Reactions of a triazacyclononane-supported tantalum-lithium bridging alkylidene with organic substrates

The reactivity of a range of electrophilic organic substrates with a heterobimetallic tantalum-lithium bridging alkylidene [(Me3SiCH2)(ArN=)Ta(mu-CHSiMe3)(mu-eta(1):eta(3)-Pr-i(2)-tacn)-Li, 3] is presented. Proton sources of widely varying acidity react to protonate the alkylidene ligand, leading to an interesting tantalum-lithium bridging hydride complex in the case of H-2. The alkylidene 3 undergoes a series of insertion reactions with unsaturated substrates, such as acetonitrile, carbon monoxide, and carbon disulfide; it also reacts with an acid chloride to yield a tantalum enolate species featuring return of the Pr-i(2)-tacn(-) ligand to a tridentate coordination mode. The incorporated lithium in 3 played an important role, at least structurally, in the chemistry observed.