Cyclohexa- and cycloheptadienyl complexes of the group 6 metals

The syntheses of a range of cyclohexadienyl- and cycloheptadienylchromium complexes are presented. Addition of nucleophiles to [(eta-C6H6)Cr(CO)(3)] and [(eta(6)-C7H8)Cr(CO)(3)] followed by treatment with N-methyl-N-nitroso-p-toluenesulfonamide (Diazald) gave [(eta(5)-C(6)H(6)R)Cr-(CO)(2)(NO)] (3a, R = H; 3b, R = C(Me)S(CH2)(3)S; 3c, R = CHPh(2)) and [(eta(5)-C(7)H(8)R)Cr(CO)(2)-(NO)] (9b, R = C(Me)S(CH2)(3)S; 9c, R = CHPh(2)), respectively. Reaction of 3b with phenyllithium followed by treatment with electrophiles [R'O-3](+) (R' = Me, Et) gave the carbene complexes [(eta(5)-C(6)H(6)R)(CO)(NO)Cr=C(OR')Ph] (5a,b). Abstraction of hydride from 3a and 9a (R = H) gave the highly sensitive cations [(eta-C6H6)Cr(CO)(3)(NO)](+) (6) and [(eta(6)-C7H8)Cr-(CO)(2)(NO)](+) (11), respectively. The preparation of the triarylstannyl complexes [(eta(5)-C(7)H(8)R)M(CO)(3)(SnPh(3))] (10a, M = Cr, R = C(Me)S(CH2)(3)S; 10b, M = Cr, R = CHPh(2); 10c, M = W, R = H) is presented. The X-ray crystal structure of [eta(5)-C7H9)W(CO)(3)(SnPh(3))]bullet>0.5CH(2)Cl(2) (10c) is reported and shows two different rotamers of 10c as well as a single molecule of CH2Cl2 in the asymmetric unit.