Crystal and molecular structure of pentaphenyl-[tris(trimethylsilyl)methyl]diplumbane

Abstract

The reaction of PbPh₂Cl₂ with two equivalents of Li[C(SiMe₃)₃] gave the diplumbane, Ph₃Pb–Pb-[C(SiMe₃)₃]Ph₂ instead of the expected Pb[C(SiMe₃)₃]₂Ph₂. A crystal-structure determination confirmed the presence of a Pb–Pb bond and the arrangement of the six substituents suggested that considerable steric strain between the C(SiMe₃)₃ group and the phenyls is present. Force-field calculations indicate that the structure of the expected product, Pb[C(SiMe₃)₃]₂Ph₂, may be severely distorted due to the presence of the two bulky groups. Possible steps in the formation pathway leading to the observed product, involving a phenyl group migration and radical coupling to give a Pb–Pb bond are discussed.