Reactions of Cyclopentadienyl−Amidinate Titanium Hydrazides with CO2, CS2, and Isocyanates: Ti═Nα Cycloaddition, Cycloaddition−Insertion, and Cycloaddition−NNR2 Group Transfer Reactions

We report a comprehensive combined experimental and DFT investigation of the synthesis, molecular and electronic structures, and reactivity of terminal hydrazido complexes with CO2, CS2, isocyanates, and isothiocyanates. Reaction of Cp*Ti{MeC(NiPr)2}(NtBu) with hydrazines R1R2NNH2 gave the structurally characterized series of hydrazides Cp*Ti{MeC(NiPr)2}(NNR1R2) (R1 = Ph, R2 = Ph (13), Me (14); R1 = R2 = Me (15)). The energetics of this imide/hydrazine exchange reaction, as well as the electronic and molecular structures of 13−15, have been evaluated by DFT and compared with those of their methyl and phenyl imido counterparts. Reaction of 13−15 with CO2 or CS2 gave Ti═Nα cycloaddition products of the type Cp*Ti{MeC(NiPr)2}{N(NR2)C(E)E} (R = Ph, Me; E = O, S) and, in the case of CO2, cycloaddition−insertion products Cp*Ti{MeC(NiPr)2}{OC(O)N(NR2)C(O)O}, in which 2 equivs of CO2 had effectively inserted into Ti═Nα. Reaction of 13 with isocyanates and isothiocyanates also gave stable cycloaddition products. C...