Photoelectron studies of metal carbonyls. Part 4.1—Mono-substituted complexes of chromium and tungsten carbonyls

Abstract

The photoelectron spectra of complexes of the general formula [M(CO)₅L], where M = Cr or W, and L = amine, phosphine or isonitrile, have been examined using He I radiation and that of [Cr(CO)₅ NMe₃] using He II radiation. A clear splitting of the predominantly metal d-levels into e and b₂ components is resolved in the case of the amine derivatives, and an asymmetric band envelope is found for the phosphine and isonitrile complexes. The assignment of these bands is facilitated by the presence of spin-orbit splitting of the e level in the tungsten complexes. The reasons for the e–b₂ splitting are discussed with aid of ab initio SCF–MO calculations of [Cr(CO)₅NH₃] and [Cr(CO)₅PH₃] which do not suggest that a simple explanation in terms of the π-acceptor character of the substituent is valid. The M—L σ-bonding level is clearly separated from the d-orbital region, and exhibits anomalously high relative intensity in the HeI spectrum.