Synthesis and stereochemistry of diiron complexes generated from the reactions of iron carbonyls with 2-thienyl thiol and 2-thienyl methanethiol

Abstract

The reactions of Fe(CO)5 with 2-thienyl thiol and 2-thienyl methanethiol in the presence of Me3NO·2H2O formed the complexes Fe2(CO)6(μ-SR)2 (1, R=2-thienyl, 2-C4H3S; 2, R=2-thienylmethyl, 2-C4H3SCH2), each existing as an a/e isomer. The reactions of Fe3(CO)12 with 2-thienyl thiol and 2-thienyl methanethiol in the presence of Et3N generated the triethylammonium salts of the [(μ-RS)Fe2(CO)6(μ-CO)]− anions (m1, R=2-C4H3S; m2, R=2-C4H3SCH2). The reactions of the μ-CO-containing anion salts with PhCOCl afforded the complexes (μ-RS)Fe2(CO)6(μ-COPh) (3, R=2-C4H3S; 4, R=2-C4H3SCH2). In 3, the 2-C4H3S group is attached to the bridging S atom in an axial bonding fashion, whereas the 2-C4H3SCH2 group in 4 is bonded to the bridging S atom in an equatorial bonding manner. The reactions of the μ-CO-containing anion salts with Ph2PCl yielded the complexes (μ-RS)Fe2(CO)6(μ-PPh2) (5, R=2-C4H3S; 7, R=2-C4H3SCH2) as well as (μ-RS)Fe2(CO)5(μ-PPh2)(kP-Ph2PSR) (R=2-C4H3S, 6). In 6 and 7, the 2-C4H3S and 2-C4H3SCH2 groups are in equatorial bonding positions. The reactions of the μ-CO-containing anion salts with CS2 produced the triethylammonium salts of the [(μ-RS)Fe2(CO)6(μ-CS2)]− anions (m3, R=2-C4H3S; m4, R=2-C4H3SCH2). The reaction of the μ-CS2-containing anion m3 with PhCOCl in THF at −78°C gave the complex (μ-2-C4H3SS)Fe2(CO)6(μ-k2C:k2S-CSSCOPh) (8), in which the unprecedented ligand PhCOSCS acts as a five-electron donor. The reaction of the μ-CS2-containing anion m4 with MeI in THF at room temperature provided the complex (μ-2-C4H3SCH2S)Fe2(CO)6(μ-k2C,S-CSSCH3) (9). Upon treatment with Ph3P in the presence of Me3NO·2H2O, 3 and 4 afforded the complexes (μ-RS)Fe2(CO)5(μ-COPh)(PPh3) (10, R=2-C4H3S; 11, R=2-C4H3SCH2). In each case, Ph3P is coordinated to an Fe atom linked by the O atom of the μ-PhCO group. As with 3 and 4, the 2-C4H3S group in 10 is attached to the bridging S atom in an axial bonding mode, while the 2-C4H3SCH2 group in 11 is attached in an equatorial bonding manner. Treating 7 with Ph3P in the presence of Me3NO·2H2O produced the complex (μ-RS)Fe2(CO)5(μ-PPh2)(PPh3), with the R group in an equatorial bonding fashion (12, R=2-C4H3SCH2). The structures of all the complexes except 5 have been unequivocally determined by X-ray crystallography. Potential isomerizations in their solutions have been investigated using 1H, 13C and 31P NMR spectroscopy.