Syntheses and reactivities of azido coordinated CpCo(dithiolene) complexes

Abstract

Azido coordinated dithiolene complexes [CpCo(N 3){S 2C 2(CO 2Me) 2}( S-CHR 1R 2)], where R 1, R 2 = H ( 4a); R 1 = H, R 2 = SiMe 3 ( 4b); R 1 = H, R 2 = CO 2Et ( 4c), were synthesized by the reactions of the corresponding Cl − coordinated precursors [CpCo(Cl){S 2C 2(CO 2Me) 2}( S-CHR 1R 2)] ( 3a– 3c) with sodium azide. The Cl − coordinated complex 3d (R 1, R 2 = CO 2Me) did not produce any N 3 − coordinated complexes but formed the CR 1R 2-bridged alkylidene adduct [CpCo{S 2C 2(CO 2Me) 2}(CR 1R 2)] ( 2d; R 1, R 2 = CO 2Me). The structure of 4a was determined by X-ray diffraction study. In the molecular structure of 4a, the coordinated N 3 − ligand and CHR 1R 2 group were located at the same side with respect to the dithiolene ring ( syn form), although the corresponding Cl − precursor ( 3a; R 1, R 2 = H) was anti form. A structural conversion of syn/ anti was conceivable during the Cl −/N 3 − ligand exchange. Thermal (80 °C) and photochemical reactions (Hg lamp) of 4a– 4c were performed. Among them, 4c was relatively well reacted compared with the others to form the CR 1R 2-bridged alkylidene adduct ( 2c; R 1 = H, R 2 = CO 2Et), followed by a formal HN 3 elimination, and the reaction also produced non-adduct of the cobalt dithiolene complex [CpCo{S 2C 2(CO 2Me) 2}] ( 1). The electrochemical 1e − reduction of 4c underwent a formal N 3 − ligand elimination, and successive second reduction caused the CHR 1R 2 group elimination or reformed the CR 1R 2-bridged alkylidene adduct 2c.