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.

Active site mimics of [FeFe]-hydrogenase are shown to be bidirectional catalysts, producing H2 upon treatment with protons and reducing equivalents. This reactivity complements the previously reported oxidation of H2 by these same catalysts in the presence of oxidants. The complex Fe2(adtBn)(CO)3(dppv)(PFc*Et2) ([1]0; adtBn = (SCH2)2NBn, dppv = cis-1,2-bis(diphenylphosphino)ethylene, PFc*Et2 = Et2PCH2C5Me4FeCp*) reacts with excess [H(OEt2)2]BArF4 (BArF4– = B(C6H3-3,5-(CF3)2)4–) to give ∼0.5 equiv of H2 and [Fe2(adtBnH)(CO)3(dppv)(PFc*Et2)]2+ ([1H]2+). The species [1H]2+ consists of a ferrocenium ligand, an N-protonated amine, and an FeIFeI core. In the presence of additional reducing equivalents in the form of decamethylferrocene (Fc*), hydrogen evolution is catalytic, albeit slow. The related catalyst Fe2(adtBn)(CO)3(dppv)(PMe3) (3) behaves similarly in the presence of Fc*, except that in the absence of excess reducing agent it converts to the catalytically inactive μ-hydride derivative [μ-H3]+. Replacement of the adt in [1]0 with propanedithiolate (pdt) results in a catalytically inactive complex. In the course of synthesizing [FeFe]-hydrogenase mimics, new routes to ferrocenylphosphine ligands and nonamethylferrocene were developed.

We report a biobased route to methacrylic acid via selective decarboxylation of itaconic acid utilizing catalytic ruthenium carbonyl propionate in an aqueous solvent system. High selectivity (>90%) was achieved at low catalyst loading (0.1 mol %) with high substrate concentration (5.5 M) at low temperature (200−225 °C) and pressure (≤425 psig) relative to previous contributions in this area. Direct decarboxylation of itaconic acid was achieved as opposed to the conjugate base reported previously, thereby avoiding basification and acidification steps. Also investigated was catalytic manganese(II) oxalate (5 mol %), but low yield (4.8%) and evolution of carbon monoxide via oxalate decomposition was problematic. Attempts at stabilization of the catalyst with triphenylphosphine were unsuccessful, but it exhibited greater catalytic efficacy (14.0% yield) than the manganese catalyst (4.8% yield) at 5 mol %. Neither carbon monoxide nor propylene (excessive decarboxylation) were detected during ruthenium-catalyzed decarboxylation. In addition, cosolvents such as tetraglyme lowered vapor pressures within the reaction vessel by >100 psig while minimizing decomposition of starting acids. In combination, these findings represent improvements over existing methodologies that may facilitate sustainable production of methacrylic acid, an important petrochemically based monomer for the plastics industry.

This review will highlight major advances in the synthesis and study of active site analogs for the [NiFe]‐, [FeFe]‐, and [Fe]‐hydrogenases (H 2 ases). In their biological role, the [NiFe]‐ and [FeFe]‐ H 2 ases utilize a combination of redox and acid–base reactions for the activation and formation of H 2 . Both reactions have been demonstrated in models. Relevant to the [NiFe]‐H 2 ases, models have been developed that form hydrides via the biologically relevant pathways of protonation or activation of H 2 . These hydrides serve as catalysts for the reduction of protons or oxidation of H 2 via mixed‐valence intermediates. These studies suggest that the hydride bridges the two metals unsymmetrically, and the Fe– H … Ni center engages in dihydrogen bonding to protic reagents as an intermediate in the formation and activation of H 2 . For the [FeFe]‐H 2 ases, the most informative models feature both an azadithiolate cofactor, which serves as a proton relay, and a terminal hydride ligand. Diiron species undergo oxidation to mixed‐valence Fe(I)Fe( II ) cations, several of which are capable of oxidizing H 2 . The Fe(I)Fe(I) species catalyze hydrogen evolution via the formation of iron hydrides. Catalysis is faster when the hydride is a terminal ligand, but also proceeds for isomeric species with a bridging hydride ligand. Models for [Fe]‐H 2 ases feature biomimetic coordination spheres consisting of acyl, thiolate, and 2‐substituted pyridine ligands bound to a redox‐inactive ferrous center.

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Ruthenium-catalyzed decarboxylation of 9-cisoctadecenoic is a path to produce biobased olefins. Here, a mechanistic study of this reaction was undertaken utilizing a closed reaction system and a pressure reactor. The proposed mechanism of an isomerization followed by a decarboxylation reaction was consistent with a mathematical kinetic model. That same model was able to accurately predict CO 2 evolution. Additionally, computational chemistry was used to determine that the barrier of the oleic acid decarboxylation reaction is 249 kJ mol −1 . Using the new information, the efficacy of the decarboxylation reaction was improved to an overall catalytic efficiency of 850 total turnovers.

Heavy-metal contamination is one of the most important environmental problems faced in the world, particularly in developing countries. Metals such as silver and mercury from drinking water, food, and air sources can accumulate in living organisms and present significant health concerns. Meanwhile, the demand for these metals in many industries continues to increase. In the present study, thioether-functionalized corn oil (TFCO) from a photoinitiated thiol-ene synthesis was utilized to remove Ag + and Hg 2+ ions from an aqueous solution. An aqueous solution containing AgNO 3 and Hg[NO 3 ] 2 was prepared and contacted directly with TFCO. After vortex mixing for 60 s, the experiment ran for 351 min with the aqueous phase being periodically sampled for the analysis of metal ions (M n+ ). Results showed that 88.9% of Ag + and 99.6% of Hg 2+ ions were removed from the aqueous phase by the TFCO. Mass balances indicated that the total M n+ concentration in the oil phase was 13.890 g kg −1 under the conditions studied. TFCO exhibited higher selectivity for removing Hg 2+ than for Ag + ions. Analysis of the adsorption kinetics showed that a pseudosecond-order model may be used to determine the rate of Ag + ion sorption by the oil phase. The presence of the Hg 2+ ions interfered with the adsorption of Ag + ions from the aqueous solution.Keywords Remediation Á Thioether-functionalized oil J Am Oil Chem Soc (2018) 95: 1189-1200. Abbreviations ICP-OESinductively coupled plasma-optical emission spectroscopy TFCO thioether-functionalized corn oil HPLC high performance liquid chromatography NMR nuclear magnetic resonance Symbols C 0 metal concentration in the aqueous phase before mixing with oil (mg kg −1 ) C e metal concentration in the aqueous phase at equilibrium (t ! ∞) (mg kg −1 )metal concentration in the aqueous phase at t (mg kg −1 ) k 2 pseudosecond-order adsorption rate constant (kg [mg min] −1 ) K D partition (distribution) coefficient at equilibrium (t ! ∞) m w mass of aqueous phase (g) M n+ metal ions m o mass of the TFCO phase (g) q [t] metal concentration in the oil phase at t (mg kg −1 ) q e metal concentration in the oil phase at equilibrium (t ! ∞) (mg kg −1 ) R 2 coefficient of correlation t time (min) σ y standard error of the y-estimate