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

The α-diimine (Xyl)N[double bond, length as m-dash]CHCH[double bond, length as m-dash]N(Xyl) (DADMe; Xyl = 2,6-C6H3Me2) was converted by the reaction with WCl6 into the iminomethyl-imidazolium compound [(Xyl)NCH[double bond, length as m-dash]CHN(Xyl)CCH[double bond, length as m-dash]N(Xyl)][WCl6], 1, in 47% yield. Mono (N-protonated) α-diimine salts were isolated from the reactions of WCl6 with (2,6-C6H3Et2)N[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]N(2,6-C6H3Et2) (Me-DADEt) and of MoCl5 with (2,6-C6H3Et2)N[double bond, length as m-dash]CHCH[double bond, length as m-dash]N(2,6-C6H3Et2) (DADEt) and (2,6-C6H3tBu2)N[double bond, length as m-dash]CHCH[double bond, length as m-dash]N(2,6-C6H3tBu2) (DADtBu), giving respectively [(2,6-C6H3Et2)NH[double bond, length as m-dash]CHCH[double bond, length as m-dash]N(C6H2Et2Me)][WCl6], 2 (minor product), [DADEt(H)]2[Mo2Cl10], 3a, and [DADtBu(H)]2[Mo2Cl10], 3b. MoCl5 reacted with the carbodiimide (4-C6H4Me)N[double bond, length as m-dash]C[double bond, length as m-dash]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.