SYNTHESIS AND PROPERTIES OF CATIONIC HYDRIDO(TERTIARY PHOSPHINE)RUTHENIUM(II) COMPLEXES

The cationic complex cis-[RuH(NH3)(PMe(3))(4)]PF6 can be synthesized from cis- RuH2(PMe(3))(4) and 1 equiv of NH4PF6 in Et(2)O. An excess of NH4PF6 leads to the formation ofthe dicationic species cis-[Ru(NH3)(2)(PMe(3))(4)][PF6](2). The NH3 ligand in cis-[RuH(NH3)(PMe(3))(4)]PF6 can be readily replaced by an appropriate ligand to give monohydrido complexes of the type cis[RuH(L)(PMe(3))(4)][PF6](2) (L = CH3CN, CO, PMe(3)). Whereas the substitution of the NH3 ligand with ethene or tolane was not possible, the reaction of cis-[RuH(NH3)(PMe(3))(4)]PF6 with a terminal alkyne such as phenylacetylene leads to the formation of styrene and cis- [Ru-(C=CPh)(NH3)(PMe(3))(4)]PF6. The neutral dihydrido complex cis-RuH2(PMe(3))(4) reacts with terminal alkynes HC=CR to give bis(alkynyl) complexes trans-Ru(C=Cr)(2)(PMe(3))(4) (R = Ph, SiMe(3), CO(2)Me). An NMR study of the reaction indicated involvement of intermediates cis-RuH(C=CR)(PMe(3))4 and cis-Ru(C=CR)(2)(PMe(3))(4). The cationic complexes cis- [RuH-(NH3)(PMe(3))(4)]PF6 and cis-[Ru(C=CPh)(NH3)(PMe(3))(4)]PF6 catalyze dimerization of the alkyne to give mainly (Z)-1,4-diphenylbuten-3-yne.