Synthesis, Structural Characterization, and Reactivity of Group 4 Metal Complexes Derived from 1-Indenyl-1,2-carborane

Treatment of 1-indenyl-1,2-carborane with 1 equiv of M(NMe2)4 (M = Zr, Hf) in toluene gave [η5-(C2B10H11)C9H6]M(NMe2)3 (2), which were converted to [η5-(C9H7)C2B9H10]M(NMe2)2(HNMe2) (3) in the presence of HNMe2. Complexes 3 were also prepared from an equimolar reaction of [Me3NH][7-C9H7-7,8-C2B9H11] (4) with M(NMe2)4. Dissolving 2 or 3 in polar solvents led to the isolation of structurally unique complexes [σ:η5-(C9H6)C2B9H10]M(NMe2)(L)n (M = Ti, L = DME, n = 1 (5a); M = Zr, L = DME, n = 1 (5b), L = Py, n = 2 (5b′), L = THF, n = 2 (5b′′)). Interaction of 3 with 1 or 2 equiv of diisopropylcarbodiimide yielded the monoguanidinate complex [η5-(C9H7)C2B9H10]Zr(NMe2)[η2-(PriN)2C(NMe2)] (9) or diguanidinate complex [η5-(C9H7)C2B9H10]Zr[η2-(PriN)2C(NMe2)]2 (10). Heating 9 in toluene gave a C−N bond cleavage product, [η1:σ:η5-{[2-CNPri(NHPri)]C9H5}C2B9H10]Zr[η2-(PriN)2C(NMe2)] (11a). Triguanidinate complexes [{η2-(PriN)2C(NR2)}3M][(C9H7)C2B9H11] (8) (M = Ti, Zr, Hf; NR2 = NMe2, NEt2, N(CH2)4) were prepared from reactions of 3 or 5b with 3 equiv of guanidines in refluxing THF. Treatment of 5b with 1 equiv of diphenylketene generated [σ:η5-{[3-C(CPh2)-O]C9H6}C2B9H10]Zr(NMe2)(THF)2 (14). These complexes were fully characterized by various spectroscopic techniques and elemental analyses. Some were further confirmed by single-crystal X-ray analyses.