Chromium compounds, electronic structure

Electronic Structure of Cr11 Compounds. In an octahedral environment two electron distributions, t2gee and t24, are possible. The magnetic data available show that in general chromium(n) compounds are of the high-spin type. The Curie-Weiss law is usually obeyed and the moments are 4.95 B.M., i.e., close to the spin-only value. Aside from the alkanoates and the benzoate, there is a red form of the formate which is nearly diamagnetic, but a blue paramagnetic formate exists also the structures are probably different from that of the acetate (see above). The [Cr(CN)6]4- ion has a moment of only 3.2 B.M. and is thus a low-spin complex. 

Three studies of titanium(m) compounds have been described. Full details have now been given of the five-co-ordinate bis(trimethylamino)titanium tribromide structure which has trigonal-bipyramidal geometry. The titanium co-ordination polyhedron has, within the limits of experimental error, i>s symmetry, in contrast to that of the analogous chromium compound, which has a distorted geometry. The lack of distortion in the titanium(in) structure is ascribed to the location of the single unpaired electron in a non-deforming e orbital. 

The electronic structure 1 was rationalized with the aid of density functional theory calculations (B3LYP/6-31G ). The HOMO and HOMO-1 are 5 bonds, which have the weakest bonding interaction between the chromium ions. The HOMO-2 corresponds to the Cr o-bond, while the two %-bonding interactions (HOMO-3 and HOMO-4) have the lowest energy. Therefore, this compound can be thought to have a o Jt 5 electronic configuration. 

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