SYNTHESIS AND CHARACTERIZATION OF NEW POLYNUCLEAR TITANIUM(IV) OXO ALKYLS - [CP-ASTERISK-TIR(MU-O)]3 AND [CP-ASTERISK-TI(MU-O)]3CIR2 - THERMOLYSIS OF [CP-ASTERISK-TIET(MU-O)]3 AND THE CRYSTAL-STRUCTURE OF THE 1ST (MU(3)-ETHYLIDYNE)TITANIUM COMPLEX, [CP-ASTERISK-TI(MU-O)]3(MU(3)-CME)

The oxo trimer [Cp*TiCl(mu-O)]3 (1) (Cp* = eta5-C5Mer5) reacts with organolithium LiR (R = Me, Ph, p-MeC6H4, C=Ph) or Grignard reagents ClMgR (R = Me, Et, Pr, CH2Ph, C=CH) to give the new alkyl oxo trimers [Cp*TiR(mu-O)]3 (2-9) and [Cp*Ti(mu-O)3ClR2 (10-12) in good yield. In the case of [Cp*TiEt3(mu-O)]3 (6), the thermal decomposition at temperatures in the range of 195-200-degrees-C leads to the preparation of the first example of a d0 (mu3-alkylidyne) complex, [Cp*Ti(mu-O)]3(mu3-CMe) (13). The structure of this complex has been proved unequivocally by X-ray diffraction studies (space group Pnma, a = 12.104(6) angstrom, b = 19.404(5) angstrom, c = 13.744(1) angstrom, Z = 4, R = 0.046, and R(w) = 0.050). The oxo cluster core of 13 can be described like a six membered ring, Ti3O3, where the three titanium atoms form an almost perfect equilateral triangle capped by mu3-ethylidyne ligand, with short nonbonded Ti...Ti contacts (average value of 2.82