Keep it simple: tailored functionalizations of a versatile phosphine for use in aqueous phase catalysis

One of the main obstacles to the widespread use of water soluble organometallic complexes in catalysis is the often cumbersome and scarcely selective synthesis of a library of suitable ligands, such as hydrosoluble phosphines. In the last few years we have studied the chemistry of the versatile amphiphilic cage aminophosphine PTA (1,3,5- triaza-7-phosphaadamantane) and obtained a library of derivatives based on its functionalization in 6-position (“upper rim”) and on N-alkylation (“lower rim”).1 Some of the former class of ligands were used to coordinate metal fragments such as {Ir(cod)}2 and {Ru(η6-arene)} moieties, and the corresponding complexes were used in catalytic hydrogenation of unsaturated substrates under mild conditions.3 In parallel, from the second class of ligands, N-benzylated PTA bromides were used in combination with Rh(I) precursors for the biphasic catalytic hydroformylation of higher olefins in the presence of randomly methylated β-cyclodextrin (RAME-β-CD).