Diiron MU-vinyliminium complexes from acetylene insertion into a metal-aminocarbyne bond

The complexes [Fe-2{mu-CN(Me)(R)}(mu-CO)(CO)(NCMe)(CP)(2)] [SO3CF3] (R = Xyl, 1a; R = Me, 1b; R = CH2Ph, 1c; Xyl = 2,6-Me2C6H3 containing a labile NCMe ligand, react under mild conditions with a variety of terminal alkynes HCdropCR' (R' = SiMe3, Me, Bu-n, Tol, Ph, H; Tol = 4-MeC6H4) to give the bridging vinyliminium complexes [Fe-2{mu-sigma:eta(3)-CR')=CHC=N(Me)(R)}(mu-CO)(CO)(CP)(2)] [SO3CF3] (R = Xyl, 1A; R = SiMe3, 2a; R = Me, R' = SiMe3, 2b; R = CH2Ph, R-n = SiMe3, 2c; R = Xyl, R' = Me, 3a; R = R' = Me, 3b; R = Xyl, R' = Bu-n, 4; R = Xyl, R' = Tol, 5a; R = Me, R' = Tol, 5b; R = CH2Ph, R' = Tol, 5c; R = Xyl, R' = Ph, 6; R = Xyl, R' = H, 7). Insertion of the alkyne into the metal-carbyne carbon bond is regiospecific, resulting only in the product containing the R' group on the carbon bound to Fe. Similarly, insertion of the disubstituted alkynes R'Cequivalent toCR' (R' = Me, Et) affords the analogous compounds [Fe-2{mu-sigma:eta(3)-C(R')=C(R')C=N(Me)(R)(mu-CO)(CO)(CP)(2)] [SO3CF3] (R = Xyl, R' = Me, 8a; R = R'= Me, 8b; R = CH2Ph, R'= Me, 8c; R = Xyl, R'= Et, 9a; R = Me, R'= Et, 9b). The molecular structure of complex 2a has been elucidated by an X-ray diffraction study.