[5,5]-Fused Anhydride, Thioanhydride, and Imide Derivatives of Cyclopentadienyl Complexes: Electronic Effects of Mn(CO)3 and Ru(Cp*) Fragments

A new approach to 5,5-fused heterocyclic derivatives of cyclopentadienylmanganese tricarbonyl and pentamethylruthenocene is presented. 1,2-Dicarbophenoxycyclopentadienyl complexes of manganese and ruthenium were hydrolyzed to 1,2-dicarboxylic acids. Oxalyl chloride converted the acids to chlorocarbonyls, which reacted with bis(trimethylsilyl)sulfide to give the cyclopentadienyl-fused thioanhydrides. Alternatively, dehydration of the diacids with trifluoroacetic anhydride closed the diacids to cyclopentadienyl-fused anhydrides. Treatment of the anhydrides with p-toluidine followed by oxalyl chloride led to cyclopentadienyl-fused carboxylic imides. This approach enables direct comparison of electron-deficient Mn(CO)3 and electron-rich Ru(Cp*) coordination environments on the 5,5-fused heterocycles. Spectroscopic data reveal systematic downfield NMR shifts and higher infrared carbonyl stretching frequencies for the manganese complexes, consistent with lower electron density in the Mn(CO)3 compared to Ru(Cp*). Crystallographic analyses confirm that heterocycle fusion occurs without significant perturbation of the metal–cyclopentadienyl geometry. Comparative analysis across the series demonstrates that metal-dependent effects are primarily electronic rather than structural, with the Mn(CO)3 and Ru(Cp*) fragments modulating electron distribution within the fused ligand framework.