Low temperature allene coupling and isomerization at triosmium clusters

Facile coupling and isomerization of allene (CH2CCH2) has been found on its interaction at low temperatures with [H2Os3(CO)10] to give the di-allyl species [Os3(μ3-η1:η2:η3-C6H8)(CO)10] (1) and [Os3(μ3-η1:η2:η3-C6H8)(CO)9] (2) in which two allene molecules are bonded in an end-to-centre array. Cluster 2 converts either in solution or in the solid state into two different species: the colourless derivative [Os3H(μ3-η1:η1:η1:η2-C6H7)(CO)9] (3) and the metallocyclopentadiene [Os3(μ-η1:η1:η2:η2-C6H8)(CO)9] (4), which could be regarded as the result of 1,3-hydrogen shifts of the coupled allene at triosmium clusters.