The pentacoordinate, 16-electron FeII complex [PPN][Fe(CO)2(CN)(S,NH-C6H4)] (1), stabilized by strong S, N π-donation of chelating [S,NH-C6H4]2- ligand, was prepared by the reaction of 2-aminophenyl disulfide and [PPN][Fe(CO)4(CN)]. Protonation of complex 1 by electrophiles (2-mercaptopyrimidine and 2-aminophenylthiol) yielded hexacoordinate iron(II)−thiolate cyanocarbonyl complexes [PPN][Fe(CO)(CN)(S-C4H3N2)2] (5) and [PPN][Fe(CO)2(CN)(S-C6H4NH2)(S,NH2-C6H4)] (3), respectively. The IR spectrum of complex 5 in the aprotic solvent CH3CN displayed a weak ν(CN) band at 2090 cm-1 and a strong ν(CO) band at 1945 cm-1. Chemical oxidation of complex 5 in CH3CN at − 20 °C with [Cp2Fe][PF6] displayed absorption bands at 2096 and 1962 cm-1 which were assigned to the ν(CN) and ν(CO) vibrational frequencies respectively of the thermally unstable neutral FeIII(CO)(CN)(S-C4H3N2)2. Complex 5 was reobtained upon addition of [PPN][BH4] to FeIII(CO)(CN)(S-C4H3N2)2 in CH3CN at −20 °C. The first dinuclear Fe(II)−thiolate cyanocarbonyl compound [PPN]2[(CN)(CO)2Fe(μ-S,S-C6H4)]2 (4), the promising structural and functional model compound of the dinuclear iron active sites of [Fe]-only hydrogenases isolated from D. desulfuricans and C. pasteurianum, was prepared by reacting 1,2-benzenedithiol with complex 1 in THF at −10 °C. The X-ray structural analysis shows that complex 4 possesses crystallographically imposed centrosymmetry. Two six-coordinate Fe(II) centers are connected via two thiolate bridges, and both CN- ligands point into the antiparallel direction. The IR spectrum of complex 4 in the aprotic solvent CH2Cl2 revealed a weak absorption band for the CN- ligands at 2101 cm-1, and two strong absorption bands for the CO groups at 2013 and 1960 cm-1. When the CH2Cl2 solution of complex 4 was exposed to 13CO at 0 °C, absorbances at 1968 and 1915 cm-1 appeared within 10 min. Reappearance of the 2013 and 1960 cm-1 bands on the removal of the 13CO and replacement with 12CO atmosphere demonstrated reversibility of the CO ligand lability of complex 4. The vibrational spectroscopies of the Fe(CO)2(CN) and Fe(CO)(CN) fragments (ν(CN) ranges from 2094 to 2105 cm-1, ν(CO) ranges from 1928 to 2013 cm-1) found in complexes 1, 3, 4, and 5 may be regarded as spectroscopic references of [Fe] hydrogenases in the various enzymatic states.

Diaminocarbenes, or "bottleable carbenes", have received considerable attention because they can be isolated and structurally characterized as free carbenes. [1][2][3][4] The electronic influence of the diamino groups is believed to be responsible for the carbene's stability as well as its nucleophilic character. Accordingly, these carbenes are good donors toward various metal ions. 5,6 An interesting example reported by Herrmann and co-workers 6 is bis(1,3,4,5-tetramethylimidazol-2-ylidene)palladium(II) iodide, which functions as a catalyst for the Heck reaction under extreme conditions. Transition metal complex mediated carbene transfer reactions are important tools for organic synthesis, but the simple transfer of carbene ligands between metal ions is rare. 7,8 Since diaminocarbene can act as a donor ligand, transfer between metal ions is amenable to study. In a previous investigation, we were able to (1) (a) Arduengo, A. J., III; Harlow, R. L.; Kline, M. J. Am. Chem. Soc. 1991, 113, 8782. (b) Arduengo, A. J., III; Dias, H. V. R.; Harlow, R. L.; Kline, M.

Formation of the N-arylated η 3 -aza-TMM complexes of iridium from regioselective hydroanilination of an octahedral (η 1 -allenyl)iridium complex has been studied. (OC-6-42)-In contrast, the reactions of 2 with XC 6 H 4 NH 2 (X ) F, NO 2 , MeO, H, Me), Ph 2 NH, and Ph(Me)NH result in regioselective addition at the allenyl ligand, thereby generating the N-arylated η 3 -aza-TMM complexes 5a-g. The mechanistic studies confirm that the hydroanilination is preceded by the formation of an aniline-ligated intermediate. † Based on the M.S. thesis of Y.-K.C.,

Deprotonation of cationic pentamethylcyclopentadienyl dppp ruthenium vinylidene complexes containing electron-withdrawing groups at the vinylidene ligand yielded cyclopropenylInsertion of acetone into the three-membered ring of 3a gave the neutral dihydrofuranyl complex [Ru]-CdC(Ph)CH(CN)CMe 2 O (4). Electrophilic addition at C β of 4 afforded cationic carbene complexes [[Ru]dCC(R′)(Ph)CH(CN)C(CH 3 ) 2 O] + (R′ ) CH 2 CN, 5a; R′ ) CH 2 CO 2 CH 3 , 5b; R′ ) H, 7; R′ ) HgCl, 8). Complexes 5a and 5b transformed to [[Ru]dCC(Ph)dC(CN)C(CH 3 ) 2 O] + (6) by elimination of small organic molecules. Reactivity of ruthenium complexes with a C 5 Me 5 ligand is different from those with a C 5 H 5 ligand and could be ascribed to electronic and steric effects. Reaction of [Ru]N 3 with ICH 2 CN gave [Ru]-NCH 2 I (11). Crystal structures of complexes 3a, 4, 6, 7, and 11 are also reported.