Cyclodextrins as first and second sphere ligands for Rh(I) complexes of lower-rim PTA derivatives for use as catalysts in aqueous phase hydrogenation

The rhodium complex [Rh(cod)Cl(N-tBuBzPTA)]PF6 (2) was obtained by reacting the appropriateRh(I) precursor with the lower-rim PTA derivative [N-tBuBzPTA]PF6 (tBuBz = 4-tert-butylbenzyl; PTA =1,3,5-triaza-7-phosphaadamantane). The solubility and stability in water of 2 were increased in the presenceof native-?-cyclodextrin (beta-CD). The interaction of 2 with mono-amino beta-cyclodextrin (beta-CDNH2, 2 equiv.)led to a supramolecular Rh assembly (3), identified by 31P, 1H and 2D T-ROESY NMR experiments. The catalyticactivity of 3 was evaluated in thewater-phase hydrogenation of unsaturated and allylic alcohols and preliminaryresults are presented here.