Conducting inorganic complexes

Fig. 1. Electrolytic cell used for the electrochemical syntheses of highly conducting inorganic complexes.

Braterman, P. S., P. B. P. Phipps, and R. J. P. Williams Charge-Transfer Phenomena In Some Inorganic Complexes. I. Electronic Conduction In Some Complex Cyanides. J. Chem. Soc. 6164 (1965). 

The following is a case history of the one-dimensional inorganic complex, K o.5lr(CO)2Cl2, which exhibits high conductivity at room temperature. This complex exhibits a variety of unusual properties which indicate a columnar structure and a partially oxidized character in spite of the original proposals for its structure. This material serves as an instructive example to point out several features which make the complex worthy of detailed study. To date, the detailed study of its electrical, magnetic, and optical properties has not been reported. 

Recently Krogmann et al postulated a cation-deflcient, partially oxidized formulation for this material, K o.5lr(CO)2Cl2, and a columnar structure in the solid (16). This one-dimensional structure is consistent with the observed diamagnetism, stoichiometry, IR spectra, dc conductivity, and visual appearance of the complexes. Preliminary powder x-ray data support this formulation with a short 2.86 A Ir-Ir distance. This information sets a basis for the interpretation of detailed optical, electrical, and magnetic measurements that will help in further understanding of the chemistry and physics of one-dimensional inorganic complexes. 

Several 1-D inorganic complexes are comprised of alternating mixed valent complexes with long equivalent metal-metal spacings. Complexes of this type have been observed for Au -Au h Pd -Pd, and Pt -Pt (4, 6). The complexes of [M(amine)2X3] (X = halide) stoichiometry have halide atoms bridging the and atoms, but they are clearly associated with the tetravalent metal (6). The resultant properties are best described in terms of the sum of the individual molecules and are placed in Class II by Robin and Day (21, 24). Low conductivity has been observed for compounds of this type. 

A new material may or may not be nonstoichiometric. Most complexes are stoichiometric. If an inorganic complex exhibits high anisotropic conductivity, the complex may be nonstoichiometric. 

Part II surveys the inorganic materials which exhibit or potentially exhibit a columnar structure. Emphasis is placed on square planar third-row transition metal complexes which exhibit the properties of anisotropic electrical conductivity and the first-row transition metal complexes which exhibit anisotropic cooperative magnetic behavior. The measured chemical and physical properties of the known one-dimensional inorganic complexes are summarized and a number of potentially one-dimensional materials are surveyed. The known one-dimensional magnetic systems are then presented. An extensive reference list including citations through the beginning of 1975 is included to make it easy for the reader to go further into areas of his particular interest. 

The chemical and physical properties of inorganic complexes which exhibit a columnar structure are discussed below. Section II. A discusses highly conducting one-dimensional inorganic materials which may be described in terms of a partially occupied electron energy band. Section II.B describes those complexes which exhibit a columnar structure and generally low conductivity. Several less well characterized materials which may exhibit columnar structure are introduced in Section II. C. Section II. D selectively surveys inorganic polymers, with emphasis on poly(sulfurnitride). 

Partial oxidation is the only method successful so far in achieving onedimensional highly conducting systems, but partial oxidation is not sufficient for high conductivity. All partially oxidized inorganic complexes characterized to date are nonstoichiometric. The determination of these nonstoichiometric ratios is the most direct way to determine the degree of partial oxidation. However, the errors associated with routine elemental analyses may be too large to allow the accurate determination of the constancy of the nonstoichiometric composition. 

In Section 8, the material on solubility constants has been doubled to 550 entries. Sections on proton transfer reactions, including some at various temperatures, formation constants of metal complexes with organic and inorganic ligands, buffer solutions of all types, reference electrodes, indicators, and electrode potentials are retained with some revisions. The material on conductances has been revised and expanded, particularly in the table on limiting equivalent ionic conductances. 

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