Reactions of the thiocarbene complex Cp(CO)2Fe[CH(SMe)]+ with amines

Article abstract of DOI:10.1021/om50005a017

Pyridine (py) reacts with Cp(CO)₂Fe[CH(SMe)⁺, 1, to form the carbene adduct Cp(CO)₂Fe[CH-(SMe)(py)]⁺, 2. With primary (NH₂Me, NH₂Cy, NH₂-i-Pr, and NH₂-t-Bu) and secondary (HNMe₂, HNEt₂) amines and NH₃, 1 and 2 react to form the air-stable secondary aminocarbene complexes Cp(CO)₂Fe-[CH(NR₂)]⁺. The phosphite-substituted complex Cp(CO)(P(OPh)₃)Fe[CH(NEt₂)]⁺ was prepared similarly from Cp(CO)(P(OPh)₃)Fe[CH(SMe)]⁺ and HNEt₂. Nonequivalence of the alkyl groups in ¹NMR spectra of the complexes containing [CH(NMe₂)] and [CH(NEt₂)] carbene groups indicates a high barrier to rotation around the C(carbene)-N bond. The Cp(CO)₂Fe[CH(NHR)]⁺ complexes are deprotonated by the bases NaOH-EtOH and NaH to yield the formimidoyl complexes Cp(CO)₂Fe[CH(=NR)] which their ¹H NMR spectra indicate exist in anti and syn forms. The anti:syn ratio decreases with the R group in the order t-Bu > i-Pr > Cy. Methylation of Cp(CO)₂Fe[CH(=NR)] with MeOSO₂F gives a mixture of E and Z isomers of Cp(CO)₂Fe[CH(NMe-i-Pr)]⁺. Reactions of the Cp(CO)₂Fe[CH(NR₂)]⁺ (NR₂ = NHMe, NHCy, NH-t-Bu, and NMe₂) complexes with amine (HNR₂) lead to removal of the aminocarbene ligand from the metal, thereby giving the formamidinium ion HC(NR₂)₂⁺ together with Cp(CO)₂FeH. A mechanism involving β-hydrogen transfer from an N atom to the Fe is proposed. The reaction of Cp(CO)₂Fe[CH(NHCy)]⁺ with Me₃NO in MeCN, instead of giving products resulting from amine oxide attack at the carbene carbon, gives the stable CO-substituted product Cp(CO)(MeCN)Fe[CH(NHCy)]⁺, which can also be prepared by photolysis of Cp(CO)₂Fe[CH(NHCy)]⁺ in MeCN. New complexes are characterized by their IR and ¹H and ¹³C NMR spectra.