REACTIVITY OF HYDRIDES FEH2(CO)(2)P-2 (P = PHOSPHITES) WITH ARYLDIAZONIUM CATIONS - PREPARATION, CHARACTERIZATION, X-RAY CRYSTAL-STRUCTURE,AND ELECTROCHEMICAL STUDIES OF MONONUCLEAR AND BINUCLEAR ARYLDIAZENIDO COMPLEXES

Mono- and binuclear aryldiazenido complexes [Fe(ArN2)(CO)(2)P-2]BPh4 ( 1-4) and [{Fe(CO)(2)P-2}(2)(mu-N2Ar-ArN2)]BPh4)(2) (5-8) [P = P(OEt)(3 ), PPh(OEt)(2), PPh2OEt, P(OPh)(3); Ar = C6H5, 2-CH3C6H4, 4-CH3C6H4; A r-Ar = 4,4'-C6H4-C6H4, 4,4'-(2-CH3)C6H3-C6H3(2-CH3), 4,4'-C6H4-CH2-C6H 4] were prepared by allowing hydride species FeH2(CO)(2)P-2 to react w ith an excess of mono- (ArN2)(BF4) or bis-aryldiazonium (N2Ar-ArN2)(BF 4)(2) salts, respectively, at low temperature. A reaction path involvi ng a hydride-aryldiazene intermediate [FeH(ArN=NH)(CO)(2)P-2](+), whic h, through the loss of H-2, affords the final aryldiazenido complexes 1-8, is proposed. The compounds were characterized by H-1 and P-31{H-1 } NMR spectroscopy (including N-15 isotopic substitution) and X-ray cr ystal structure determination. The complex O)(2){P(OEt)(3)}(2){mu-4,4' -N-2(2-CH3)C6H3-C6H3(2- CH3)N-2}](BPh4)(2) (5b) crystallizes in the sp ace group P (1) over bar with a = 15.008(4) Angstrom, b = 17.094(5) An gstrom, c = 10.553(3) Angstrom, alpha = 99.56(1)degrees, beta = 102.80 (1)degrees, gamma = 65.30(1)degrees, and Z = 1. The structure is centr osymmetric and consists of binuclear cations with the two iron atoms i n a quite regular trigonal bipyramidal environment, with the two CO in the equatorial and the two phosphites in the apical position, respect ively. Aryldiazenido complexes 1-8 react with strong acids HX (X = Cl, CF3SO3, CF3CO2) to give the corresponding aryldiazene derivatives, ac cording to the equilibrium [Fe(ArN2)(CO)(2)P-2](+) HX reversible arrow [FeX(ArN=NH)(CO)(2)P-2](+). Electrochemical studies of both mono- (1- 4) and binuclear (5-8) compounds were undertaken, and a mechanism for oxidation and reduction processes is proposed.