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 [Os-3(mu(3)-eta(1):eta(2):eta(3)-C6H8)(CO)(10)] (1) and [Os3(mu(3)-eta(1):eta(2):eta(3)-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(mu(3)-eta(1):eta(1):eta(1):eta(2)-C6H7)(CO)(9)] (3) and the metallocyclopentadiene [Os-3(mu-eta(1):eta(1):eta(2):eta(2)-C6H8)(CO)(9)] (4), which could be regarded as the result of 1,3-hydrogen shifts of the coupled allene at triosmium clusters.