Synthesis of a new family of water-soluble tertiary phosphine ligands and of their rhodium(I) complexes; olefin hydrogenation in aqueous and biphasic media

Abstract

The series of phosphonium phosphines [Ph 2P(CH 2) n PMe 3]X ( n = 2, 3, 6, 10; X = NO − 3, Cl −, PF − 6), henceforth II-, III-, VI-, and X-phosphos, respectively, have been prepared and characterized. The ligands react with [NBDRhCl] 2 (NBD = norbornadiene) to form the complexes [NBDRhCl(n-phosphos)]X, one of which, [NBDRhCl(II-phosphos)]PF 6, has been characterized crystallographically. The 1:1 complexes [NBDRhCl( n-phosphos)]X react with a second equivalent of ligand to form the complexes [NBDRh( n-phosphos) 2]X, which form very active olefin hydrogenation catalysts in aqueous and aqueous—organic biphasic systems. The effect of chain length on activity is very significant, the complex of VI-phosphos forming the most active catalyst.