The cluster/surface analogy: the binding of norbornene on a triangulated array of metals

Abstract

Reactions of [Os₃(CO)₁₀(NCMe)₂] 1 with norbornene (bicyclo[2.2.1]hept-2-ene, nbe) led to two isomeric triosmium clusters [Os₃(μ-H)(CO)₁₀(μ-η¹∶η²-C₇H₉)] 2 and 3 and also the dihydride species [Os₃(μ-H)₂(CO)₉(μ₃-η¹∶η²∶η¹-C₇H₈)] 4. The molecular structure of compound 4 established by single crystal X-ray analysis shows norbornene–metal interactions similar to the proposed adsorption mode of norbornene found on the Pt(111) surface. The two isomers 2 and 3 exhibit an intermediate bonding mode between the solely π bound ligand and the di-σ,π bonding mode exhibited by cluster 4. These isomers differ in the orientation of the C₇H₈ moiety with respect to the triosmium triangle. Both 2 and 3 may exist in other isomeric forms which differ in the location of the hydride ligand. Compound 2 converts into 3 which on heating undergoes C–H bond cleavage to produce 4.