Carbon- and Sulfur-Bridged Diiron Carbonyl Complexes Containing N,C,S-Tridentate Ligands Derived from Functionalized Dibenzothiophenes: Mimics of the [FeFe]-Hydrogenase Active Site

Abstract

Photochemical reactions of [Fe(CO)5] with dibenzothiophene (DBT) derivatives bearing a N-donor group produced a series of C,S-bridged diiron carbonyl complexes [{Fe(μ-L′-κ3 N,C,S)(CO)2}Fe(CO)3], as previously reported for 4-(2′-pyridyl)dibenzothiophene (L1), where L′ represents the N,C,S-tridentate ligands L1′–L5′, formed by C–S bond cleavage of L1–L5, respectively. The DBT derivatives used in this study have Schiff base or oxazoline moieties at the 4-position: L2 = PhCH2NCH-DBT, L3 = 2-MeOC6H4CH2NCH-DBT, L4 = (S)-PhC(Me)HNCH-DBT, L5 = (R)-4-isopropyl-2-oxazolinyl-DBT. The diiron complexes were characterized by NMR, absorption, and circular dichroism spectroscopy, and the dinuclear structures bridged by thiolate S and aryl C atoms were established by X-ray crystallography. The diiron complex [{Fe(μ-L′-κ3 N,C,S)(CO)2}Fe(CO)3] consists of two units, Fe(L′)(CO)2 and Fe(CO)3: the latter unit is located on a thiolate-containing metallacycle in the former one. The chiral Schiff base ligand precursor L4 gave a 55:45 mixture of two diastereomers for [{Fe(μ-L4′-κ3 N,C,S)(CO)2}Fe(CO)3], while chiral L5 with an (R)-4-isopropyl-2-oxazolinyl group afforded [{Fe(μ-L5′-κ3 N,C,S)(CO)2}Fe(CO)3] in a 9:1 diastereomeric ratio. The diiron carbonyl complexes of the N,C,S-tridentate ligands (L1′L5′) showed two reversible redox couples for [Fe2(μ-L′)(CO)5]0/– and [Fe2(μ-L′)(CO)5]−/2–. The two-electron-reduced forms undergo protonation and act as electrocatalysts for proton reduction of acetic acid in acetonitrile.

Systematic Structure-Activity Relationship (SAR) Exploration of Diarylmethane Backbone and Discovery of A Highly Potent Novel Uric Acid Transporter 1 (URAT1) Inhibitor

“…1 H-NMR (CDCl 3 , 400 MHz) δ: 10.27 (s, 1H), 8.40 (d, J = 7.6 Hz, 1H), 8.17–8.22 (m, 1H), 7.93–7.97 (m, 2H), 7.64 (t, J = 7.6 Hz, 1H), 7.47–7.54 (m, 2H). The 1 H-NMR data were in good agreement with those reported [ 55 ].…”

Synthesis of unsymmetrical 5,6-POCOP′-type pincer complexes of nickel(ii): impact of nickelacycle size on structures and spectroscopic properties

“…On the other hand, recent reports have shown a growing interest in the structures and reactivities of nonsymmetrical EXE´-type ligands based on both different donor moieties and differently-sized metallacycles, including : 5,6-NCS; 8 5,6-SCN; 9 5,6-POCN; 10 3,6-, 3,7-, and 4,5-PNP´; 11 5,6-PCN; 12 5,6-POCOP´. On the other hand, recent reports have shown a growing interest in the structures and reactivities of nonsymmetrical EXE´-type ligands based on both different donor moieties and differently-sized metallacycles, including : 5,6-NCS; 8 5,6-SCN; 9 5,6-POCN; 10 3,6-, 3,7-, and 4,5-PNP´; 11 5,6-PCN; 12 5,6-POCOP´.…”

Formation, reactivity and redox properties of carbon- and sulfur-bridged diiron complexes derived from dibenzothienyl Schiff bases: effect of N,N- and N,P-chelating moieties

“…Furthermore, an electronic absorption band at 552 nm (ε = 2800 dm 3 mol −1 cm −1 ) for 2, which is assigned to metal-to-ligand charge transfer (MLCT) transitions, is similar to those for related diiron complexes of S,C,N-tridentate Schiff base ligands. 20,21 These results suggest that complex 2 has a dinuclear structure containing BPT-NN as an S,C,N-tridentate ligand as depicted in Scheme 1.…”

“…1). 20 These complexes have an asymmetric structure with a polarized Fe-Fe bond, and show two one-electron reduction processes and electrocatalytic ability for proton reduction. The redox potentials of the C,S-bridged diiron complexes [{Fe(μ-L′-κ 3 S,C,N)(CO) 2 }Fe(CO) 3 ] did not depend on the type of the N donor moieties in the tridentate ligands.…”

“…The redox potentials of the C,S-bridged diiron complexes [{Fe(μ-L′-κ 3 S,C,N)(CO) 2 }Fe(CO) 3 ] did not depend on the type of the N donor moieties in the tridentate ligands. 20 To tune precisely the redox potentials of the asymmetric diiron complexes, the regioselective substitution for CO on the two iron centers is desired. Reactivity of [{Fe(μ-PyBPT-κ 3 S,C,N)-(CO) 2 }Fe(CO) 3 ] toward phosphines, however, is different from that of [Fe 2 (μ-dithiolate)(CO) 6 ]: excess of phosphines leads to the heterolytic Fe-Fe cleavage to give mononuclear iron(II) and iron(0) complexes.…”