Synthesis and Characterization of New Polynuclear Titanium(IV) Oxo Alkyls: [Cp*TiR(.mu.-O)]3 and (Cp*Ti)3R2Cl(.mu.-O)3. Thermolysis of [Cp*TiEt(.mu.-O)]3 and the Crystal Structure of the First (.mu.3-Ethylidyne)titanium Complex [Cp*Ti(.mu.-O)]3(.mu.3-CMe)

The oxo trimer [Cp*TiCl(m-O)]3 (1) (Cp* = h5-C5Me5) reacts with organolithium LiR (R = Me, Ph, p-MeC6H4, CCPh) or Grignard reagents ClMgR (R = Me, Et, Pr, CH2Ph, CCH) to give the new alkyl oxo trimers [Cp*TiR(m-O)]3 (2-9) and [Cp*Ti(m-0)]3ClR2 (10-12) in good yield. In the case of [Cp*TiE3(m-0)]3 (6), the thermal decomposition at temperatures in the range of 195-200 OC leads to the preparation of the first example of a do (m3-alkylidyne) complex, [Cp*Ti(m-0)]3(m3-CMe) (13). The structure of this complex has been proved unequivocally by X-ray diffraction studies (space group Pnma, a = 12.104(6) A, b= 19.404(5) A, c = 13.744(1) A, Z = 4, R = 0.046, and Rw = 0.050). The oxo cluster core of 13 can be described like a six membered rhg, Ti303, where the three titanium atoms form an almost perfect equilateral triangle capped by a m3-ethylidyne ligand, with short nonbonded Ti···Ti contacts (average value of 2.82 A).