Mono and diphosphine borane complexes grafted on polypyrrole matrix: Direct use as supported ligands for Rh and Pd catalysis

Article abstract of DOI:10.1016/S0022-328X(98)00684-6

A new versatile method for the synthesis of supported mono and diphosphines on polypyrrole matrix is described, based on the protective borane complexation of the phosphorus atom. For the first time, the unknown alkylation of a diphosphine ethano bridge, was obtained with near yield close to 70%, leading to its derivative 8 bearing the polymerizable pyrrole group on a side chain. The different supported mono and diphosphine boranes 12-15 have been applied with success in palladium-catalyzed allylation, cross-coupling reaction and in rhodium-catalyzed hydrogenation. It is of particular interest that supported phosphine boranes can be used without previous decomplexation, forming in situ the catalytically active species from Pd(OAc)₂ or RhCl₃. Moreover, the recoverable polymer could be used again in rhodium-catalyzed hydrogenation with a very good efficiency after several turn-overs. Nethertheless, we may point out that with palladium catalysis, the addition of Pd(dba)₂ was necessary to recover the catalytic activity. These results demonstrate that the phosphine borane complexes are key precursors for the synthesis of functionalized mono and diphosphines, and for their direct use in generating catalysts.