Dehydrogenation of Saturated CC and BN Bonds at Cationic N-Heterocyclic Carbene Stabilized M(III) Centers (M = Rh, Ir)

摘要: Chloride abstraction from the group 9 metal bis(N-heterocyclic carbene) complexes M(NHC)2(H)2Cl [M = Rh, Ir; NHC IPr N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene or IMes N,N′-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] leads to formation of highly reactive cationic species capable dehydrogenation saturated CC and BN linkages. Thus, reaction Ir(IPr)2(H)2Cl (1) with Na[BArf4] in fluorobenzene generates [Ir(IPr)2(H)2]+[BArf4]− (4) which iridium center is stabilized by a pair agostic interactions utilizing methyl groups isopropyl substituents. After prolonged period C−H activation occurs, ultimately leading one carbene iPr substituents [Ir(IPr)(IPr′′)(H)2]+[BArf4]− (5), featuring mixed NHC/alkene donor IPr′′ ligand. By contrast, related M(IMes)2(H)2Cl (M Ir), feature lacking β-hydrogens, react give rar...