Alkyne insertion into cyclometallated pyrazole and imine complexes of iridium, rhodium and ruthenium; relevance to catalytic formation of carbo- and heterocyclesBased on the presentation given at Dalton Discussion No. 12, 13-15th September 2010, Durham University, UK.Electronic supplementary information (ESI) available: Figures showing structures of 3b,c and Table of crystallographic data for 3b,c. CCDC reference numbers 772790-772800. For ESI and crystallographic data in CIF or other electronic

The cyclometallated complexes [MCl(C^N)(ring)] (HC^N = 2-phenylpyrazole, M = Ir, Rh ring = Cp*; M = Ru, ring = p -cymene) readily undergo insertion reactions with RC&z.tbd;CR (R = CO 2 Me, Ph) to give mono insertion products, the rhodium complex also reacts with PhC&z.tbd;CH regiospecifically to give an analogous product. The products of the reactions of the cyclometallated imine complexes [MCl(C^N)Cp*] (HC^N = PhCH&z.dbd;NR, R = Ph, CH 2 CH 2 OMe, Me; M = Ir, Rh) with PhC&z.tbd;CPh depend on the substituent R; when R = CH 2 CH 2 OMe a monoinsertion is observed, however for R = Me the initial insertion product is unstable, undergoing reductive elimination with loss of the organic fragment, and for R = Ph no metal-containing product is isolated. With PhC&z.tbd;CH the cyclometallated imine complexes can give mono or di-insertion products. The implications for catalytic synthesis of carbo- and heterocycles by a tandem C-H activation, alkyne insertion mechanism are discussed. Intermediates of relevance to the catalytic synthesis of carbocycles and heterocycles via CH activation and alkyne insertion have been isolated. Factors affecting the product selectivity are discussed.