Reactivity of Low-Valent Iridium, Rhodium, and Platinum Complexes with Di- and Tetrasubstituted Hydrazines
datasetposted on 26.05.2008, 00:00 by Jessica M. Hoover, John Freudenthal, Forrest E. Michael, James M. Mayer
Three complexes, IrCl(PEt3)3, Rh(NNN)Cl (NNN = 2,6-(CyNCH)2C5H3N), and (NN)PtMe2 [NN = 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy)], have been investigated for N−N oxidative addition reactivity with di- and tetrasubstituted hydrazines. The reaction of IrCl(PEt3)3with 1,2-diphenylhydrazine (PhNHNHPh) forms the cyclometalated azobenzene complex (Et3P)2Cl(H)Ir(C6H4NNPh) (1) and the 2:1 complex [(Et3P)2Cl(H)Ir]2(μ-C6H4NNC6H4) (2). The Rh(NNN)Cl pincer complex catalyzes the disproportionation of PhNHNHPh to azobenzene and aniline with no change in the Rh complex. The reaction of (bpy)PtMe2 with the hydrazine AcNHNHC(O)CH2CH2CHCH2 (3) yields the platinum metallacycle (bpy)Pt(η2-AcN-NC(O)(CH2)2CHCH2 (4). Although IrCl(PEt3)3, Rh(NNN)Cl, and (NN)PtMe2 all undergo facile oxidative addition of other X−Y bonds, such reactivity is not observed for hydrazines; in the Ir and Pt systems there is a clear preference for cleavage of the stronger N−H bond over the N−N bond. The tetrasubstituted hydrazines tetraphenylhydrazine, 1,2-diphenyl-1,2-dimethylhydrazine, bisuccinimide, biphthalimide, and N-dimethylamino phthalimide do not react with IrCl(PEt3)3, Rh(NNN)Cl, and (NN)PtMe2. This lack of reactivity appears to be due to kinetic rather than thermochemical factors.