Synthesis, redox properties, and X-ray diffraction structure of 2,3-bis(ethylthio)-N-(p-MeOC6H4)maleimide

Abstract

Refluxing 2,3-dichloromaleic anhydride with p-anisidine in benzene with water removal gives the condensation product 2,3-dichloro-N-(p-MeOC6H4)maleimide (1) 75% yield. This new maleimide compound reacts with added ethanethiol in the presence of Et3N or DBU to furnish the bidentate sulfide ligand 2,3-bis(ethylthio)-N-(p-MeOC6H4)maleimide (2) in 85% yield. Each product has been characterized in solution by IR, NMR, and UV-vis spectroscopies, and the solid-state structure of 2,3-bis(ethylthio)-N-(p-MeOC6H4)maleimide was unequivocally established by single-crystal X-ray diffraction analysis. 2,3-bis(Ethylthio)-N-(p-MeOC6H4)maleimide crystallizes in the monoclinic space group C2/c, a = 20.035(3)A, b = 9.188(1)A, c = 16.887(2)A, β = 93.696(2)°, V = 3102.3(8)A3, Z = 8, and Dcalcd = 1.385 mg/m3; R = 0.0268, Rw = 0.0676 for 2025 reflections with I > 2σ (I). The nature of the LUMO in 2,3-bis(ethylthio)-N-(p-MeOC6H4)maleimide (2) has been determined by extended Huckel molecular orbital calculations, and these data are discussed relative to the cyclic voltammetry results and other structurally relevant compounds prepared in our labs.