Ferrous Carbonyl Dithiolates as Precursors to FeFe, FeCo, and FeMn Carbonyl Dithiolates

Abstract

Reported are complexes of the formula Fe(dithiolate)(CO)2(diphos) and their use to prepare homo- and heterobimetallic dithiolato derivatives. The starting iron dithiolates were prepared by a one-pot reaction of FeCl2 and CO with chelating diphosphines and dithiolates, where dithiolate = S2(CH2)22– (edt2–), S2(CH2)32– (pdt2–), S2(CH2)2(C(CH3)2)2– (Me2pdt2–) and diphos = cis-C2H2(PPh2)2 (dppv), C2H4(PPh2)2 (dppe), C6H4(PPh2)2 (dppbz), C2H4[P(C6H11)2]2 (dcpe). The incorporation of 57Fe into such building block complexes commenced with the conversion of 57Fe into 57Fe2I4(iPrOH)4, which then was treated with K2pdt, CO, and dppe to give 57Fe(pdt)(CO)2(dppe). NMR and IR analyses show that these complexes exist as mixtures of all-cis and trans-CO isomers, edt2– favoring the former and pdt2– the latter. Treatment of Fe(dithiolate)(CO)2(diphos) with the Fe(0) reagent (benzylideneacetone)Fe(CO)3 gave Fe2(dithiolate)(CO)4(diphos), thereby defining a route from simple ferrous salts to models for hydrogenase active sites. Extending the building block route to heterobimetallic complexes, treatment of Fe(pdt)(CO)2(dppe) with [(acenaphthene)Mn(CO)3]+ gave [(CO)3Mn(pdt)Fe(CO)2(dppe)]+ ([3d(CO)]+). Reduction of [3d(CO)]+ with BH4– gave the Cs-symmetric μ-hydride (CO)3Mn(pdt)(H)Fe(CO)(dppe) (H3d). Complex H3d is reversibly protonated by strong acids, the proposed site of protonation being sulfur. Treatment of Fe(dithiolate)(CO)2(diphos) with CpCoI2(CO) followed by reduction by Cp2Co affords CpCo(dithiolate)Fe(CO)(diphos) (4), which can also be prepared from Fe(dithiolate)(CO)2(diphos) and CpCo(CO)2. Like the electronically related (CO)3Fe(pdt)Fe(CO)(diphos), these complexes undergo protonation to afford the μ-hydrido complexes [CpCo(dithiolate)HFe(CO)(diphos)]+. Low-temperature NMR studies indicate that Co is the kinetic site of protonation.

Models of the Ni-L and Ni-SIa States of the [NiFe]-Hydrogenase Active Site

“…The diphosphine in complexes [ 1a – 1d ]BF 4 is only observed in the dibasal arrangement, whereas other Fe(dithiolate)-(diphosphine)CO compounds have been shown to adopt both a dibasal and an apical–basal arrangement. 33 The phosphorus centers remain NMR-equivalent at −90 °C, suggesting either an exceptionally low barrier for isomerization or the presence of a single isomer. In the IR spectrum, only a single isomer is observed, which, like the enzyme’s active site, has both donor ligands in basal positions.…”

“…Similar bimetallic hydrides have been known to adopt different isomers. 22,47 Furthermore, recent work suggests that the protonation of (dppe)Ni(pdt)-Fe(CO) 3 proceeds via an unobserved isomer. 21 …”

“…Compound [ 1c ]BF 4 was prepared in a fashion similar to that of [ 1a ]BF 4 using Fe(Me 2 pdt)(dppe)(CO) 2 22 as the iron source. Yield: 77%, dark-red powder.…”

Synthesis of Diiron(I) Dithiolato Carbonyl Complexes

“…with Fe(bda)(CO) 3 at room temperature affords Fe 2 ( μ -pdt)(CO) 4 (diphos) in 60–83% yields (eq 28). 425 …”

New Tetracobalt Cluster Compounds for Electrocatalytic Proton Reduction: Syntheses, Structures, and Reactivity

“…[13] More recently, the same group reported the preparation of a series of heteronuclear FeMn and FeCo complexes by using ferrous carbonyl dithiolates as precursors, but the electrochemical properties of these complexes were not reported. [14] On the other hand, Sun and co-workers reported a family of efficient electrocatalysts (MP 4 N 2 ; M= Fe, Co) for hydrogen production when applied in neutral water at a low overpotential. With the same ligand, the corresponding P 4 N 2 cobalt complex has a higher efficiency and lower overpotential than its iron analogue.…”