Steric control of lanthanide coordination environment:: (TpMe2)2Sm(CCPh), a monomeric, base-free lanthanide alkynide complex, and its thermally induced transformation to (TpMe2){HB (Me2pz)2(CCPh)}Sm(Me2pz)

Reaction of Sm(Tp(Me2))(2) (1) with Hg(C=CPh)(2) in THF at ambient temperature afforded the monomeric, base-free lanthanide alkynide complex (Tp(Me2))(2)Sm(C=CPh) (2). Thermolysis of 2 in benzene resulted in clean transformation to the new complex: (Tp(Me2)){HB(Me(2)pz)(2)(C=CPh)}Sm(Me(2)pz) (3), the result of an interesting, rcplusual ligand rearrangement on the Sm(III) center. Conmplexes 2 and 3 have been fully characterized by spectroscopic methods and X-ray crystallography.