5. "Synthesis, Structure, and Deprotonation of a Mesitylphosphido-Bridged Cyclopentadienylnickel(II) Dimer," Stanislav V. Maslennikov, David S. Glueck, Glenn P. A. Yap, and Arnold L. Rheingold, Organometallics 1996, 15, 2483-2488.
The bridging phosphido complex [NiCp(µ-PHMes)]2 (1, Mes = 2,4,6-Me3C6H2) was prepared from NiCp 2 and PH2Mes. Deprotonation and methylation of 1 yields (NiCp)2(µ-PHMes)(µ-PMeMes) (4) and [NiCp(µ-PMeMes)] 2 (6) via observable anionic phosphinidene intermediates. NMR spectroscopy was used to characterize syn and anti isomers of 1, 4, and 6, and the structures of anti-1a and syn-6b were determined by X-ray crystallography.