Unprecedented Zwitterionic Iminium−Chalcogenide Bridging Ligands in Diiron Complexes

The diiron vinyliminium complexes [Fe2{μ-η1:η3-C(R‘)CHCN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] [R = Xyl, R‘ = Me, 1a; R = Xyl, R‘ = Tol, 1b; R = Xyl, R‘ = CO2Me, 1c; R = Xyl, R‘ =
CH2OH, 1d; R = Xyl, R‘ = Bun, 1e; R = Me, R‘ = Me, 1f; R = Me, R‘ = Tol, 1g; R = Me, R‘ =
CO2Me, 1h; R = Me, R‘ = Bun, 1i; R = Me, R‘ = CH2OH, 1l; R = p-C6H4-CN, R‘ = Tol, 1m; R =
p-C6H4-OMe, R‘ = Me, 1n; Tol = 4-C6H4-Me; Xyl = 2,6-Me2C6H3] react with elemental sulfur or
selenium, in the presence of NaH, to give the zwitterionic vinyliminium compounds [Fe2{μ-η1:η3-C(R‘)C(E)CN(Me)(R)}(μ-CO)(CO)(Cp)2] [R = Xyl, R‘ = Me, E = S, 2a; R = Xyl, R‘ = Tol, E = S, 2b;
R = Xyl, R‘ = CO2Me, E = S, 2c; R = Xyl, R‘ = CH2OH, E = S, 2d; R = Xyl, R‘ = Bun, E = S, 2e;
R = Xyl, R‘ = Me, E = Se, 3a; R = Xyl, R‘ = Tol, E = Se, 3b; R = Me, R‘ = Me, E = Se, 3c; R =
Me, R‘ = Tol, E = Se, 3d; R = Me, R‘ = CO2Me, E = Se, 3e; R = Me, R‘ = Bun, E = Se, 3f; R =
Me, R‘ = CH2OH, E = Se, 3g]. Similarly, the reaction of 1a with Me3NO/NaH results in the formation
of [Fe2{μ-C(Me)C(O)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (4), in which the bridging ligand is better described
as a bis-alkylidene. The reactions of 1a,c with S8/NaH afford also the five-membered metallacycles [Fe(Cp)(CO){Cα(NMe(Xyl))Cβ(H)Cγ(R‘)S}] [R‘ = Me, 6a; R‘ = CO2Me, 6b], as secondary products, in
about 15% yield. Conversely, complexes [Fe2{μ-η1:η3-C(R‘)CHCN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3], 1f−h,m,n, react with S8/NaH, giving selectively the five-membered metallacycles [Fe(Cp)(CO){C(R‘)C(H)C{N(Me)(R)}S}] [R = Me, R‘ = Me, 7a; R = Me, R‘ = Tol, 7b; R = Me, R‘ = CO2Me,
7c; R = p−C6H4−CN, R‘ = Tol, 7d; R = p-C6H4-OMe, R‘ = Me, 7e]. The molecular structures of
2b·CH2Cl2, 3a, 4, 6a, and 7b have been determined by X-ray diffraction studies.

二铁乙烯亚胺络合物[Fe₂{μ-η¹:η³-C(R')=CHC=N(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃]（其中Cp为环戊二烯基Cyclopentadienyl）包含以下具体物种：当R=二甲苯基(Xyl，即2,6-二甲基苯基2,6-Me₂C₆H₃)、R'=甲基(Me)时为1a；R=Xyl、R'=对甲苯基(Tol，即4-甲基苯基4-C₆H₄-Me)时为1b；R=Xyl、R'=甲氧羰基(CO₂Me)时为1c；R=Xyl、R'=羟甲基(CH₂OH)时为1d；R=Xyl、R'=正丁基(Bun)时为1e；R=Me、R'=Me时为1f；R=Me、R'=Tol时为1g；R=Me、R'=CO₂Me时为1h；R=Me、R'=Bun时为1i；R=Me、R'=CH₂OH时为1l；R=对氰基苯基(p-C₆H₄-CN)、R'=Tol时为1m；R=对甲氧基苯基(p-C₆H₄-OMe)、R'=Me时为1n。
该类络合物在氢化钠(NaH)存在下，与单质硫或硒反应，可得到两性离子型二铁乙烯亚胺络合物[Fe₂{μ-η¹:η³-C(R')=C(E)C=N(Me)(R)}(μ-CO)(CO)(Cp)₂]，具体产物如下：当R=Xyl、R'=Me、E=硫(S)时为2a；R=Xyl、R'=Tol、E=S时为2b；R=Xyl、R'=CO₂Me、E=S时为2c；R=Xyl、R'=CH₂OH、E=S时为2d；R=Xyl、R'=Bun、E=S时为2e；R=Xyl、R'=Me、E=硒(Se)时为3a；R=Xyl、R'=Tol、E=Se时为3b；R=Me、R'=Me、E=Se时为3c；R=Me、R'=Tol、E=Se时为3d；R=Me、R'=CO₂Me、E=Se时为3e；R=Me、R'=Bun、E=Se时为3f；R=Me、R'=CH₂OH、E=Se时为3g。
类似地，1a与三甲基胺N-氧化物(Me₃NO)/NaH反应，可生成[Fe₂{μ-C(Me)C(O)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂]（产物4），该物种的桥联配体更适宜被描述为双亚烷基配体。
1a与1c分别与八硫环(S₈)/NaH反应时，还会生成收率约15%的五元金属杂环副产物[Fe(Cp)(CO){C_α(NMe(Xyl))C_β(H)C_γ(R')S}]，其中R'=Me时为6a，R'=CO₂Me时为6b。
与之相对，络合物1f–1h、1m、1n（即[Fe₂{μ-η¹:η³-C(R')=CHC=N(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃]）与S₈/NaH反应时，可选择性生成五元金属杂环[Fe(Cp)(CO){C(R')C(H)C{N(Me)(R)}S}]，具体产物包括：R=Me、R'=Me时为7a；R=Me、R'=Tol时为7b；R=Me、R'=CO₂Me时为7c；R=p-C₆H₄-CN、R'=Tol时为7d；R=p-C₆H₄-OMe、R'=Me时为7e。
已通过X射线衍射(X-ray diffraction)实验测定了2b·CH₂Cl₂、3a、4、6a及7b的分子晶体结构。