Contrasting reactivity behaviour of the [RuHCl(CO)(PNP)] complex with electrophilic reagents XOTf (X = H, CH3, Me3Si).

A new ruthenium pincer complex [RuHCl(CO)(PNP)] (PNP = PhCH2N(CH2CH2PPh2)2) () was synthesized and characterized. The reactivity of complex with electrophilic reagents XOTf (X = H, CH3, and Me3Si; OTf = CF3SO3) was studied by variable temperature NMR spectroscopy with an aim to observe and characterize sigma complexes of type [Ru(η(2)-HX)Cl(CO)(PNP)][OTf] (X = H (), CH3 (), Me3Si ()). Reaction of complex with HOTf resulted in the formation of the dihydrogen complex, [Ru(η(2)-H2)Cl(CO)(PNP)[OTf] (). On the other hand, the reaction between complex and MeOTf and Me3SiOTf resulted in the direct elimination of MeCl and Me3SiCl via a SN2 type of reaction without the intermediacy of the respective sigma complexes and . This contrasting reactivity behaviour has been rationalized taking into consideration the approach of the relatively bulky electrophiles CH3(+) and Me3Si(+) onto the hydride moiety of the ruthenium fragment, which is sterically hindered.