He-I and He-II photoelectron studies of bonding in metal silylamido-complexes, M[N(SiMe3)2]n(n= 1,2, or 3)

Abstract

Gas-phase He-I and He-II photoelectron spectra have been obtained for the following bis(trimethylsilyl)amido-metal complexes : M[N(SiMe₃)₂] where M = Li or Na; M[N(SiMe₃)₂]₂ where M = Mg or Co; M[N(SiMe₃)₂]₃ where M = Al, Cr, Ce, Pr, Nd, Eu, Yb, or U. Nitrogen lone-pair and metal–nitrogen π-bonding ionization energies show a constant trend throughout the series, increasing with the charge and decreasing with the size of the metal ion. A d band similar to that of Cr[N(CHMe₂)₂]₃ is detected for Cr[N(SiMe₃)₂]₃, and a very weak 4f band is the first ionization band in the spectrum of Ce[N(SiMe₃)₂]₃. The 5f band of U[N(SiMe₃)₂]₃, has a full width at half maximum of 1 eV, part of which is due to unresolved spin–orbit coupling.