Isolation and Characterization of a Monomeric Cationic Titanium Hydride

摘要

Organotitanium hydrides are a highly reactive class of compounds that have been implicated in a variety of catalytic processes, including olefin hydrogenation and hydrosilation and silane dehydrocoupling. Despite their importance, isolated, terminal titanium hydrido compounds are restricted to a few Ti(III) examples or highly sterically protected neutral Ti(IV) derivatives. Cationic variants are even more rare, but presumably play a critical role in olefin polymerization and oligomerization reactions, especially where H_2 is used as a polymer MW controlling agent. Given the tendency of Ti(IV) hydrides to undergo reduction to Ti(III) via loss of H_2, it is of interest to probe the behavior of cationic titanium hydrides in ligand environments relevant to olefin polymerization, because reductive side reactions might be expected to impact overall catalyst performance. Here, we report reactions of the catalysts [Cp(~tBu_3PN)TiCH_3]~+[B(C_6F_5)_4]~- (Cp = C_5H_5, 1-Cp; C_5Me_5, 1-Cp~*) with H_2 and detail the complete characterization of a monomeric cationic organotitanium hydride.