C-F Bond Activation of P(C6F5)3 by Ruthenium Dihydride Complexes: Isolation and Reactivity of the "Missing" Ru(PPh3)3H(halide) Complex, Ru(PPh3)3HF.

The major product of the reaction between Ru(IMe4)2(PPh3)2H2 (1; IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) and P(C6F5)3 (PCF) is the five-coordinate complex Ru(IMe4)2(PF2{C6F5})(C6F5)H (2), which is formed via a complex series of C-F/P-C bond cleavage and P-F bond formation steps. In contrast, hydrodefluorination of all six ortho C-F bonds in PCF occurs with Ru(PPh3)4H2 to afford Ru(PPh3)3HF (3). NaBArF4 abstracted the fluoride ligand in 3 to give [Ru({η6-C6H5}PPh2)(PPh3)2H][BArF4], while B2pin2 reacted with 3 in C6D6 to yield a mixture of [Ru({η6-C6D6)(PPh3)2H]+ and Ru(PPh3)4H2. The treatment of 3 with HBpin (5 equiv) and HSiR3 (R = Et, Ph; 2 equiv) afforded Ru(PPh3)3(σ-HBpin)H2 and Ru(PPh3)3(SiR3)3H3, respectively. No stable substitution products were generated when 3 was reacted with Me3SiX (X = CF3, C6F5).

Ni(I) and Ni(II) ring-expanded N-heterocyclic carbene complexes: C-H activation, indole elimination and catalytic hydrodehalogenation.

Reaction of the bulky 6-membered N-heterocyclic carbene 6-Mes with Ni(cod)(2) gives a C-H activated 6-Mes nickel(II) complex, but the novel three-coordinate Ni(I) species Ni(6-Mes)(PPh(3))Br if the reaction is performed in the presence of Ni(PPh(3))(2)Br(2). The Ni(I) complex is a precursor for the catalytic hydrodehalogenation of aryl halides.