Electrophilic attack on diphosphazane-bridged derivatives of diruthenium nonacarbonyl by halogens. Crystal structure of [Ru2(µ-I)I(CO)3{µ-(PriO)2PN(Et)P(OPri)2}2]

Abstract

Treatment of [Ru₂(µ-CO)(CO)₄{µ-(RO)₂PN(Et)P(OR)₂}₂](R = Me or Prⁱ) with halogens results in the ready formation of [Ru₂X(CO)₅{µ-(RO)₂PN(Et)P(OR)₂}₂]⁺(X = Cl, Br or I) with the halogen atom co-ordinating terminally. These pentacarbonyl species, isolated as their hexafluorophosphate salts, decarbonylate in solution, rapidly in the presence of trimethylamine N-oxide dihydrate but slowly in the absence of this decarbonylating agent, to produce the tetracarbonyl species [Ru₂(µ-X)(CO)₄{µ-(RO)₂PN(Et)p(OR)₂}₂]⁺ in which the halogen bridges the two ruthenium atoms. Substitution of the carbonyl groups in these tetracarbonyl species can be effected further by halide ions, either photochemically or by promoting the process using Me₃NO·2H₂O and thus reaction of [Ru₂(µ-X)(CO)₄{µ-(RO)₂PN(Et)P(OR)₂}₂]⁺ with chloride, bromide or iodide ions in the presence of Me₃NO·2H₂O readily affords [Ru₂(µ-X)X(CO)₃{µ-(RO)₂PN(Et)P(OR)₂}₂]. Significantly, treatment of [Ru₂I(CO)₅{µ-(RO)₂PN(Et)P(OR)₂}₂]I₃, or [Ru₂I(CO)₅{µ-(RO)₂PN(Et)P(OR)₂}₂]PF₆ in the presence of iodide ions, with an excess of Me₃NO·2H₂O leads solely to the neutral tetracarbonyl derivative [Ru₂I₂(CO)₄{µ-(RO)₂PN(Et)P(OR)₂}₂]. On the basis of an X-ray crystallographic study on [Ru₂(µ-I)I(CO)₃{µ-(PrⁱO)₂PN(Et)P(OPrⁱ)₂}₂], the tricarbonyl derivatives have structures related to that of [Ru₂(µ-X)(CO)₄{µ-(RO)₂PN(Et)P(OR)₂}₂]⁺ with an axial carbonyl group having been replaced by a halide ion.