Novel coordination modes of partially hydrogenated diyne ligands on metal carbonyl clusters

The reaction of [Ru4H4(CO)(12)] with the 1,3-diynes RC2C2R (R=Me, SiMe3 or Ph) under reflux conditions, in heptane, yielded the tetraruthenium cluster s [Ru-4(CO)(12){mu (4)-eta (1):eta (2):eta (2):eta (1)-(RCH2C3R)}] 1 and [R u-4(CO)(12){mu (4)-eta (2):eta (1):eta (1):eta (2)-[RC(H)C](2)}] 2 (R=Me a, SiMe3 b or Ph c) in good yield. In 1 a 1,1-dihydrogenation occurs to gener ate an allene-1,3-diyl ligand, which coordinates to the butterfly Ru-4 face in a novel eta (1):eta (2):eta (2):eta (1) mode, whereas in 2 a 1,4-dihydr ogenation occurs to yield a 1,3-diene-2,3-diyl ligand bound to the Ru-4 but terfly via four C atoms in a eta (2):eta (1):eta (1):eta (2) mode. In addit ion, the trinuclear cluster [Ru-3(mu -H)(CO)(9){mu (3)-eta (2):eta (2):eta (1)-[RCH2C2CHPh)] 3c (R=Ph) is produced as a result of 1,1,4 trihydrogenati on of the diyne and loss of one ruthenium vertex. The clusters have fully b een characterised spectroscopically, and the crystal structures of 1a,1c 2a ,2c and 3c determined.