Intramolecular C-H activation and oxidative addition reactions of iridium complexes containing arylamines with bulky asubstituents on nitrogen; X-ray structures of [IrI(C6H4CH2NEt2-2-C,N) (cod)] and [IrIII(C6H4CH2NEt(CHMe)-2-C,N,C')I(cod)](cid=cyclooacta-1,5-diene)

Abstract

Square-planar iridium(I) complexes [Ir(C{6}H{4}CH{2}NRR')(cod)] (R = R' = Et; R = Me, R' = t-Bu; cod = cycloocta-1, 5-diene) containing C,N-chelating arylamine ligands have been synthesized and characterized by NMR spectroscopy. An X-ray diffraction study of [Ir(C{6}H{4}CH{2}NEt{2}-2-C,N)(cod)] shows a weak agostic interaction between the d}8{ metal center and a methyl H atom of one ethyl group. An oxidative addition reaction of this complex with MeI affords an Ir(III) complex [Ir(C{6}H{4}CH{2}NEt(CHMe)-2-C,N,C')I(cod)] which results from an intramolecular methylene C-H activation process. This latter complex has been characterized with 2D NMR techniques and an X-ray diffraction study. The reactivity of the new iridium(I) complexes as well as [Ir(C{6}H{4}CH{2}NMe{2}-2-C,N)(cod)], [Ir(1-C{1}{0}H{6}NMe{2}-8-C,N)(cod)] and [Ir(C{6}H{4}CH{2}N(Me)CH{2}CH{2}NMe{2}-2-C,N)(cod)] towards H{2} is reported; the different products obtained are discussed with reference to reaction pathways influenced by the steric bulk on the nitrogen donor atom. Crystals of [Ir(C{6}H{4}CH{2}NEt{2}-2-C,N)(cod)] are triclinic, space group P1 with unit-cell dimensions a = 9.154(1), b = 9.992(1), c = 10.846(1)@?9 , @a = 93.46(1), @b = 113.03(1), @c = 109.84(1)}o{, Z = 2, final R = 0.0234, wR = 0.0295 for 3465 reflections with I>2.5@s(I) and 197 parameters. Crystals of [Ir(C{6}H{4}CH{2}NEt(CHMe)-2-C,N,C')I(cod)] are triclinic, space group P1 with dimensions a = 7.591(1), b = 11.406(1), c = 13.511(1) @?9, @a = 65.63(1), @b = 88.34(1), @c = 83.29(1)}o{, Z = 2, final R = 0.0319, wR = 0.0402 for 4236 reflections withI >2.5@s(I) and 228 parameters.