Synthesis and reactivity of the formally co-ordinatively unsaturated diruthenium hydride [Ru2(µ-H)(µ-CO)(CO)3{µ-(PriO)2PNEtP(OPri)2}2]+and its co-ordinatively saturated parent [Ru2H(CO)5{µ-(PriO)2PNEtP(OPri)2}2]+

Abstract

Protonation of the co-ordinatively unsaturated species [Ru2(µsb-CO)2(CO)2(µ-etipdp)2][sb = semi-bridging, etipdp =(PriO)2PNEtP(OPri)2] by acids of non-co-ordinating conjugate bases, e.g. HBF4·OEt2, produced [Ru2(µ-H)(µ-CO)(CO)3(µ-etipdp)2]+ which, as established X-ray crystallographically for the PF6– salt, contains both a bridging carbonyl and a bridging hydride ligand. This cationic species is very susceptible to attack by both neutral and anionic nucleophiles affording a range of product types. For instance, its reactions with anions X– which are capable of functioning as monodentate bridging ligands and which preferentially adopt the closed bridging co-ordination mode, e.g. halide and hydrogensulfide ions, afforded products of the type [Ru2(µ-X)H(µsb-CO)(CO)2(µ-etipdp)2](X = Cl, Br, I, SH, etc.), resulting from the substitution of a carbonyl group by the nucleophile. On the other hand, anionic nucleophiles such as H– and CN– gave addition products of the type [Ru2HX(CO)4(µ-etipdp)2](X = H, CN, etc.) in which the hydride and the X– ligand occupy equatorial sites trans disposed with respect to each other, as established in a separate study for [Ru2H2(CO)4(µ-etipdp)2]. Carbon monoxide also afforded a simple addition product, viz.[Ru2H(CO)5(µ-etipdp)2]+, but the majority of the other neutral nucleophiles studied, particularly the unsaturated systems, yielded products resulting from formal insertion of the nucleophile into the Ru–H bond. Thus sulfur produced [Ru2(µ-SH)(CO)4(µ-etipdp)2]+, while unsaturated nucleophiles of general formula X′Y′, e.g. PhCN and RCCH (R = H, Ph, etc.), gave products of the type [Ru2{µ-X′Y′(H)}(CO)4(µ-etipdp)2]+, e.g.[Ru2{µ-NC(H)Ph}(CO)4(µ-etipdp)2]+ or of the type [Ru2{µ-η2-X′Y′(H)}(CO)4(µ-etipdp)2]+, e.g.[Ru2(µ-η1 : η2-CHCHR)(CO)4(µ-etipdp)2]+. Heterocumulenes X″Y″Z″ such as CS2 and PhNCS behaved similarly affording products of general formula [Ru2{µ-η2-X″Y″(H)Z″}(CO)4(µ-etipdp)2]+ containing five-membered RuX″Y″Z″Ru rings. The co-ordinatively saturated pentacarbonyl [Ru2H(CO)5(µ-etipdp)2]PF6 gave products similar to those afforded by [Ru2(µ-H)(µ-CO)(CO)3(µ-etipdp)2]PF6 on reaction with systems of the type X′Y′ and X″Y″Z″ except that, for terminal alkynes such as PhCCH, alkenylcarbonyl-bridged products, e.g.[Ru2{µ-η2-OC(CHCHPh)}(CO)4(µ-etipdp)2]PF6, are produced. The crystal structures of the following compounds were determined : [Ru2(µ-H)(µ-CO)(CO)3(µ-etipdp)2]PF6, [Ru2(µ-I)H(µsb-CO)(CO)2(µ-etipdp)2], [Ru2{µ-N(CHPh)}(CO)4(µ-etipdp)2]PF6, [Ru2(µ-η1 : η2-CHCH2)(CO)4(µ-etipdp)2]PF6, [Ru2{µ-η2-OC(CHCHPh)}(CO)4(µ-etipdp)2]PF6 and [Ru2{µ-η2-SC(H)NPh}(CO)4(µ-etipdp)2]PF6.