(Tris(trimethylsilyl)silyl)lead(IV) derivatives

Article abstract of DOI:10.1021/ic00057a019

The reaction of Ph₃PbCl with 1 equiv of (THF) ₃LiSi(SiMe₃)₃ in ether afforded Ph ₃PbSi(SiMe₃)₃ in high yield. Our attempts to prepare Ph₂Pb(Si(SiMe₃)₃)₂ through a similar reaction of Ph₂PbCl₂ with 2 equiv of (THF) ₃LiSi(SiMe₃)₃ gave a mixture of the expected product, a pale yellow solid, and [Ph₂PbSi(SiMe₃) ₃]₂, a bright yellow-orange, thermochromic solid. These products were separated by fractional crystallization from the reaction mixture and characterized by their elemental analyses, NMR spectra (¹H, ¹³C), and infrared and UV-visible spectra. In order to compare [Ph₂PbSi(SiMe₃)₃]₂ with its previously reported digermane counterpart, an X-ray structure determination was carried out on the product as a benzene monosolvate. Crystals of [Ph ₂PbSi(SiMe₃)₃]₂ were monoclinic, P2₁/n, with a = 13.208(2) A, b 16.586(3) A, c = 13.896(3) A, β = 99.29°, V = 3004 A³, and Z = 2. The molecular structure confirmed that the product is indeed a diplumbane exhibiting a Pb-Pb bond 2.911(1) A in length. All three products were unreactive toward atmospheric moisture. NMR studies of Ph₂Pb(Si(SiMe ₃)₃)₂ and [Ph₂PbSi(SiMe ₃)₃]₂ solutions in ether showed the former to be stable for at least 22 h while the latter decomposed completely within the same period.