C-H BOND ACTIVATION OF BENZENE AND CYCLIC ETHERS BY TPIR(III) SPECIES

The bis(ethylene) complex [Tp(Me)Ir(C2H4)(2)] (I) successively activat es C-H bonds in two molecules of benzene to generate a mixture of the bis(phenyl) complexes [Tp(2)(Me)Ir(C6H5)(2)N-2] (4) and [Tp(2)(Me)Ir(C 6H5)(2)](2)(mu-N-2) (5). They contain a coordinated molecule of dinitr ogen that acts as a terminal ligand in the former and as a bridge betw een the two metal centres in the latter. Compound lis also capable of activating regioselectively the two alpha-C-H bonds of the -OCH2- func tionality of THF to produce the Fischer carbene derivative [Tp(2)(Me)I rH-(CH2CH2CH2,CH3)(=C(CH2)(3)O)] (13). Compounds 4 and 5 are unusual e xamples of stable Ir-III-N-2 compounds, whereas 13, and other related complexes described in the paper, are distinctive species that contain a hydride, an alkyl and a carbene functionality bound to the same met al centre. Trapping experiments with PMe3 as the trapping reagent and isotopic labelling studies (H-2) provide useful mechanistic informatio n on the reaction pathway that leads to 4 land 5). This is compared wi th the sequence of events that yield complex 13. In each case the poss ibility of Tp(2)(Me)Ir(v) intermediates or transition states is consid ered.