Cluster chemistry: LXXXIX. Oligomerization reactions of allene with Ru 5(μ 5-C 2PPh 2)(μ-PPh 2)(CO) 13

Abstract

Reactions between Ru 5(μ 5-C 2PPh 2)(μ-PPh 2)(CO) 13 ( 1) and allene have given two isomers of Ru 5(μ 4-C 2PPh 2)(μ-PPh 2)(μ-C 6H 8)(μ-C 3H 4)(CO) 10 ( 2, 3) containing the η 3: η 3-biallyl ligand, Ru 5(μ 4 -C 2PPh 2)(μ-PPh 2)(μ-C 9H 12)(μ-C 3H 4)(CO) 10 ( 7) containing an allene trimer, and Ru 5(μ 5-C 8H 8 PPh 2)(μ-PPh 2)(CO) 11 ( 8), in which an allene dimer has linked with the phosphinoacetylide ligand. Complex 2 reacted with P(OMe) 3 to give two isomers of Ru 5(μ 4-C 2-PPh 2)(μ-PPh 2)(μ-C 6H 8)(μ-C 3H 4)(CO) 9{P(OMe) 3} ( 4 and 5) both of which were shown to be structurally related to 2 and 3; a third isomer, 6, was obtained from similar reactions of 3 and P(OMe) 3. In complexes 2–6, the metal cores consist of wing-tip spiked planar rhombi, one RuRu separation of which is very long (3.19–3.38 Å); they contain μ-biallyl ligands formed by dimerization of two allene molecules. The metal core of 7 consists of a similar Ru 4 rhombus with the fifth Ru atom connected via the C 2PPh 2 and μ-C 9H 12 ligands. The latter is formed from three allene molecules and is coordinated to a cluster Ru atom by a 1,3-diene unit and to the separated Ru atom by an η 3-allyl unit. All three complexes also contain a μ-σ,η 3-C 3H 4 ligand. In 8, incorporation of the acetylide carbons into the Ru 4 rhombus has given a C 2Ru 4, octahedron, of which a wing-tip Ru is also attached to the fifth Ru atom. A PPh 2 group bridges this Ru atom and a carbon of the cluster C 2 unit; the second carbon is linked to the C 6H 8 moiety which is attached to the cluster by σ and η 4 interactions. The results of single crystal X-ray studies of complexes 3– 7 are reported.