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, L2] gave the P,Ochelate complexes [RhCl(CO)(L-(kappa)2P,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)2P,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)(L2)2]PF69, with PMe3 to give [Rh(PMe3)2(L^2-(kappa)2P,O)]PF610, and with [NEt3Bz]Cl (Bz = CH2Ph) to give [RhCl(L^2-(kappa)1P)(L^2-(kappa)2P,O)]11. Complexes 2, 5·CH2Cl2, 6·C7H8, 7b, 8 and 11 have been crystallographically characterised. The electron-withdrawing character of L1 and L2 has led to differences in reactivity from the (beta) -ketophosphine PPh2CH2C(O)Ph and the ether-phosphine PPh2CH2CH2OMe.