Oxidative Addition and Reductive Elimination Reactions oftrans-[Ir(PPh3)2(CO)(NC4H4)] andtrans,cis-[Ir(PPh3)2(H)2(CO)(NC4H4)], Including N−H Bond-Forming Reductive Elimination of Pyrrole

Abstract

The complex trans-(PPh3)2(CO)Ir(NC4H4) (1) has been synthesized and is an analogue of metal−aryl complexes, but with a nitrogen of the heteroaromatic group covalently bonded to the transition metal. Compound 1 readily undergoes initial reaction with a variety of substrates at the metal center rather than at the pyrrolyl nitrogen, allowing for the study of reactions between the pyrrolyl group and accompanying covalent ligands. These reactions ultimately produce N-substituted pyrroles, X-NC4H4 (X = C(O)CH3, C(O)C6H4CH3, H, SnMe3, SiMe3, SiEt3, Bcat). Compound 1 undergoes oxidative addition of H2 to form the stable Ir(III) product (PPh3)2(CO)Ir(H)2(NC4H4) (2). When pure 2 is heated, it undergoes simple elimination of H2 to regenerate 1; however, if 2 is heated for longer times under H2 in the presence of PPh3, it undergoes reductive elimination of pyrrole and forms (PPh3)3(CO)Ir(H). Qualitative analysis of the mechanism of this reaction suggests that it occurs by either direct reductive elimination from the ...