摘要
A number of thermally stable iron(II)-thiolate cyanocarbonyl complexes, cis,cis-[Fe(CN) 2 (CO) 2 (CS 3 -S,S)] 2- (1), mer-[Fe(CO) 2 (CN) 3 (NCCH 3 )] - (2) mer-[Fe(CO) 3 (CN)(CS 3 -S,S)] - (3), cis-[Fe(CO) 2 (CN)(S(CH 2 ) 2 S (CH 2 ) 2 S(CH 2 ) 2 S-S,S,S)] - (4), [Fe(CO) 2 (CN) 3 Br] 2- (5), mer-[Fe(CO) 2 (CN) 3 (m-SC 6 H 4 Br)] 2- (6) and mer-[Fe(CO) 2 (CN) 3 (SPh)] 2- (7) were isolated and characterized by IR and X-ray diffraction analysis. The extrusion of one strong σ-donor CN - ligand instead of CO from the iron(II) center of the thermally stable complexes [Fe II (CO) 2 (CN) 3 Br] 2- (5) containing less electron-donating bromide reflects the electron-rich character of the mononuclear [Fe II (CN) 2 (CO) 2 (CS 3 - S,S)] 2- (1) when ligated by the bidentate thiolate, and the combination of one cyanide, two carbonyls and a tridentate thiolate provides the stable complex 4 as a result of the reaction of complex 5 and chelating ligand [S(CH 2 ) 2 S(CH 2 ) 2 S] 2- . The preference of the sixth ligand coordinated to the unsaturated [Fe II (CO)(CN) 2 (CS 3 -S,S)] 2- Fe(II) center, the iron-site architecture of the bimetallic Ni-Fe active-site of [NiFe] hydrogenases, is a strong π-acceptor CO group. Scrutiny of the coordination chemistry of iron(II)-thiolate cyanocarbonyl species [Fe II (CO) x (CN) y (SR) z ] n- reveals that certain combinations of thiolate, cyanide and carbonyl ligands(3 ≤ y + z ≤ 4) bound to Fe(II) are stable and this could point the way to understand the reasons for Nature's choice of combinations of these ligands in hydrogenases.