Charge distribution chromium complexes

C. Milsmann, A. Levina, H. H. Harris, G. J. Foran, P. Turner, and P. A. Lay, Charge distribution in chromium and vanadium catecholato complexes X-ray absorption spectroscopic and computational studies, Inorg. Chem., 45 (2006) 4743 -754. 

Consequently, these charge effects are reflected in the carbonyl stretching frequencies (87, 88). It has recently been found from studies of the far infrared spectra that the metal-carbon stretching frequencies also support the theory (89). These charge-distribution effects are supported further by the observed dipole moments (90-92). Thus the dipole moments of the chromium tricarbonyl complexes of hexamethylbenzene, benzene, and methylbenzoate lie in the order 6.22, 4.92, and 4.47 /x, respectively. The relationship of charge effects to chemical reactivity is described below. 

Bautista and Hard (B8) made a comparative study of the extractability of. several of the first-transition metals from thiocyanate solutions using methyl isobutyl ketone as the organic solvent. The transition metals readily extracted were scandium (III), iron (III), and cobalt (II) while chromium (II) and manganese (II) were not. The principal extractable species were found to be the neutral scandium and iron trithiocyanate complexes, while the extractable cobalt complex was the negatively charged tetrathiocyanate radial Co(SCN)4 . The distribution ratio for scandium, iron, and cobalt decreased with increase in metal ion concentrar tion but increased with increasing ionic strength of the solutions. 

Chromium- 0) and -(i). An rxtended CNDO/2 method has been used to investigate the energy level distribution and electronic structure of Cr(PF3), as well as other PF3 complexes. The results were compared with experimental data. The metal—phosphorus bonds show large a(P M) and jc(M -> P) charge transfers but small total charge transfers (M - P) which induce on the metal a small positive charge. ... 

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