The photoelectron spectrum of MoWCl4(PMe3)4: the position of the valence σ-ionization in quadruply bonded compounds

Abstract

The photoelectron spectrum of MoWCl₄(PMe₃)₄ shows three resolved peaks in the valence region which are assigned to the δ(b_2g), π(e_u), and σ(a_1g) molecular orbitals which form the metal–metal quadruple bond; the linear trend in the ionisation potentials in the three MM′Cl₄(PMe₃)₄(M or M′= Mo and/or W) compounds strongly suggests that the π and σ orbitals overlap in Mo₂Cl₄(PMe₃)₄ and other Mo₂ quadruply bonded compounds.