Cluster chemistry. Part 32. Synthesis and X-ray crystal structure of [Ru5(µ5-η2-C2PPh2-P)(µ-PPh2)(CO)13], a complex containing an alkynyl ligand in extended interaction with an open Ru5 cluster

Abstract

The radical ion-initiated reaction between [Ru₃(CO)₁₂] and C₂(PPh₂)₂(dppa)(in 2 : 1 ratio) gives [{Ru₃(Co)₁₁}₂(µ-dppa)](2), in which the acetylenic bis-tertiary phosphine bridges two monosubstituted Ru₃ clusters. On heating (90 °C, 1 h), complex (2) is converted into [Ru₅(µ₅-η²-C₂PPh₂-P)(µ-PPh₂)(CO)₁₃](3) in 88% yield, which was characterised by an X-ray study at 295 K. The complex contains a seven-electron donor C₂PPh₂ ligand interacting with all five Ru atoms of an open Ru₅ cluster consisting of three edge-fused Ru₃ triangles (a ‘swallow’ cluster); the PPh₂ group bridges the non-fused edge of the central triangle. Some comparisons with [Ru₅(µ₅-CNBu^t)(CO)₁₄(CNBu^t)] and [Ru₅(µ₅-C₂Ph)(µ-PPh₂)(CO)₁₄] are made. Crystals of complex (3) are monoclinic, space group P2₁/n, with a= 17.00(1), b= 17.394(9), c= 14.260(7)Å, β= 92.89(4)°, and Z= 4; the structure was refined by least-squares methods to a residual of 0.031 for 6 364 independent ‘observed’ reflections.