CRYSTAL AND MOLECULAR-STRUCTURE OF PENTAPHENYL-[TRIS(TRIMETHYLSILYL)METHYL]DIPLUMBANE

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.