Reactivity and Regioselectivity of Insertion of Unsaturated Molecules into M−C (M = Ir, Rh) Bonds of Cyclometalated Complexes

The reactivity of four different cyclometalated iridium and rhodium complexes (<b>1</b>, Ir−N−Me; <b>2</b>, Rh−N−Me; <b>3</b>, Ir−N−Py; <b>4</b>, Rh−N−Py) with ancillary ligands with different electronic and steric properties has been investigated by reactions of ethylene (<b>a</b>), propylene (<b>b</b>), carbon monoxide (<b>c</b>), <i>tert</i>-butylisocyanide (<b>d</b>), acetylene (<b>e</b>), and phenylacetylene (<b>f</b>). Only coordination products were obtained for the reactions of ethylene and propylene with <b>1</b> and <b>3</b>, while inserted and rearranged products were achieved for the reactions with <b>2</b> and <b>4</b>. Insertion of a single equivalent of acetylene was observed for the reactions with <b>2</b>, <b>3</b>, and <b>4</b>, whereas reaction with <b>1</b> produces a product in which 4 equiv of acetylene has undergone insertion. The reactions with carbon monoxide showed clean M−C bond insertion products, while <i>tert</i>-butylisocyanide formed only terminal adducts. Two equivalents of phenylacetylene were observed to insert for all of the cyclometalated complexes. The regioselectivity was also investigated for each cyclometalated complex by using a series of internal unsymmetrical alkynes, and the results revealed that the regioselectivity was controlled by both steric and electronic factors. The insertion compounds were fully characterized by <sup>1</sup>H NMR spectroscopy, <sup>13</sup>C NMR spectroscopy, elemental analysis, and X-ray determinations for selected cases.