An experimental and theoretical investigation of the electronic structure of Pd and Pt bis(carbene) complexes

Photoelectron spectra and density functional calculations are reported for M(CN2R2C2H2)2 (M = Pd, Pt); bonding occurs predominantly through ς donation from the carbene lone pairs into a metal (dz2 + s) hybrid; the corresponding (dz2 – s) is destabilised with respect to the other metal orbitals; there is little evidence for π bonding and the carbene π orbitals are essentially unperturbed on complexation.