Syntheses and reactivities of azido coordinated CpCo(dithiolene) complexes

Abstract Azido coordinated dithiolene complexes [CpCo(N 3 ){S 2 C 2 (CO 2 Me) 2 }( S -CHR 1 R 2 )], where R 1 , R 2  = H ( 4a ); R 1  = H, R 2  = SiMe 3 ( 4b ); R 1  = H, R 2  = CO 2 Et ( 4c ), were synthesized by the reactions of the corresponding Cl − coordinated precursors [CpCo(Cl){S 2 C 2 (CO 2 Me) 2 }( S -CHR 1 R 2 )] ( 3a – 3c ) with sodium azide. The Cl − coordinated complex 3d (R 1 , R 2  = CO 2 Me) did not produce any N 3 − coordinated complexes but formed the CR 1 R 2 -bridged alkylidene adduct [CpCo{S 2 C 2 (CO 2 Me) 2 }(CR 1 R 2 )] ( 2d ; R 1 , R 2  = CO 2 Me). The structure of 4a was determined by X-ray diffraction study. In the molecular structure of 4a , the coordinated N 3 − ligand and CHR 1 R 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 1 R 2 -bridged alkylidene adduct ( 2c ; R 1  = H, R 2  = CO 2 Et), followed by a formal HN 3 elimination, and the reaction also produced non-adduct of the cobalt dithiolene complex [CpCo{S 2 C 2 (CO 2 Me) 2 }] ( 1 ). The electrochemical 1e − reduction of 4c underwent a formal N 3 − ligand elimination, and successive second reduction caused the CHR 1 R 2 group elimination or reformed the CR 1 R 2 -bridged alkylidene adduct 2c .