ELECTROPHILICALLY PROMOTED CYANIDE ABSTRACTION IN DIIRON CYANO(AMINO)ALKYLIDENE COMPLEXES - MOLECULAR-STRUCTURE OF [FE2(CO)2(ETA-C5H5)2(MU-CO)(MU-CN(CH2)4CH2)]-[(OC)5WCNW(CO)5]

The reactions of the mu-cyano(amino)alkylidene complexes [Fe2(CO)2(cp)2(mu-CO){mu-C(CN)(NR2)}] [cp = eta5-C5H5, NR2 = N(CH2)4CH2 1a or NMe2 1b) with [W(CO)5(thf)] (thf = tetrahydrofuran), MeSO3CF3 and HSO3CF3 electrophiles promotes mu-C-CN bond cleavage with formation of the corresponding [Fe2(CO)2(cp)2(mu-CO) (mu-CNR2)]+3. In the case of [W(CO)5(thf)] the unexpected salts [Fe2(CO)2(cp)2(mu-CO)(mu-CNR2)][(OC)5WCNW(CO)5] have been prepared and characterized by the crystal structure of 3a[NR2 = N(CH2)4CH2]. The structure [monoclinic, space group P2(1)/n,a = 11.196(3), b = 17.389(3), c = 17.938(3) angstrom, beta = 95.19(2)-degrees, Z = 4, R = 0.032] contains ordered cations and anions. Distances of interest are Fe-mu-C(N) 1.875(6), C-N 1.280(8) angstrom in the cation and W-C(N) 2.184(8), W-N(C) 2.187(7) and C-N 1.1 5(1) angstrom in the anion, where the cyanide ligand symmetrically bridges two W(CO)5 units. Electrophilic addition to phosphorus in [Fe2(CO)2(cp)2(mu-CO){mu-C(CN)(PEt2)}] 2 has been observed and the adduct [Fe2(CO)2(cp)2(mu-CO){mu-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 C=N double-bond formation.