Generation of Dimethylsilylene and Allylidene Holmium Complexes from Trimethylsilylated Allyl Ligands

The reaction of K[1,3-(SiMe3)2C3H3] with partially hydrated holmium triflate leads to a dimeric complex (1) in which hydrogen abstraction from a trimethylsilyl group has occurred on two allyl ligands, forming dimethylsilylene units that bridge the holmium atoms. When the reaction time is prolonged, a different product (2) is isolated, in which in addition to two dimethylsilylene bridges, the metal centers are joined with a μ-η,η3-allylidene ligand. Both crystallographic and computational studies provide evidence for delocalized bonding in the allylidene fragment.