Synthesis and reactivity of rhodium(I) complexes containing keto-functionalised N-pyrrolyl phosphine ligands

The reaction of [Rh(mu-Cl)(CO)(2)](2) with two equivalents of L [L = PR2{NC4H3C(O) Me-2}; R = Ph, L-1; R = NC4H4, L-2] gave the P,O-chelate complexes [RhCl(CO)(L-kappa(2)P,O)] (1, L = L-1; 2, L = L-2), whereas reaction with four equivalents of L gave [RhCl(CO)(L)(2)] (3, L = L-1; 4, L = L-2). Complexes 3 and 4 are fluxional in solution, and at low temperatures exist predominantly with one of the two keto groups coordinated. Complexes 3 and 4 undergo metal-promoted hydrolysis reactions with adventitious water leading to the diphosphoxane-bridged dimers [RhCl(CO)(mu-PR2OPR2)](2) (5, R = Ph; 6, R = NC4H4), with the carbonyl and chloride ligands both terminal and semi-bridging in 5 but solely terminal in 6. Complexes 3 and 4 react with NH4PF6 or TlPF6 to give cis-[Rh(L-kappa(2)P,O)(2)] PF6 (7b, L = L-1; 8, L = L-2). These complexes are also formed from the reaction of L with [Rh(mu-Cl)(cod)](2) in the presence of NH4PF6. Complex 8 reacts with CO to give [Rh(CO)(L-2)(2)] PF6 9, with PMe3 to give [Rh(PMe3)(2)(L-2-kappa(2)P, O)] PF6 10, and with [NEt(3)Bz] Cl (Bz = CH2Ph) to give [RhCl(L-2-kappa(1)P)(L-2-kappa(2)P, O)] 11. Complexes 2, 5 . CH2Cl2, 6 . C7H8, 7b, 8 and 11 have been crystallographically characterised. The electron-withdrawing character of L-1 and L-2 has led to differences in reactivity from the beta-ketophosphine PPh2CH2C(O) Ph and the ether-phosphine PPh2CH2CH2OMe.