Inorganic Chemistry, Vol.42, No.15, 4759-4772, 2003
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 Bu-t): Synthesis, characterization, and reactions with weakly acidic C-H bonds
The octahedral Ru(II) amine complexes [TpRu(L)(L')(NH2R)][OTf] (L = L' = PMe3, P(OMe)(3) or L = CO and L' = PPh3;, R = H or Bu-t) have been synthesized and characterized. Deprotonation of the amine complexes [TpRu(L)(L')(NH3)][OTf] or [TpRu(PMe3)(2)((NH2Bu)-Bu-t)][OTf] yields the Ru(II) amido complexes TpRu(L)(L')(NH2) and TpRu(PMe3)(2)((NHBu)-Bu-t). Reactions of the parent amido complexes or TpRu(PMe3)(2)((NHBu)-Bu-t) with phenylacetylene at room temperature result in immediate deprotonation to form ruthenium-amine/phenylacetylide ion pairs, and heating a benzene solution of the [TpRu(PMe3)(2)((NH2Bu)-Bu-t)][PhC2] ion pair results in the formation of the Ru(II) phenylacetylide Bu-t)][PhC2] converts to the complex TpRu(PMe3)(2)(CdropCPh) in >90% yield. The observation that [TpRu(PMe3)(2)(NH2 Ru(II) acetylide with good yield while heating the ion pairs [TpRu(L)(L')(NH3)][PhC2] yields multiple products is attributed to reluctant dissociation of ammonia compared with the (t)butylamine 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 TpRuL(2)(NHPh) {L = PMe3 or P(OMe)(3)} react with 10 equiv of phenylacetylene at elevated temperature to produce Ru(II) acetylide complexes TpRuL(2)(CdropCPh) 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)(L')(NH2) (L = L' = PMe3 or L = CO and L' = PPh3) or TpRu(PMe3)(2)((NHBu)-Bu-t) at elevated temperatures result in the formation of benzene and Ru hydride complexes. TpRu(PMe3)(2)(H), [Tp(PMe3)(2)Ru C=C(H)Ph][OTf], [Tp(PMe3)(2)Ru=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=CPh) are reported.