SYNTHESIS, STRUCTURE, AND REACTIVITY OF HOMOLEPTIC TIN(II) AND LEAD(II) CHALCOGENOLATES AND THEIR CONVERSION TO METAL CHALCOGENIDES - X-RAY CRYSTAL-STRUCTURES OF (SN[TESI(SIME3)3]2)2 AND (PME3)SN[TESI(SIME3)3]2

The preparation and characterization of homoleptic tin(II) and lead(II) tellurolates, selenolates, and thiolates incorporating bulky ESi(SiMe3)3 ligands (E = Te, Se, S) are described. The derivatives M[ESi(SiMe3)3]2 (M = Sp: 1, E = Te; 3, E = Se; 5, E = S. M = Pb: 2, E = Te; 4, E = Se; 6, E = S) are prepared via protonolysis of M[N(SiMe3)2]2 with HESi(SiMe3)3. X-ray diffraction shows 1 to be dimeric in the solid state; it crystallizes in the space group P2/c with a = 14.536(2) angstrom, b = 9.3 10(1) angstrom, c = 29.605(6) A, beta = 97.72(1)degrees, V = 3970.2(19) angstrom3, Z = 4, R = 3.73%, and R(w) = 3.85%. Reaction of 1 with PMe3 affords the monomeric tin tellurolate (PMe3)Sn[TeSi(SiMe3)3]2 (10), while addition of 1 equiv of dmpe [dmpe = 1,2-bis(dimethylphosphino)ethane] to 1, 3, and 5 yields the dmpe-bridged stannyl chalcogenolates {Sn[TeSi(SiMe3)3]2}2(dmpe) (7, E = Te; 8, E = Se; 9, E = S). Complex 10 crystallizes in the space group P1BAR with a = 9.625(1) angstrom, b = 14.236(3) angstrom, c = 16.973(4) angstrom, alpha = 100.59(2)degree, beta = 103.95(2)degree, gamma = 91.48(1)degree, V = 2212.5(16) angstrom3, Z = 2, R = 3.56%, and R(w) = 4.52%. Pyrolysis of 1, 2, and 4 at relatively low temperatures (ca. 250-degrees-C) under N2 affords the cubic solids SnTe, PbTe, and PbSe and a single byproduct E[Si(SiMe3)3]2(E = Te, Se). The composition and crystallinity of these solids were confirmed by elemental analysis and X-ray powder diffraction. Related decomposition reactions also occur at even lower temperatures by thermolysis, UV irradiation, or addition of Lewis bases to hydrocarbon solutions.