Role of the trigonal t2e2-nen single-ion configuration in d3d3 metal-metal .sigma.-bonded dimers

Abstract

The theory of the trigonal t e single-ion and (t e)(t e) pair configurations is presented in which account is taken of the single-ion electron repulsion, cubic and trigonal ligand Fields, Zeeman splitting, and the M-M π interaction of the pair. Application of the theory to the electronic spectra of M0X (X = Cl, Br) species offers a viable explanation for the broad spin-allowed bands observed above 16000 cmin terms of singly excited pair states involving the trigonal t→ e orbital transition. Furthermore, the anomalously low orbital g values reported previously for the lower lying pair multiplets in the chloro complexcan be explained by extensive mixing of the single-ion tand e orbitals by the M-Mπ interaction and are consistent with the value of J≈ 7000 cmobtained from a recent analysis of the double excitation region of the electronic spectrum of CsMoCl .