Synthesis, crystal structure and electrospray mass spectrometric study of the rhodium(III) dioxolene complex [Rh{OCC(CO2Et)SC(CO2Et)CO}(η5-C5Me5)(PPh3)]
Abstract
Reaction of the complexes [RhCl2(η5-C5Me5)L][L = PPh3, pyridine (py) or P(OPh)3] with the cyclic diketones [graphic omitted]H(CO2Et)(X = O or S) and excess silver(I) oxide yields the cyclic rhodium(III) dioxolene complexes [Rh{O[graphic omitted]O}(η5-C5Me5)L]. The complexes have been fully characterised by elemental analysis, and IR and NMR spectroscopies. A single-crystal X-ray diffraction study on [Rh{O[graphic omitted]O}(η5-C5Me5)(PPh3)] reveals the expected pianostool co-ordination about the rhodium centre, which is tipped out of the otherwise almost planar dioxolene system. Electrospray mass spectrometry has been used to probe the co-ordination chemistry, specifically demonstrating that the triphenylphosphine ligand is labile, and can be trapped by such reagents as H2O2, S8, Se and AgNO3. The resulting Ph3PE (E = O, S or Se) ligands show differing tendencies to co-ordinate to the resulting Rh centre. With Mel, the dioxolene ligand is cleaved, via alkylated intermediates, and the species [Rhl(C5Me5)(NCMe)]+ and [Rhl(C5Me5)(PPh3)]+ are detected in the resulting reaction mixture, together with PPh3Me+.