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A comparative bioinspired reactivity study of new binuclear Zn(II) complexes featuring coordinated thiolate, selenolate, trisulfide and diselenide in relation with (i) the generation of reactive sulfur/selenium species (RSS/RSeS), (ii) the oxygen dependent oxidation and disproportionation of polysulfide (Sn2–) to produce sulfite (SO32–), thiosulfate (S2O32–) and sulfide (S2–) by sulfur oxygenase reductase (SOR), and (iii) the reaction of Sn2–with nitrite (NO2–) to generate thionitrite (SNO–), perthionitrite (SSNO–) and nitric oxide (NO), is presented. The binuclear Zn(II)-thiolate/selenolate complexes could react with elemental sulfur to generate RSS/RSeS while similar reactions involving elemental selenium could not generate RSeS. The dizinc(II)-S3and the dizinc(II)-Se2complexes could react with dioxygen (O2) to generate binuclear Zn(II) complexes featuring coordinated thiosulfate (S2O32–) and selenite (SeO32–), respectively. Finally, unlike the nonreactive nature of the dizinc(II)-Se2complex toward NO2–, reaction of the dizinc(II)-S3complex with NO2–produced a new binuclear Zn(II) complex featuring a coordinated dithiosulfite (S3O2–) along with the formation of perthionitrite (SSNO–), of which the latter subsequently produced nitric oxide (NO) and S42–. The present work, thus, demonstrates the comparative reactivity of a series of binuclear Zn(II)-chalcogenolato/-polychalcogenido complexes for the generation of S2O32–, SeO32–, S3O2–, SSNO–, NO and RSS/RSeS.

Synthesis, characterization, electronic structure, and redox reactions of a mononuclear {FeNO}7complex with a very high N–O stretching frequency in solution are presented. Nitrosylation of [(LKP)Fe(DMF)]2+(1) (LKP= tris((1-methyl-4,5-diphenyl-1H-imidazol-2-yl)methyl)amine) produced a five-coordinate {FeNO}7complex, [(LKP)Fe(NO)]2+(2). While complex 2could accommodate an additional water molecule to generate a six-coordinate {FeNO}7complex, [(LKP)Fe(NO)(H2O)]2+(3), the coordinated H2O in 3dissociates to generate 2in solution. The molecular structure of 2features a nearly linear Fe–N–O unit with an Fe–N distance of 1.744(4) Å, N–O distance of 1.162(5) Å, and

Artificial intelligence (AI) has the potential for vast societal and economic gain; yet applications are developed in a largely ad hoc manner, lacking coherent, standardized, modular, and reusable infrastructures. The NSF‐funded Intelligent CyberInfrastructure with Computational Learning in the Environment AI Institute (“ICICLE”) aims to fundamentally advance edge‐to‐center, AI‐as‐a‐Service, achieved through intelligent cyberinfrastructure (CI) that spans the edge‐cloud‐HPC computing continuum, plug‐and‐playnext‐generation AI and intelligent CI services, and a commitment to design for broad accessibility and widespread benefit. This design is foundational to the institute's commitment to democratizing AI. The institute's CI activities are informed by three high‐impact domains: animal ecology, digital agriculture, and smart foodsheds. The institute's workforce development and broadening participation in computing efforts reinforce the institute's commitment to democratizing AI. ICICLE seeks to serve as the national nexus for AI and intelligent CI, and welcomes engagement across its wide set of programs.

A series of six binuclear Co(II)–thiolate complexes, [Co2(BPMP)(S–C6H4-o-X)2]1+(X = OMe, 2; NH2, 3), [Co2(BPMP)(μ-S–C6H4-o-O)]1+(4), and [Co2(BPMP)(μ-Y)]1+(Y = bdt, 5; tdt, 6; mnt, 7), has been synthesized from [Co2(BPMP)(MeOH)2(Cl)2]1+(1a) and [Co2(BPMP)(Cl)2]1+(1b), where BPMP1–is the anion of 2,6-bis[[bis(2-pyridylmethyl)amino]methyl]-4-methylphenol. While 2and 3could allow the two-electron redox reaction of the two coordinated thiolates with elemental sulfur (S8) to generate [Co2(BPMP)(μ-S5)]1+(8), the complexes, 4–7, could not undergo a similar reaction. An analogous redox reaction of 2with elemental selenium ([Se]) produced [{Co2(BPMP)(μ-Se4)}{Co2(BPMP)(μ-Se3)}]2+(9a) and [Co2(BPMP)(μ-Se4)]1+(9b). Further reaction of these polychalcogenido complexes, 8and 9a/9b, with PPh3allowed the isolation of [Co2(BPMP)(μ-S)]1+(10) and [Co2(BPMP)(μ-Se2)]1+(11), which, in turn, could be converted back to 8and 9aupon treatment with S8and [Se], respectively. Interestingly, while the redox reaction of the polyselenide chains in 9aand 11with S8produced 8and [Se], the treatment of 8with [Se] gave back only the starting material (8), thus demonstrating the different redox behavior of sulfur and selenium. Furthermore, the reaction of 8and 9a/9bwith activated alkynes and cyanide (CN–) allowed the isolation of the complexes, [Co2(BPMP)(μ-E2C2(CO2R)2)]1+(E = S: 12a, R = Me; 12b, R = Et; E = Se: 13a, R = Me; 13b, R = Et) and [Co2(BPMP)(μ-SH)(NCS)2] (14), respectively. The present work, thus, provides an interesting synthetic strategy, interconversions, and detailed comparative reactivity of binuclear Co(II)–polychalcogenido complexes.

