Synthesis of Hybrid Ligands with Nitrile and Cage Phosphane Donor Groups and their Applications in Gold-Mediated Reactions
Abstract
Altering the donor properties of phosphane ligands through substituent variation is an established tool in coordination chemistry and catalysis. This contribution describes the synthesis of two new hybrid donors (L) combining 1,3,5,7-tetramethyl-2,4,6-trioxa-8-phosphaadamantane-8-yl (PCg) and nitrile donor groups at different molecular scaffolds, viz. ferrocene-1,1'-diyl (fc) and 1,2-phenylene.
These ligands were used to prepare dimeric Au(I) complexes [Au(2)(μ(P,N)-L)(2)][SbF6](2), which were evaluated as silver-free, preformed catalysts in Au-mediated cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol to 2,3-dimethylfuran. The catalyst featuring the ferrocene-based ligand, viz., [Au(2)(μ(P,N)-CgPfcCN)(2)][SbF6](2), showed the best catalytic performance at low catalyst loading (0.5 or 0.15 mol.%), which exceeded that of its diphenylphosphanyl analog [Au(2)(μ(P,N)-Ph(2)PfcCN)(2)][SbF6](2) studied earlier and the prototypical Au(I) precatalyst [Au(PPh3)(MeCN)][SbF6].