Synthesis and structures of heterobimetallic Ir 2M (MPd, Pt) sulfido clusters and their catalytic activity for regioselective addition of alcohols to internal 1-aryl-1-alkynes

Abstract

The heterobimetallic trinuclear sulfido clusters [(Cp*Ir) 2(μ 3-S) 2MCl 2] (M=Pd ( 3), Pt ( 4); Cp*=η 5-C 5Me 5) were synthesized from the dinuclear hydrogensulfido complex [Cp*IrCl(μ-SH) 2IrCp*Cl] ( 2) and [MCl 2(COD)] (COD=cycloocta-1,5-diene), while the reaction of 2 with [Pd(PPh 3) 4] afforded the cationic trinuclear cluster [(Cp*Ir) 2(μ 3-S) 2PdCl(PPh 3)]Cl ( 5). Clusters 3 and 4 reacted with PPh 3 to give a series of mono and dicationic clusters including 5, while the dicationic clusters [(Cp*Ir) 2(μ 3-S) 2M(dppe)][BPh 4] 2 (M=Pd ( 9), Pt ( 10); dppe=Ph 2PCH 2CH 2PPh 2) were obtained by the reaction with dppe followed by anion metathesis. The molecular structures of 5·CH 2Cl 2, 9·CH 3COCH 3, and 10·CH 3COCH 3 were determined by X-ray crystallography. Clusters 3 and 4 were found to catalyze the addition of alcohols to alkynes to give the corresponding acetals. Internal 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 cluster 4 was a much less regioselective catalyst.