Synthesis and reductive N-N bond cleavage of neutral and cationic titanium(1-pyridinio)imido complexes

Novel (1-pyridinio)imidotitanium(IV) complexes [Cp'TiCl2(NNC5H3R2-2,6)] (3a , Cp' = Cp, R = H; 3b, Cp' = Cp, R = Me; 3c, Cp' = Cp*, R = Me) were synthe sized in high yield from [Cp'TiCl3] and [NH2NC5H3R2-2,6][PF6] in the presen ce of base. Complex 3b could also be prepared from [Cp2TiCl2] and [NH2NC5H3 Me2-2,6][PF6] in the presence of 1 equiv of BuLi. Cationic complexes [Cp*Ti (OTf)(NNC5H3Me2-2,6)(bpy)][OTf] (bpy = 2,2'-bipyridine) (4) and [Cp*Ti(NNC5 H3Me2-2,6)(terpy)][OTf](2) (terpy = 2,2':6',2 "-terpyridine) (5) were deriv ed from 3c through reaction with AgOTf in the presence of bpy and terpy, re spectively. The structures of complexes 3a, 3b, 3c, and 5 were determined b y X-ray crystallography. The N-N bond of 3a-c could be cleaved by reduction with sodium amalgam, liberating the corresponding pyridines in high yield, while the N-N bond in 4 and 5 could be reductively cleaved by cobaltocene in moderate yield. The N-N bond in 3a-c could also be cleaved by cobaltocen e in the presence of a proton analogue like Me3SiCl.