摘要
The pentacoordinate, 16-electron Fe(II) complex [PPN][Fe(CO) 2 (CN)(S,NH- C 6 H 4 )] (1), stabilized by strong S, N π-donation of chelating [S,NH- C 6 H 4 ] 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-C 4 H 3 N 2 ) 2 ] (5) and [PPN][Fe(CO) 2 (CN)(S-C 6 H 4 NH 2 )(S,NH 2 -C 6 H 4 )] (3), respectively. The IR spectrum of complex 5 in the aprotic solvent CH 3 CN displayed a weak υ(CN) band at 2090 cm -1 and a strong υ(CO) band at 1945 cm -1 . Chemical oxidation of complex 5 in CH 3 CN at - 20 °C with [Cp 2 Fe] [PF 6 ] displayed absorption bands at 2096 and 1962 cm -1 which were assigned to the υ(CN) and υ(CO) vibrational frequencies respectively of the thermally unstable neutral Fe(III)(CO)(CN)(S-C 4 H 3 N 2 ) 2 . Complex 5 was reobtained upon addition of [PPN]-[BH 4 ] to Fe(III)(CO)(CN)(S-C 4 H 3 N 2 ) 2 in CH 3 CN at -20 °C. The first dinuclear Fe(II)-thiolate cyanocarbonyl compound [PPN] 2 [(CN)(CO) 2 Fe(μ-S,S-C 6 H 4 )] 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 CH 2 Cl 2 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 CH 2 Cl 2 solution of complex 4 was exposed to 13 CO 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 13 CO and replacement with 12 CO 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 (υ(CN) ranges from 2094 to 2105 cm -1 , υ(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.