Reaction of Pyrones with Triosmium Clusters

Reaction of Os 3 (CO) 10 (NCCH 3 ) 2, 2, with coumarin, chromone, α-pyrone, γ-pyrone, or 2-methyl-3-hydroxy-γ-pyrone afforded the products Os 3 (CO) 10 (μ-H)(μ-L), 3, in which the pyrone is anchored onto the triosmium framework via the exocyclic oxygen and orthometalation; the major product for the last pyrone is Os 3 (CO) 9 (μ-H)(μ-γ-C 6 H 5 O 3 ), 5, coordinated via the hydroxyl group rather than an orthometalation. The cluster Os 3 (CO) 10 (μ-H)(μ-OH), 7, formed H-bonded adducts, 8, with unsubstituted pyrones; the OH functioned as the H-donor.