C,H bond activation of imino substituted heterocycles: Synthesis and crystal structure of [mu(2)-eta(3)-(R)N-CH2-C=C-C(H)=C(H)-X]Fe-2(CO)(6) and the isomeric clusters [mu(2)-eta(3)-(R)N-CH2-C=C-X-C(R')=C(R'')]Fe-2(CO)(6)

The reaction of Fe-2(CO)(9) with heterocyclic imines derived from thiophene 2-carbaldehyde or N-methyl-pyrrole-2-carbaldehyde produces the dinuclear compounds [mu(2)-eta(3)-(R)N-CH2-C=C-C(H)-X(H)-X]Fe-2(CO)(6) (R=Ph, C6H11, p-Bu-t-C6H4; X=S, NMe). The analogous reaction with imines of thiophene-3-carbaldehyde or indole-3-carbaldehyde yields the corresponding isomeric clusters [mu(2)-eta(3)-(R)N-CH2-C=C-X-C(R')=C(R '')]Fe-2(CO)(6) (R=Ph, C6H11, R'=R ''=H, X=S: R=Ph, p-Bu-t-C6H4, R'=R ''=-C6H4-, X=NH). The reaction proceeds via activation of the C,H bond in beta-position relative to the exocyclic C,N double bond of the imine ligands. A 1,3 hydrogen shift reaction then leads to the formation of a methylene group instead of the former imine carbon atom. So, the imine ligands are transformed into mu(2)-eta(3)-enyl-amido ligands being coordinated to an Fe-2(CO)(6) moiety, which is confirmed by X-ray structure analyses of six compounds.