Reactivity of a titanium dinitrogen complex supported by guanidinate ligands: investigation of solution behavior and a novel rearrangement of guanidinate ligands.

The titanium dinitrogen complex, [[(Me(2)N)C(N(i)Pr)(2)]( 2)Ti](2)(N(2)) (2), was synthesized by reduction of the dichloride precursor, [(Me(2)N)C(N(i)Pr)(2)](2)TiCl(2) (1). The dinitrogen complex reacts with phenyl azide to yield the titanium imido complex, [(Me(2)N)C(N(i)Pr)(2)](2)TiNPh (3). The fluxional behavior of the guanidinate ligands in compounds 1-3 was investigated using variable temperature and two-dimensional NMR techniques; guanidinate ligand rotation and racemization reactions were observed. Rearrangement of the guanidinate ligand to an asymmetrical bonding mode utilizing the dimethylamino and amide-nitrogen atoms is observed in the bridging oxo and sulfido derivatives (4 and 5). These compounds are formed by the reactions of 2 with pyridine N-oxide and propylene sulfide, respectively. The ligand rearrangement was observed to be reversible for the bridging sulfido complex 5; the structure of this compound is sensitive to temperature and solvent. The solid-state and solution structures of compounds 1-5 are discussed.