Synthesis and structures of heterobimetallic Ir2M (M=Pd, Pt) sulfido clusters and their catalytic activity for regioselective addition of alcohols tointernal 1-aryl-1-alkynes

The heterobimetallic trinuclear sulfido clusters [(Cp*Ir)(2)(mu (3)-S)(2)MC l2] (M = Pd (3), Pt (4); Cp* = eta (5)-C5Me5) were synthesized from the din uclear hydrogensulfido complex [Cp*IrCl(mu -SH)(2)IrCp*Cl] (2) and [MCl2(CO D)] (COD = cycloocta-1,5-diene), while the reaction of 2 with [Pd(PPh3)(4)] afforded the cationic trinuclear cluster [(Cp*Ir)(2)(mu (3)-S)(2)PdCl(PPh3 )]Cl (5). Clusters 3 and 4 reacted with PPh3 to give a series of mono and d icationic clusters including 5, while the dicationic clusters [(Cp*Ir)(2)(m u (3)-S)(2)M(dppe)][BPh4](2) (M = Pd (9), Pt (10); dppe = Ph2PCH2CH2PPh2) w ere obtained by the reaction with dppe followed by anion metathesis. The mo lecular structures of 5 . CH2Cl2, 9 . CH3COCH3, and 10 . CH3COCH3 were dete rmined by X-ray crystallography. Clusters 3 and 4 were found to catalyze th e addition of alcohols to alkynes to give the corresponding acetals. Intern al 1-aryl-1-alkynes were transformed by cluster 3 into the corresponding 2, 2-dialkoxy-1-arylalkanes with high regioselectivity up to 99:1, while clust er 4 was a much less regioselective catalyst. (C) 2001 Elsevier Science B.V . All rights reserved.