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

Abstract

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 clusters [Ru₄(CO)₁₂{μ₄-η¹∶η²∶η²∶η¹-(RCH₂C₃R)}] 1 and [Ru₄(CO)₁₂{μ₄-η²∶η¹∶η¹∶η²-[RC(H)C]₂}] 2 (R = Me a, SiMe₃b or Ph c) in good yield. In 1 a 1,1-dihydrogenation occurs to generate an allene-1,3-diyl ligand, which coordinates to the butterfly Ru₄ face in a novel η¹∶η²∶η²∶η¹ mode, whereas in 2 a 1,4-dihydrogenation occurs to yield a 1,3-diene-2,3-diyl ligand bound to the Ru₄ butterfly via four C atoms in a η²∶η¹∶η¹∶η² mode. In addition, the trinuclear cluster [Ru₃(μ-H)(CO)₉{μ₃-η²∶η²∶η¹-[RCH₂C₂CHPh)] 3c (R = Ph) is produced as a result of 1,1,4 trihydrogenation of the diyne and loss of one ruthenium vertex. The clusters have fully been characterised spectroscopically, and the crystal structures of 1a,1c 2a,2c and 3c determined.