Synthesis and molecular structure of cisoid and transoid isomers of [Re2(CO)6(1,1′-bis(indenylidene)] derived from the reaction of [Re2(CO)8(MeCN)2] and diazoindene

The compound [Re₂(CO)₈(MeCN)₂] reacts with diazoindene (C₉H₆N₂) while refluxing in THF to afford three dirhenium products in which C₉H₆N₂ is cleaved with loss of N₂ and with incorporation of the residual indenylidene group into the products. Two indenylidene groups are coupled in two diastereomers of [Re₂(CO)₆(μ,η⁵:η⁵-1,1′-C₁₈H₁₂)] where C₁₈H₁₂=bis(indenylidene). X-ray structures show that these isomers are related as RR/SS and RS isomers. These have the two Re(CO)₃ groups coordinated transoid and cisoid, respectively to a trans bis(indenylidene) bridge. The third product is the μ-indenylidene complex [Re₂(CO)₈(μ,η¹:η⁵-C₉H₆)], which was also structurally characterised by X-ray diffraction.