TRANSITION-METAL COMPLEXES WITH SULFUR LIGANDS .52. SYNTHESIS, X-RAY STRUCTURE CHARACTERIZATION, AND REACTIONS OF [FE(CO)(MU-S4)]2, A NOVEL TYPE OF CHIRAL COMPLEX WITH RELEVANCE TO IRON OXIDOREDUCTASES (S42- = 1,2-BIS((2-MERCAPTOPHENYL)THIO)ETHANATO(2-))

Searching for model complexes of hydrogenases and nitrogenases with chirotopic iron centers, we found that the thermal decarbonylation of [Fe(CO)2(“;S4”)] (1) leads to [Fe(CO)(µ-“S4”)]2(2) (“S4”2−- = l,2-bis((2-mercaptophenyl)thio)ethanato(2-)). 2 results from the connection of two homochiral [Fe(CO)(“S4”)] fragments and represents a new type of chiral complex. An analysis of theoretically possible isomers of 2 is given. One pair of enantiomers of 2 as well as 1 were characterized by X-ray structure determinations. 1: monoclinic, P21/c, a = 1293.3 (6) pm, b = 1258.2 (6) pm, c = 1151.9 (4) pm, β = 111.88 (4)°, Z = 4, dcaled = 1.60 g/cm3, R (Rw) = 0.068 (0.054). 2: monoclinic, P21c, a = 1272.8 (5) pm, b = 1534.1 (23) pm, c = 1633.6 (16) pm, β = 104.76 (8)°, Z = 4, dcaled= 1.69 g/cm3, R (RJ = 0.078 (0.065). The iron center of 1 is pseudooctahedrally coordinated by four sulfur and two carbon atoms. In 2, the iron centers are coordinated pseudooctahedrally by five sulfur and one carbon atom and bridged via two thiolato-S atoms. The trans coordination of the thiolato-S atoms in 1 is retained in 2. The chirotopic iron centers of 2 possess latent coordination sites and low-valent Fe centers capable of binding σ−π donors. In order to substitute or to transform the CO ligands, 2 was reacted with NO+, NO, PMe3, and MeLi. With NOPF6, a CO/NO+substitution took place, yielding [Fe2(CO)(NO)(ε-“S4”)2]PF6(3), which is isoelectronic to 2. Treatment of 2 with NO gas or PMe3led to cleavage of Fe—thiolato-S bridges and formation of mononuclear [Fe(NO)2(“S4”)] (4) and [Fe(CO)(PMe3)(“S4”)] (5), respectively. The reaction between 2 and MeLi caused the elimination of the C2H4bridge from the tetradentate “S4”2−ligand under formation of [Fe(“S2”)2]22−(6) (“S2”2−= 1,2-benzenedithiolate), which could be isolated as a AsPh4+salt. The mutual influence of the Fe centers in 2 and 3 was investigated by Mossbauer spectroscopy. © 1990, American Chemical Society. All rights reserved.