Octahedral Ru(II) Amido Complexes TpRu(L)(L)(NHR) (Tp = Hydridotris(pyrazolyl)borate; L = L = P(OMe)3 or PMe3 or L = CO and L = PPh3; R = H, Ph, or tBu): Synthesis, Characterization, and Reactions with Weakly Acidic C-H Bonds

The octahedral Ru(II) amine complexes [TpRu(L)(Lʹ)(NH2R)][OTf] (L = Lʹ = PMe3, P(OMe)3 or L = CO and Lʹ = PPh3; R = H or tBu) have been synthesized and characterized. Deprotonation of the amine complexes [TpRu(L)(Lʹ)(NH3)][OTf] or [TpRu(PMe3)2(NH2tBu)] [OTf] yields the Ru(II) amido complexes TpRu(L)(Lʹ)(NH2) and TpRu(PMe3)2(NHtBu). Reactions of the parent amido complexes or TpRu(PMe3)2(NHtBu) with phenylacetylene at room temperature result in immediate deprotonation to form rutheniumamine/phenylacetylide ion pairs, and heating a benzene solution of the [TpRu(PMe3)2(NH2tBu)][PhC2] ion pair results in the formation of the Ru(II) phenylacetylide complex TpRu(PMe3)2(C(identical)CPh) in >90% yield. The observation that [TpRu(PMe3)2(NH2tBu)] [PhC2] converts to the Ru(II) acetylide with good yield while heating the ion pairs [TpRu(L)(Lʹ)(NH3)][PhC2] yields multiple products is attributed to reluctant dissociation of ammonia compared with the tbutylamine ligand (i.e., different rates for acetylide/amine exchange). These results are consistent with ligand exchange reactions of Ru(II) amine complexes [TpRu(PMe3)2(NH2R)][OTf] (R = H or tBu) with acetonitrile. The previously reported phenyl amido complexes TpRuL2(NHPh) {L = PMe3 or P(OMe)3} react with 10 equiv of phenylacetylene at elevated temperature to produce Ru(II) acetylide complexes TpRuL2(C(identical)CPh) in quantitative yields. Kinetic studies indicate that the reaction of TpRu(PMe3)2(NHPh) with phenylacetylene occurs via a pathway that involves TpRu (PMe3)2(OTf) or [TpRu(PMe3)2(NH2Ph)][OTf] as catalyst. Reactions of 1,4-cyclohexadiene with the Ru(II) amido complexes TpRu(L) (Lʹ)(NH2) (L = Lʹ = PMe3 or L = CO and Lʹ = PPh3) or TpRu(PMe3)2(NHtBu) at elevated temperatures result in the formation of benzene and Ru hydride complexes. TpRu(PMe3)2(H), [Tp(PMe3)2Ru=C=C(H)Ph][OTf], [Tp(PMe3)2Ru=C(CH2Ph){N(H)Ph}][OTf], and [TpRu (PMe3)3][OTf] have been independently prepared and characterized. Results from solid-state X-ray diffraction studies of the complexes [TpRu(CO)(PPh3)(NH3)][OTf], [TpRu(PMe3)2(NH3)][OTf], and TpRu(CO)(PPh3)(C(identical)CPh) are reported.