Activation of C=N bonds by high-valent group 6 metal chlorides, including the conversion of an -diimine into a functionalized imidazolium

摘要

The -diimine (Xyl)N?CHCH?N(Xyl) (DAD(Me); Xyl = 2,6-C6H3Me2) was converted by the reaction with WCl6 into the iminomethyl-imidazolium compound [(Xyl)NCH?CHN(Xyl)CCH?N(Xyl)][WCl6], 1, in 47% yield. Mono (N-protonated) -diimine salts were isolated from the reactions of WCl6 with (2,6-C6H3Et2)N?C(Me)C(Me)?N(2,6-C6H3Et2) (Me-DAD(Et)) and of MoCl5 with (2,6-C6H3Et2)N?CHCH?N(2,6-C6H3Et2) (DAD(Et)) and (2,6-(C6H3Bu2)-Bu-t)N?CHCH?N(2,6-(C6H3Bu2)-Bu-t) (DAD(tBu)), giving respectively [(2,6-C6H3Et2)NH?CHCH?N(C6H2Et2Me)][WCl6], 2 (minor product), [DAD(Et)(H)](2)[Mo2Cl10], 3a, and [DAD(tBu)(H)](2)[Mo2Cl10], 3b. MoCl5 reacted with the carbodiimide (4-C6H4Me)N?C?N(4-C6H4Me) affording 70% yield of MoCl4[(4-C6H4Me)NC(Cl)N(4-C6H4Me)], 4. All the products were characterized by analytical and spectroscopic methods, and the X-ray structures of 1, 2 and 4 were elucidated by X-ray diffraction. DFT calculations were performed to shed light on mechanistic and structural aspects.