding sites on proteins. Crystal-structure analyses show that the geometrical features of metal complexes of amino acids, peptides and imidazole are related in systematic ways to the chemical structure, which the complexes have in the crystalline state. Moreover, the transfer of geometrical information from crystal-structure analyses to species that exist in solution depends on the assumption that the complexes found in crystals are present also in the solutions from which the crystals grow. This chapter illustrates that, the existence of cis-trans isomers coordination isomers, optical isomers, and dimeric species in the crystalline complexes emphasizes the variety of species, which must be considered when equations are written to represent metal–peptide equilibria in solution.

Crystal structures of metal-peptide complexes.

New platinum complexes with anti-tumour activity

(1) The origins of absorption bands of co-ordination compounds have been discussed.(2) The first band is attributed to electron transitions in the unsaturated transition shell of the central ion. The band, therefore, appears only when the central ion is of a transition element.(3) The shift of the first band by substitution of ligands may be explained by postulating that the electron transitions are more or less depressed by the negative field of the ligand, which may conveniently be represented by P, the energy of approach of the ligand, i.e., the work done by the ligand if it were to approach from infinity to the seat of coordination. The ascending order of P i.e., the sequence of hypsochromic effect, is theoreticallyNH_3, H_2O, F^-, Cl^-, Br^-, I^-.The empirically obtained order of hypsochromic effect on the first band is & NO_2^-, NH_3, ONO^-, H_2O, NCS^-, NO_3^-, SO_4^-,& OH^-, C_2O_4^-, CO_3^-, S_2O_3^-, Cl^-, CrO_4^-, Br^-. All the experimental rules so far obtained of the shifts of the first bands...

Absorption Spectra of Co-ordination Compounds. I

Ernest Gordon Cox

Papers

178. The stereochemistry of quadricovalent atoms : copper and silver

211. Isomerides of quadricovalent palladium and platinum

99. The planar configuration for quadricovalent nickel, palladium, and platinum

27. The planar configuration of quadricovalent compounds of bivalent copper and nickel

260. The crystalline structure of tetramminoplatinous chloride