PREPARATION, STRUCTURE AND PROPERTIES OF TRIPHENYLPHOSPHINE RHODIUM ARYLOXIDES

The reaction of Wilkinson's catalyst with NaOAr in toluene cleanly aff ords the corresponding aryloxide complexes Rh(PPh3)(3)OAr (1), In solu tion, 1. exists in equilibrium with PPh3 and the corresponding Rh(PPh3 )(2)(pi-ArO) (2). The addition of HOAr shifts the equilibrium complete ly toward the corresponding adducts 2.2HOAr, due to hydrogen bonding b etween the oxygen atom of the pi-coordinated OAr ligand and two molecu les of HOAr. Heating of 1a-d in toluene at 60-80 degrees C leads to th e elimination ui HOAr with concomitant cyclometallation uf a phenyl ri ng of one PPh3 ligand, affording mixtures of 1, 2.2HOAr, a cyclometall ated Rh complex and PPh3. At room temperature, a reverse reaction slow ly occurs to give equilibrium mixtures of 1, 2 and PPh3. Complexes 1 r eadily react with water, CO and H-2, affording Rh-2(PPh3)(4)( mu-OH)(2 ),Rh(PPh3)(2)(CO)OAr (3) and HRh(PPh3)(3), respectively. The latter co mplex was also obtained when complexes 1 were treated with methanol. T he structures of the phenoxide complexes 1 and 2.2PhOH and of p-nitrop henoxide complex 3 were established by X-ray diffraction. (C) 1998 Els evier Science S.A. All rights reserved.