SYNTHESIS, STRUCTURE, AND REACTIVITY OF GROUP-4 METALLOCENE TELLUROLATES - X-RAY CRYSTAL-STRUCTURES OF CP2ZR[TESI(SIME3)3]2, CP'2TI[TESI(SIME3)3]2, CP2ZR(ETA-2-COME)[TESI(SIME3)3], AND CP2TI[TESI(SIME3)3]PME3

Treatment of Cp2MCl2 (Cp = eta5-C5H5; M = Ti, Zr, Hf) with 2 equiv of (THF)2LiTeSi(SiMe3)3 produces the bis-tellurolates Cp2M[TeSi(SiMe3)3]2 (M = Ti (1), Zr (2), Hf (3)) in high yields. For titanium, the Cp' (Cp' = eta5-C5H4Me) derivative (4) was also prepared. The X-ray structures of 2 and 4 were determined and are presented for comparison. Tellurolysis of Cp2ZrMe2 with 1 equiv of HTeSi(SiMe3)3 gave Cp2Zr(Me)[TeSi(SiMe3)3](5); treatment with a second equiv of tellurol produced 2, again in high yield. Addition of CO to the methyl tellurolate 5 formed the acyl derivative Cp2Zr(eta2-COMe)[TeSi(SiMe3)3](6). Treatment of Cp2MCl2 with the alkyl tellurolate reagent (THF)3-LiTeC(SiMe3)3 leads to unstable complexes, Cp2M[TeC(SiMe3)3]2 (M = Ti (7), Zr (8)), which extrude elemental tellurium between -60 and -20-degrees-C to form alkylmetallocene complexes Cp2M[C(SiMe3)3]2 (M = Ti (9), Zr (10)); the latter species are unstable at room temperature and subsequently decompose giving the alkane HC(SiMe3)3 and unidentified metal products. Quantitative reduction to Ti(III) species occurred on addition of Lewis bases to 1 resulting in formation Of Cp2Ti[TeSi(SiMe3)3]L (L = PMe3 (11), PEt3 (12), PMe2Ph (13), 2,6-Me2C6H3NC (14)). These reduced species were prepared independently from [Cp2TiCl]2 using (THF)2LiTeSi(SiMe3)3 and the appropriate ligand. The X-ray crystal structure of 11 has also been determined. Treatment of 1 with CO gave [TeSi(SiMe3)3]2 and Cp2Ti(CO)2. Reaction of 1 with CO2 and CS2 also produced the ditelluride along with the titanium(III) carbonate {[Cp2Ti]2(CO3)}2 and the tetrathiolene titanium(IV) complex [Cp2Ti]2(C2S4), respectively. Crystallographic data for 2,4,6, and 11 are as follows. 2: orthorhombic, Pnna, a = 10.320(2) angstrom, b = 29.828(6) angstrom, c = 15.200(3) angstrom, R = 0.0311, R(w) = 0.0306. 4: monoclinic, C2/c, a = 28.3996(3) angstrom, b = 11.0404(4) angstrom, c = 15.3397(3) angstrom, beta = 93.49(3)degrees, R = 0.0349, R(w) = 0.0511. 6: monoclinic, P2(1)/c, a = 31.209(5) angstrom, b = 13.806(3) angstrom, c = 13.834(3) angstrom, beta = 91.741(13)degrees, R = 0.0309, R(w) = 0.0355. 11: monoclinic, P2(1)/c, a = 18.797(4) angstrom, b = 13.169(2) angstrom, c = 25.414(5) angstrom, beta = 91.969(18)degrees, R = 0.0473, R(w) = 0.0432.