The He@) photoelectron spectra of ferrocene, 1,l'-dimethylferrocene, 1 ,l'-dichloroferrocene, ruthenocene, 1,l'-dimethylruthenocene, 1,l'-dimethylosmocene, bis(?r-cyclopentadienyl)magnesium, bis(r-methylcyclopentadienyl)magnesium, and methylcyclopentadiene are reported and assigned using largely empirical arguments. The details of the spectra are discussed using a simple molecular orbital model and compared with the expectations of ligand field theory.

He I photoelectron spectra are reported for the metallocene species ( C5H&V, (C,H,),Cr, (C5H&Mn, ( C S H 5 ) 2 C ~ and (C5H5)2Ni, and for their 1,l'-dimethyl derivatives. The metal 3d ionisation structure is discussed in terms of ligand field theory. The unusual spectrum of (CSH4Me)2 Mn is interpreted in terms of a high-spin/low-spin equilibrium in the gas phase.