Cluster chemistry. Part 91. Clusters derived from 1,4-Bis (diphenylphosphino)buta-1,3-diyne and their pyrolysis products: a route to complexes containing the tetracarbon ligand

Abstract

Reactions of [M_n(CO)₁₁(NCMe)][M_n= Ru₃, Os₃, Re₃(µ-H)₃, or Ru₄(µ-H₄)₄] with the linear bis(phosphine) PPh₂C₂C₂PPh₂(bdpp) afford the ‘barbell’ complexes [{M_n(CO)₁₁}₂(µ-bdpp)][M_n= Ru₃1(38), Os₃2(68), Re₃(µ-H)₃4(44), or Ru₄6(39%)]. The monosubstituted complexes [M_n(CO)₁₁(bdpp)][M_n= Os₃3 or Re₃(µ-H)₃5] were isolated when an excess of bdpp was used. Reactions of 3 with [M₃(CO)₁₁(NCMe)][M₃= Ru₃ or Re₃(µ-H)₃] afforded the mixed-metal complexes [{Os₃(CO)₁₁}(µ-bdpp){M₃(CO)₁₁}][M₃= Ru 7(40) or Re₃(µ-H)₃8(63%)]. In a similar fashion [{Re₃(µ-H)₃(CO)₁₁}(µ-bdpp){Ru₃(CO)₁₁}]9 was prepared (38%) from 5 and [Ru₃(CO)₁₁(NCMe)]. When a solution of 1 in CH₂Cl₂ was gently heated under a nitrogen purge the C₄ complex [{Ru₃(µ-PPh₂)(CO)₉}₂(µ₃:µ₃-C₄)]10 was produced in 73% yield. Without purging, the yield is much reduced; a minor product from the reaction is [{Ru₄(µ-H)(CO)₁₂}{µ₄-PPh(C₆ H₄)C₂C₂PPh₂}{Ru₃(CO)₁₁}]. 11. Complex 11 contains an Ru₃(CO)₁₁ moiety linked via a PPh₂C₂C₂PPh(C₆H₄) ligand to an Ru-spiked Ru₃ cluster. One of the C₂ units is attached in a µ-σ,σ,η²-vinylic mode to the spike Ru and to two of the three Ru atoms in the closed triangular core. When 11 was recrystallised from CH₂Cl₂–MeOH the complex [{Ru₄(µ₃-OMe)(µ-PPh₂)(CO)₁₀}(µ₄-CCH-µ-η²-C ₂){Ru₂(µ-PPh₂)(CO)₆}]12 was formed. This complex contains an Ru₄ rhombus, opposite faces of which carry µ₃-OMe and a µ₄-vinylidene ligand; the latter is attached via a C–C single bond to the binuclear fragment. The complex [{Os₃(µ-PPh₂)(CO)₉}₂(µ₃:µ₃-C₄)]13 was obtained (78%) by pyrolysis of 2 in refluxing toluene. The structures of complexes 6 and 10–13 were determined by single-crystal X-ray studies.