Transition metals ligand bending

In the transition metal complexes which have been structurally characterized, the C02 ligands are bent with internal O—C—O angles varying from 101° to 136°.17 Thus, the vibrational bands for coordinated C02 do not resemble those of the linear molecule (vasym 2349, vsym 1388 or 1285 (one due to Fermi resonance both IR inactive) and 6 667 cm-1), but may be more closely related to metal-bound C02- or to free radical anion. IR spectral bands for the radical anion are calculated at 1,677 cm-1, 1,405 (stretching) cm-1, and 607 (bending) cm-1. 

Binding of a paramagnetic, redox-inactive [Cr(CN)6]3- anion to specific sites of a blue copper protein, amicyanin, has been used in NMR-spectroscopic studies of the protein structure in solutions.285Ab initio calculations of the ligand-field spectra of [Cr(CN)6]3 have been performed and the results compared with those for cyano complexes of the other first-row transition metals.286 The role of Cr—C—N bending vibrations in the phosphorescence spectra... 

In the parallel investigation of systems where metal-ligand charge-transfer (MLCT) occurs, studies into transition metal complexes of the redox-active quinone ligand have unravelled crossover behaviour that accompanies electron transfer. This reversible process, known as valence tautomerism, has been observed with bistability in the solid state. ° Exotic photomechanical behaviours, such as the bending of crystals of ID chain materials with IR irradiation,have been attributed to the unique structural consequences of electron transfer within the solid. 

Martin RL, Taylor D (1976) Bending of linear nitric oxide ligands in four-coordinate transition metal complexes. Crystal and molecular structure of dinitrosyldithioacetylaceto-natocobalt(—I), Co(NO)2. Inorg Chem 15 2970-2976... 

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