Synthesis and reactivity of the unsaturated diruthenium diphosphazane-bridged species [Ru2(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri)

Thermolysis of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2], [Ru2H2(CO)4{µ-(RO)2PN(Et)P(OR)2}2] or [Ru2{µ-OC(O)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) under appropriate reaction conditions affords the formally unsaturated species [Ru2(CO)4{µ-(RO)2PN(Et)P(OR)2}2], which have been established by X-ray crystallography for both R = Me and R = Pri to contain two complementary semi-bridging carbonyl groups as well as two terminal carbonyls. These compounds are highly labile and react under mild conditions with a range of small molecule nucleophiles and electrophiles including carbon monoxide, isonitriles, nitrosyl ions, alkynes, sulfur, hydrogen sulfide, dioxygen, sulfur dioxide, tin(II) chloride, dihydrogen, protons, halogens and carbon tetrachloride. The compound [Ru2H2(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2], the product of the reaction involving dihydrogen and the tetraisopropoxy-diphosphazane derivative and in which, as determined by X-ray crystallography, the hydrogens are situated equatorially and trans to each other on different ruthenium atoms, is also highly reactive, typically reductively eliminating dihydrogen in its reactions with nucleophiles including alkynes.