EPR SPECTROSCOPIC AND THEORETICAL-STUDY CHROMIUM(I) CARBONYL PHOSPHINE AND PHOSPHONITE COMPLEXES

isotropic and frozen-solution EPR spectra are reported for several Cr( I) carbonyl complexes of the type cis-[Cr(CO)(4)L-2](+), mer- and fac- [Cr(CO)(3)L-3](+), and trans-[Cr(CO)(2)L-4](+), where L is a monodenta te (or L-2 a bidentate) phosphine or phosphonite ligand. Extended Huck el molecular orbital theory calculations were performed for cis-and tr ans-[Cr(CO)(4)L-2], mer- and fac-[Cr(CO)(3)L-3], and cis-and trans-[Cr (CO)(2)L-4] (L = PH3, P(OH)(3)). The EPR results are discussed in ligh t of the electronic structure predictions, which also provide some ins ights on the oxidation potentials and the isomerization reaction energ etics of these complexes. Isotropic P-31 hyperfine couplings can be un derstood in terms of spin densities in the Cr 3d, P 3s, and P 3p orbit als.