SYNTHESIS, CRYSTAL-STRUCTURES AND REACTIVITY OF RHODIUM(III) COMPLEXES CONTAINING BETA-KETOPHOSPHINE AND PHOSPHINO ENOLATE LIGANDS

The reaction of 3 equivalents of the ketophosphine Ph(2)PCH(2)C(O)Ph (L) with RhCl3 . 3H(2)O in ethanol yielded [RhCl3{Ph(2)PCH(2)C(O)Ph}{Ph(2)PCH(2)C(O)Ph}] in the form of the mer,trans-(1) and mer,cis-(2) isomers. Complex 2 exhibits fluxional behaviour on the H-1 NMR time-scale as a result of dynamic exchange between the pendant and the co-ordinated keto functions, the activation energy for this process being 75 +/- 2 kJ mel(-1). Treatment of 2 with TIPF6 in CH2Cl2 afforded the cationic complex trans,cis,cis- [RhCl2{Ph(2)PCH(2)C(O)Ph}(2)]PF6 3, which reacts with, excess L to give mer,cis-[RhCl{Ph(2)PCH - C(- O) Ph}{Ph(2)PCH(2)C(O)Ph}{Ph(2)PCH(2)C(O)Ph}]PF6 5. Complex 5 has an unprecedented ligand set: two ligands L, bound in two different co-ordination modes (terminal through P and chelating), and the corresponding phosphino enolate as the other chelate. In solution. fluxional behaviour is observed by P-31 NMR spectroscopy with an activation energy of 56 +/- 1 kJ mol(-1). The reaction of 3 with NaH afforded [{Rh(mu-Cl) [Ph(2)PCH - C(- O) Ph](2)}(2)] 6. The chloride bridges are readily cleaved by PMePh(2), affording [RhCl{Ph(2)PCH - C(- O) Ph}(2)(PMePh(2))] 7. Treatment of [RhCl(PPh(3))(3)] with 3 equivalents of L in toluene afforded the Rh-III complex mer.cis-[RhCl{Ph(2)PCH - C(- O) Ph}(2){Ph(2)PCH(2)C(O)Ph)] 8. Complex 2 and L reacted with NaOMe to afford the tris(enolato) Rh-III complex fac-[Rh(Ph(2)PCH - C(- O)Ph}(3)] 9. which could be also obtained from [RhCl(PPh(3))(3)]. The solid-state structures of 3 . CH2Cl2, 5 and 8 . CH2Cl2 have been determined by single crystal X-ray analysis.