C–S and C–Se Bond Formation at Bridging Vinyliminium Ligands in Diiron Complexes

Abstract The vinyliminium complexes [Fe 2 {μ‐η 1 :η 3 ‐C(R)C(R)CN(Me) 2 }(μ‐CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R = Me, 3a ; R = CO 2 Me, 3b ; R = Ph, 3c ) were treated with S 8 in the presence of t BuLi, undergoing fragmentation and affording the corresponding six‐membered metallacyclic complexes [Fe(Cp)(CO){SC(R)=C(R)C(NMe 2 )S}] ( 5a – c ). Complexes 5a – c result from cleavage of the diiron precursor and addition of S to the vinyliminium ligand to generate a dithiochelating ligand. Analogous reactions of the vinyliminium complexes [Fe 2 {μ‐η 1 :η 3 ‐C(R)C(R)CN(Me)(Xyl)}(μ‐CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R = Me, 3d ; R = CO 2 Me, 3e ), which contain a Xyl group (Xyl = 2,6‐Me 2 C 6 H 3 ) in place of a methyl, displayed a different outcome. Complex 3d afforded the diiron complex [Fe 2 {μ‐η 1 :η 3 ‐C(Me)=C(CS 2 )C=N(Me)(Xyl)}(μ‐CO)(CO)(Cp) 2 ] ( 10 ), whereas 3e led to the formation of the five‐membered metallacycle [Fe(Cp)(CO){C{N(Me)(Xyl)}C(CO 2 Me)C(CO 2 Me)S}] ( 11 ) together with the diiron complex [Fe 2 {μ‐η 1 :η 3 ‐C(CO 2 Me)=C(S)C=N(Me)(Xyl)}(μ‐CO)(CO)(Cp) 2 ] ( 12 ). The formation of 10 and 12 implies C–H and C–C cleavage, respectively, and C–S bond formation without rupture of the diiron framework. The vinyliminium complexes 3a – d and also [Fe 2 {μ‐η 1 :η 3 ‐C(Et)C(Et)CN(Me)(CH 2 Ph)}(μ‐CO)(CO)(Cp) 2 ][SO 3 CF 3 ] ( 3f ) reacted with gray selenium in the presence of t BuLi to afford the five‐membered metallacycles [Fe(Cp)(CO){C{N(Me)R}C(R′)C(R′)Se}] (R = R′ = Me, 13a ; R = Me, R′ = CO 2 Me, 13b ; R = Me, R′ = Ph, 13c ; R = Xyl, R′ = Me, 13d ; R = CH 2 Ph, R′ = Et, 13f ) in which one Se atom has been incorporated into the chelating ligand. The X‐ray molecular structures of 5a and 13a have been determined.