Coordination Chemistry of Cyclopentadienyl Ester-Disubstituted Ligands. Synthesis and Solid State Structures of [Na([18]-crown-6)][C5H3(CO2Et)2-1,2] and [Mn{C5H3(CO2Ph)2-1,2}(CO)3]

The disubstituted alkyl- and aryloxycarbonylcyclopentadienides of sodium Na[C5H3(CO2R)2-1,2] [R = Me (3a), Et (3b), Ph (3c)] are obtained in a two-step synthesis. The known Na[C5H4(CO2R)] [R = Me (1a), Et (2b)] and the hitherto unknown Na[C5H4(CO2Ph)] (1c), prepared from NaCp and dialkyl- or diphenyl carbonate, are subsequently reacted with the corresponding chloroformates ROCOCl to give 3 contamined with variable amounts of 1,3 isomers. Treatment of 3b with [18]-crown-6 affords the buff-colored crystalline salt [Na([18]-crown-6)][C5H3(CO2Et)2-1,2] (4b). Reactions of 4b and 3c with MBr(CO)5 [M = Mn, Re] or [RuCl2(CO)3]2 lead to the respective metal complexes [M{η5-C5H3(CO2R)2-1,2}(CO)3] [R = Et and M = Mn (5b) or Re (6b), R = Ph and M = Mn (5c)] and [Ru{C5H3(CO2Et)2-1,2}(CO)]2 (7b). The solid state structure of 4b reveals ion pairs in which the anion adopts an idealized C 2 v conformation and chelates the sodium (κ2 O,O‘-coordination). The structure of [Mn{C5H3(CO2Ph)2-1,2}(CO)3] (5c) confirms the expected η5-coordination of the Cp ring and exhibits significant torsion angles between the Cp ring and carboxylate groups.