Reactions of co-ordinated ligands. Part 26. The reaction of ethylene and acetylene with tri-µ-carbonyl-tris(η5-indenyl)-triangulo-trirhodium; the formation and molecular structure of the bridged vinylalkylidene complex [Rh2(µ-CCH2)(CO)2(η5-C9H7)2], and its protolysis to form a bridged cationic vinyl complex
- 1 January 1982
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 2,p. 319-326
- https://doi.org/10.1039/dt9820000319
Abstract
The complex [Rh(CO)2(η5-C9H7)] decarbonylates in refluxing heptane to form [Rh3(µ-CO)3(η5-C9H7)3]. Reaction of the Rh3 cluster with ethylene affords a high yield of [Rh(CO)(C2H4)(η5-C9H7)], which reforms the Rh3 cluster in solution. Treatment (60 °C. toluene) of [Rh(CO)(C2H4)(η5-C9H7)] with acetylene affords as the major product the bridged vinylalkylidene complex [Rh2(µ-CCH2)(CO)2(η5-C9H7)2]. An X-ray crystallographic study has been carried out on this complex. Crystals are monoclinic, space group P21/c, Z= 4, in a unit cell of dimensions a= 13.482(3), b= 9.568(3), c= 14.801(6)Å, and β= 100.69(3)°. The structure has been refined to R 0.021 (R′ 0.021) for 2 999 unique reflections to 2θ⩽ 50°(Mo-Kα, X-radiation). The µ-CCH2 group symmetrically bridges two Rh(CO)(η5-C9H7) fragments linked by a Rh–Rh bond [Rh(1)–Rh(2)2.691 (1)Å]. A minor product in this reaction is obtained in higher yield by treating acetylene with [Rh3(µ-CO)3(η5-C9H7)3, and is characterised as a complex containing two Rh(η5-C9H7) units linked by a µ-pentadien-3-one fragment. Reaction of this complex with carbon monoxide or heating affords the cyclopentadienone complex, [Rh(η4-C4H4CO)(η5-C9H7)]. Reaction of [Rh2(µ-CCH2)(CO)2(η5-C9H7)2] with HBF4–Et2O gives [Rh2(µ-CHCH2)(µ-CO)(CO)(η5-C9H7)2][BF4], there being no evidence for the formation of a bridged alkylidyne complex.Keywords
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