Novel anionic rearrangements in hexacarbonyldiiron complexes of chelating organosulfur ligands

Article abstract of DOI:10.1021/om00145a009

Bridging organosulfur chelate ligands of type -SCHRS- (R = H, Ph), -SCH₂CH₂S-, -S(CH₂)₃S-, and -SCH₂-o-C₆H₄CH₂S- in their Fe₂(CO)₆ complexes are deprotonated by lithium diisopropylamide. The resulting anion in the case of the -SCH₂CH₂S- ligand undergoes β-elimination to produce (μ-LiS)(μ-CH₂=CHS)Fe₂(CO)₆, but the anions derived from the other ligands undergo an intramolecular rearrangement which involves nucleophilic attack by the carbanion at an iron atom with displacement of an electron pair onto one of the sulfur atoms. Addition of an organic halide then results in alkylation of a sulfur atom. In the case of (μ-SCH₂S)Fe₂(CO)₆ this sequence results in formation of an Fe₂(CO)₆ complex of an alkyl dithioformate, (HC(S)SR)Fe₂(CO)₆. Complexes of the latter type also can be deprotonated. A similar anionic rearrangement then results in formation of novel RR′S-CS-[Fe(CO)₃]₂ complexes after alkylation of the intermediate sulfur-centered anion with R′X. The structures of three products of such reactions were determined by X-ray crystallography. (μ-CH₃C(O)CH₂SCHS)Fe₂(CO)₆ (10) crystallizes in the space group P1 (a = 10.296 (2) A?, b = 11.306 (2) A?, c = 6.617 (1) A?, α = 100.45 (1)°, β = 93.36 (1)°, γ = 103.38 (1)°, V = 732.9 A?³, and Z = 2). On the basis of 2073 observations and 194 parameters varied the structure has converged at R = 0.042 and R_w = 0.055. (μ-C₂H₅SCHC₆H₄CH ₂S)Fe₂(CO)₆ (19) crystallizes in P2₁/n (a = 15.003 (2) A?, b = 7.530 (1) A?, c = 16.599 (2) A?, β = 92.11 (1)°, V = 1874.0 A?³, and Z = 4) and has refined to R = 0.053 and R_w = 0.055 with 2004 observations and 223 parameters varied. (μ-SCS-(CH₃)₂)Fe₂(CO)₆ (22) crystallizes in P1 (a = 9.586 (1) A?, b = 10.276 (1) A?, c = 7.601 (1) A?, α = 92.18 (1)°, β = 111.52 (1)°, γ = 86.94 (1)°, V = 695.3 A?³, and Z = 2) and has refined to R = 0.029 and R_w = 0.039 with 2395 observations and 196 parameters varied.