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⁺.