Tetra-hydroxy-calix[4]arene derivatives with two P(III) or P(V) units attached at the upper rim

Abstract

5,17-Bis(diphenylphosphino)-25,26,27,28-tetra-hydroxy-calix[4]arene (2) and the corresponding bis-(phosphine oxide) (3) and bis-(phosphine sulfide) (4) have been synthesized. A single crystal X-ray diffraction study was carried out for bis(phosphine oxide) 3, which revealed a pinched cone conformation for the calixarene core. In the solid state, each calixarene is linked to two other calixarenes via hydrogen bonds involving the phosphoryl groups as well as two of the four hydroxyl groups, thereby generating a supramolecular polymeric structure. Selective formation of chelate complexes from diphosphine 2 failed, probably because of rapid trans annular rotation of the phenoxyl groups that prevents appropriate ligand preorganisation. Upon reaction with appropriate Ru-, Rh-, and Ir-complexes, ligand 2 readily formed dinuclear complexes. One of them, namely the complex [2·{RhCl(1,5-cyclooctadiene)}2] was assessed in the catalytic hydrogenation of linear and cyclic olefins.