Nitrosyl complexes: The 18-electron dinitrosyl complexes CpW(NO)(,2)(L)('+). (Cp=(eta)('5)-C(,5)H(,5)), where L is P(OPh)(,3), PPh(,3), or P(OMe)(,3), undergo a one-electron reduction when reacted with alkoxides, hydrazine, or zinc to yield the purple, air-sensitive, 19-electron, neutral complexes CpW(NO)(,2)(L). Cyclic voltammetric studies show these to be quasireversible reductions with the reduction potentials becoming more negative with L in the order: P(OPh)(,3) > P(OMe)(,3) > PPh(,3). ESR spectra of the CpW(NO)(,2)(L) complexes exhibit a ten-line pattern resulting from hyperfine coupling of the unpaired electron with the ('31)P and two equivalent ('14)N nuclei. A single crystal X-ray diffraction study of CpW(NO)(,2)(P(OPh)(,3)) shows that the N-W-N bond angle (102.7(DEGREES)) in this complex is significantly larger than that (92.0(DEGREES)) in the 18-electron analog CpW(NO)(,2)Cl. Also, the 19-electron complex has shorter W-N but longer N-O bonds than in CpW(NO)(,2)Cl. The differences between the 18- and 19-electron structures indicate that the 19th electron occupies an orbital which has substantial NO 2(pi) character and is antibonding between the two NO ligands and antibonding between the N and O atoms of each NO ligand. The 19-electron complex is readily oxidized back to the CpW(NO)(,2) (P(OPh)(,3))('+) cation by a variety of agents such as Ag('+), Ph(,3)C('+), MeOSO(,2)F, CF(,3)SO(,3)H, and I(,2);Carbene complexes: The Cp(CO)(L)FeCH(SMe)('+) (Cp=(eta)('5)-C(,5)H(,5), L=CO, PPh(,3), P(OPh)(,3)) complexes have been prepared by the reaction of Cp(CO)(L)FeCH(SMe)(,2) and CF(,3)SO(,3)H. The phosphine and phosphite derivatives are modestly stable to moisture while the dicarbonyl complex decomposes in H(,2)O to afford Cp(CO)(,3)Fe('+) and Cp(CO)(,2)FeCH(,2)SMe. Cp(CO)(,2)FeCH(SMe)('+) readily reacts with L' (PPh(,2)Me, PPh(,3), ClPPh(,2), PCl(,3), P(OPh)(,3), P(OCH(,2))(,3)CMe, PPh(,2)H, PCy(,2)H, PPhH(,2), PCyH(,2), pyridine) to give the corresponding adducts, Cp(CO)(,2)FeCH(SMe)(L')('+). An x-ray structural determination of the P(OCH(,2))(,3)CMe adduct was completed and reveals a bond distance of 1.732 (ANGSTROM) for the bond between the formerly carbene carbon (Cl) and the phosphorus atom. The Fe-Cl bond (2.08 (ANGSTROM)) is expected for a normal (sigma) bond. The PPh(,3) and P(OCH(,2))(,3)CMe adducts decompose in the solid state when heated at above 180(DEGREES)C to afford Cp(CO)(,2)Fe(PPh(,3))('+) and Cp(CO)(,2)FeP(OCH(,2))(,3)CMe('+), respectively, and MeSCH=CHSMe.