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, {[(Me2N)C(N i Pr)2] 2Ti}2(N2) (2), was synthesized by reduction of the dichloride precursor, [(Me2N)C(N i Pr)2] 2TiCl2 (1). The dinitrogen complex reacts with phenyl azide to yield the titanium imido complex, [(Me2N)C(N i Pr)2]2TiNPh (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.