Electrophilically promoted cyanide abstraction in diiron cyano(amino) alkylidene complexes: molecular structure of [Fe2(CO)2(η-C5H5)2(µ-CO){µ-CN(CH2)4CH2}][(OC)5WCNW(CO)5]

Abstract

The reactions of the µ-cyano(amino)alkylidene complexes [Fe₂(CO)₂(cp)₂(µ-CO){µ-C(CN)(NR₂)}][cp η⁵-C₅H₅, NR₂ [graphic omitted]H₂1a or NMe₂1b] with [W(CO)₅(thf)](thf = tetrahydrofuran), MeSO₃CF₃ and HSO₃CF₃ electrophiles promotes µ-C–CN bond cleavage with formation of the corresponding [Fe₂(CO)₂(cp)₂(µ-CO)(µ-CNR₂)]⁺3. In the case of [W(CO)₅(thf)] the unexpected salts [Fe₂(CO)₂(cp)₂(µ-CO)(µ-CNR₂)][(OC)₅WCNW(CO)₅] have been prepared and characterized by the crystal structure of 3a[NR₂= [graphic omitted]H₂]. The structure [monoclinic, space group P2₁/n,a= 11.196(3), b= 17.389(3), c= 17.938(3)Å, β= 95.19(2)°, Z= 4, R= 0.032] contains ordered cations and anions. Distances of interest are Fe–µ-C(N) 1.875(6), C–N 1.280(8)Å in the cation and W–C(N) 2.184(8), W–N(C) 2.187(7) and C–N 1.15(1)Å in the anion, where the cyanide ligand symmetrically bridges two W(CO)₅ units. Electrophilic addition to phosphorus in [Fe₂(CO)₂(cp)₂(µ-CO){µ-C(CN)(PEt₂)}]2 has been observed and the adduct [Fe₂(CO)₂(cp)₂(µ-CO){µ-C(CN)[PEt₂W(CO)₅]}]4 spectroscopically characterized. The different reactivity of 1 and 2 with electrophilic reagents is attributed to the strong tendency to CN double-bond formation.