Iron(II) aryldiazene complexes: preparation, characterization, and ligand-substitution reactions with ketones, nitriles, and isocyanides. Crystal structure of the diazene precursor, the new hydride, trans-carbonylhydridotetrakis(triethyl phosphite)iron tetraphenylborate, trans-[FeH(CO){P(OEt)3}4]BPH4

Iron hydride complexes, trans-[FeH(CO)L4]BPh4(L = P(OMe)3, P(OEt)3, PhP(OEt)2), were prepared by allowing [FeX(CO)L4]+(X = Cl, Br) derivatives to react with zinc in acetonitrile solution; the crystal structure of trans-[FeH(CO){P(OEt)3j4]BPh4was determined. The compound crystallized in the orthorhombic space group P212121 with four molecules per unit cell and lattice parameters a-23.658 (14) A, b = 23.671 (13) A, and c = 10.507 (6) A. The structure was solved by the heavy-atom technique and refined to R = 0.0756 for 2813 independent reflections having / > 2σ(I). The environment of the iron atom is that of a distorted octahedron, the ligands being one hydride ion, one carbonyl group, and four phosphite groups. The complex [FeH(CO)|P(OEt)3j4]+undergoes insertion reactions with aryldiazonium cations to afford the first iron(II) diazene derivatives, (Ar = 4-CH3C6H4, 4-ClC6H4). The 1H NMR spectrum of the 15N-labeled complex (J15NH= 67 Hz) excludes the existence of an arylhydrazido(2~) derivative. The reaction of these diazene compounds with ketones was examined and led to the synthesis of new O-bonded (R-R’-CH3; R-CH3, R’ = C2H5; R = CH3, R’ = C6H5; R, R/= (CH2)5 (cyclohexanone)) ketone complexes. Furthermore, carbonyl, isocyanide, and nitrile derivatives of the type cis-[Fe(CO)2L4](BPh4)2, cis-[Fe(CO)(RNC)L4](BPh4)2(R = C6H5, 4-CH3C6H4, 4-CH3OC6H4, 2,6-(CH3)2C6H3, 4-N02C6H4), and trans-[Fe(CO)(RCN)L4](BPh4)2(R = C6H5, 4-CH3C6H4, 2-CH3C6H4, CH3, NC(CH2)4) were obtained; their characterization by infrared and 1H and 31P NMR data is also reported. The nitrile complexes show v(CN) increased in comparison to the free-ligand value.