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The ability of the coordinatively saturated, 18-electron Cp*(H)Ru═CHR complex 1 to serve as a masked source of the coordinatively unsaturated Cp*Ru-CH2R species 2 via reversible α-hydride elimination was surveyed. The rate constant for this dynamic process (300 K, C6D6) was measured to be 59 ± 1 s−1, on the basis of data obtained from selective inversion NMR experiments. Exposure of 1 to an atmosphere of CO or to an equivalent of either PMe3 or PH2Ph afforded the corresponding 2·L adduct (L = CO, 98%; PMe3, 93%; PH2Ph, 67%). Treatment of 1 with Ph2SiH2, PhSiH3, Ph2SiClH, or PhSiClH2 afforded the corresponding net Si−H addition product, 3a−d (82−94%); an NMR spectroscopic investigation of the analogous reaction of 1 with Ph2SiD2 provided evidence in support of a reaction mechanism involving previously undocumented Si−H addition across the Ru═C unit in 1 in the formation of 3a. Addition of Jutzi’s acid (H(OEt2)2B(C6F5)4) to 1 resulted in the quantitative formation of 4 (the N-C-H cyclometalated variant of [...

Treatment of Cp*RuCl(kappa2-P,N-2b) (2b = 2-NMe2-3-PiPr2-indene) with TlSO3CF3 produced the cyclometalated complex [4]+SO3CF3- in 94% isolated yield. Exposure of [4]+X- (X = B(C6F5)4 or SO3CF3) to Ph2SiH2 (10 equiv) or PhSiH3 afforded the corresponding [Cp*(mu-P,N-2b)(H)2Ru=SiRPh]+X- complexes, [5]+X- (R = Ph; X = B(C6F5)4, 82%; X = SO3CF3, 39%) and [6]+X- (R = H; X = B(C6F5)4, 94%; X = SO3CF3, 95%). Notably, these transformations represent the first documented examples of Ru-mediated silylene extrusion via double geminal Si-H bond activation of an organosilane-a key step in the recently proposed Glaser-Tilley (G-T) alkene hydrosilylation mechanism. Treatment of [5]+B(C6F5)4- with KN(SiMe3)2 or [6]+SO3CF3- with NaN(SiMe3)2 afforded the corresponding zwitterionic Cp*(mu-2-NMe2-3-PiPr2-indenide)(H)2Ru=SiRPh complex in 69% (R = Ph, 7) or 86% (R = H, 8) isolated yield. Both [6]+X- and 8 proved unreactive toward 1-hexene and styrene and provided negligible catalytic turnover in the attempted metal-mediated hydrosilylation of these substrates with PhSiH3, thereby providing further empirical evidence for the required intermediacy of base-free Ru=Si species in the G-T mechanism. Isomerization of the P,N-indene ligand backbone in [6]+X-, giving rise to [Cp*(mu-1-PiPr2-2-NMe2-indene)(H)2Ru=SiHPh]+X- ([9]+X-), was observed. In the case of [9]+SO3CF3-, net intramolecular addition of the Ru=Si-H group across the styrene-like C=C unit within the ligand backbone to give 10 (96% isolated yield) was observed. Crystallographic characterization data are provided for [4]+X-, [5]+X-, [6]+X-, 8, and 10.

Ir silyl pincer complexes insert into the N-H bonds of anilines and ammonia under mild conditions to form isolable [Cy-PSiP]Ir(H)(NHR) complexes that are resistant to N-H bond reductive elimination at room temperature, even in the presence of arenes, alkenes, and phosphines.

The synthesis and reactivity of coordinatively unsaturated Rh and Ir complexes supported by the new bis(phosphino)silyl pincer ligand [kappa(3)-(2-Cy(2)PC(6)H(4))(2)SiMe](-) ([Cy-PSiP](-)) are reported, including the first example of facile, room temperature intermolecular arene C-H bond activation mediated by a silyl pincer complex.