Heterobimetallic Ti/Co Complexes That Promote Catalytic N-N Bond Cleavage

Abstract

Treatment of the tris(phosphinoamide) titanium precursor ClTi(XylNPiPr2)3 (1) with CoI2 leads to the heterobimetallic complex (η2-iPr2PNXyl)Ti(XylNPiPr2)2(μ-Cl)CoI (2). One-electron reduction of 2 affords (η2-iPr2PNXyl)Ti(XylNPiPr2)2CoI (3), which can be reduced by another electron under dinitrogen to generate the reduced diamagnetic complex (THF)Ti(XylNPiPr2)3CoN2 (4). The removal of the dinitrogen ligand from 4 under vacuum affords (THF)Ti(XylNPiPr2)3Co (5), which features a Ti-Co triple bond. Treatment of 4 with hydrazine or methyl hydrazine results in N-N bond cleavage and affords the new diamagnetic complexes (L)Ti(XylNPiPr2)3CoN2 (L = NH3 (6), MeNH2 (7)). Complexes 4, 5, and 6 have been shown to catalyze the disproportionation of hydrazine into ammonia and dinitrogen gas through a mechanism involving a diazene intermediate.