VIII-B Coordination Chemistry of Sterically Hindered Ligands and Multidentate Ligands, and Activation of Small Molecules

Thiolate complexes continue to attract considerable attention due to their unique chemical properties and structural diversity. Since thiolate groups meet the electronic and steric requirements necessary to stabilize a wide variety of metal complexes, they have been used as auxiliary ligands. On the other hand, thiolate complexes are known to undergo chemistry at the sulfur center, including oxidation/reduction and protonation/ deprotonation, a complement to traditional chemistry for these complexes centered on the metal. In this study, we report the synthesis of a mononuclear vanadium(III) complex having the [SC6H3-2,6-(SiMe3)2] (= [SAr]–) ligands. The tris(arylthiolate) vanadium(III) complex (1) has been synthesized in good yield. This complex is found to undergo CH activation across a V–S bond in the presence of TMEDA to give a cyclometalated species along with free arylthiol. Complex 1 behaves as a twoelectron reductant toward Ad-N3, yielding an imide complex. Treatment of 1 with azobenzene produces an imide-sulfenamide compound, in which an azo N=N bond cleavage takes place concomitant with formation of a V=N and an S–N bond. These results suggests that the reaction proceeds through a cooperative activation sequence involving both vanadium and sulfur centers. Figure 1.