Monomeric And Dimeric Titanatranes

The synthesis and characterization of four new titanatranes Z-Ti(OCH2CH2)3N (Z = O-t-Bu (5), OPh (6), O2CMe (7), NMe2 (8) are reported. An X-ray crystal structure determination of 7 reveals a novel dimeric structure in which each titanium is seven-coordinate owing to alkoxide bridging and bidentate behavior of the acetate group. In contrast, the structure of 4 (Z = OSiPh3) determined by X-ray means is monomeric owing to the bulk of the apical siloxy group. Variable-temperature H-1 and C-13 NMR studies allow the categorization of the titanatranes studied into three classes: those displaying monomeric behavior in solution at room temperature (Z = O-i-Pr, (1), Cp (3), OSiPh3 (4), and O-t-Bu (5)), those behaving as dimers undergoing a fluxional gearing motion at room temperature but becoming monomeric upon warming (Z = Cl (2), 6, 7), and titanatrane 8, which behaves as a rigid dimer at room temperature. Crystallographic parameters for 4 are space group R3BAR, a = 9.5689 (5) angstrom, b = 45.411 (4) angstrom, Z = 6, while for 7 they are space group P2(1)/n, a = 15.563 (3) angstrom, b = 6.872 (1) angstrom, c = 19.743 (4) angstrom, beta = 106.65 (1)-degrees, Z = 2.