Flavodiiron nitric oxide reductases (FNORs) protect microbes from nitrosative stress under anaerobic conditions by mediating the reduction of nitric oxide (NO) to nitrous oxide (N2O). The proposed mechanism for the catalytic reduction of NO by FNORs involves a dinitrosyldiiron intermediate with a [hs-{FeNO}7]2formulation, which produces N2O and a diferric species. Moreover, both NO and hydrogen sulfide (H2S) have been implicated in several similar physiological functions in biology and are also known to cross paths in cell signaling. Here we report the synthesis, spectroscopic and theoretical characterization, and N2O production activity of an unprecedented monohydrosulfidodinitrosyldiiron compound, with a [(HS)hs-{FeNO}7/hs-{FeNO}7] formulation, that models the key dinitrosyl intermediate of FNORs. The generation of N2O from this unique compound follows a semireduced pathway, where one-electron reduction generates a reactive hs-{FeNO}8center via the occupation of an Fe–NO antibonding orbital. In contrast to the well-known reactivity of H2S and NO, the coordinated hydrosulfide remains unreactive toward NO and acts only as a spectator ligand during the NO reduction process.

A detailed study for the synthesis of dinickel(II)–thiolate and dinickel(II)–hydrosulfide complexes and the complete characterization of the relevant intermediates involved in the C–S bond cleavage of thiolates are presented. Hydrated Ni(II) salts mediate the hydrolytic C–S bond cleavage of thiolates (NaSR/RSH; R = Me, Et, nBu, tBu), albeit inefficiently, to yield a mixture of a dinickel(II)–hydrosulfide complex, [Ni2(BPMP)(μ-SH)(DMF)2]2+(1), and the corresponding dinickel(II)–thiolate complexes, such as [Ni2(BPMP)(μ-SEt)(ClO4)]1+(2) (HBPMP is 2,6-bis[[bis(2-pyridylmethyl)amino]methyl]-4-methylphenol). A systematic study for the reactivity of thiolates with Ni(II) was therefore pursued which finally yielded 1as a pure product which has been characterized in comparison with the dinickel(II)–dichloride complex, [Ni2(BPMP)(Cl)2(MeOH)2]1+(3). While the reaction of thiolates with anhydrous Ni(OTf)2in dry conditions could only yield [Ni2(BPMP)(OTf)2]1+(5) instead of the expected dinickel(II)–thiolate compound, the C–S bond cleavage could be suppressed by the use of a chelating thiol, such as PhCOSH, to yield [Ni2(BPMP)(SCOPh)2]1+(6). Finally, with the suitable choice of a monodentate thiol, a dinickel(II)–monothiolate complex, [Ni2(BPMP)(SPh)(DMF)(MeOH)(H2O)]2+(7), was isolated as a pure product within 1 h of reaction, which after a longer time of reaction yielded 1and PhOH. Complex 7may thus be regarded as the intermediate that precedes the C–S bond cleavage and is generated by the reaction of a thiolate with an initially formed dinickel(II)–solvento complex, [Ni2(BPMP)(MeOH)2(H2O)2]3+(4). Selected dinickel(II) complexes were explored further for the scope of substitution reactions, and the results include the isolation of a dinickel(II)–bis(thiolate) complex, [Ni2(BPMP)(μ-SPh)2]1+(8).

The reduction of NO to N2O by flavodiiron nitric oxide reductases (FNORs) is related to the disruption of the defense mechanism in mammals against invading pathogens. The proposed mechanism for this catalytic reaction involves both nonheme mono- and dinitrosyl diiron(II) species as the key intermediates. Recently, we reported an initial account for NO reduction activity of an unprecedented mononitrosyl diiron(II) complex, [Fe2(N-Et-HPTB)(NO)(DMF)3](BF4)3(1) (N-Et-HPTB is the anion of N,N,N′,N′-tetrakis(2-(l-ethylbenzimidazolyl))-2-hydroxy-1,3-diaminopropane; DMF = dimethylformamide) with [FeII{FeNO}7] formulation [Jana et al. J. Am. Chem. Soc.2017, 139, 14380]. Here we report the full account for the selective synthesis, characterization, and reactivity of FNOR model complexes, which include a dinitrosyl diiron(II) complex, [Fe2(N-Et-HPTB)(NO)2(DMF)2](BF4)3(2) with [{FeNO}7]2formulation and a related, mixed-valent diiron(II, III) complex, [Fe2(N-Et-HPTB)(OH)(DMF)3](BF4)3(3). Importantly, whereas complex 2is able to produce 89% of N2O via a semireduced mechanism (1 equiv of CoCp2per dimer = 50% of NO reduced), complex 1, under the same conditions (0.5 equiv of CoCp2per dimer = 50% of NO reduced), generates only ∼50% of N2O. The mononitrosyl complex therefore requires superreduction for quantitative N2O generation, which constitutes an interesting dichotomy between 1and 2. Reaction products obtained after N2O generation by 2using 1 and 2 equiv of reductant were characterized by molecular structure determination and electron paramagnetic resonance spectroscopy. Despite several available literature reports on N2O generation by diiron complexes, this is the first case where the end products from these reactions could be characterized unambiguously, which clarifies a number of tantalizing observations about the nature of these products in the literature.

A unique Co(II)- and Fe(II)-mediated complete desulfurization of disulfides of the type RS-SR and RC(O)S-SC(O)R to yield the corresponding alcohols (ROH) and carboxylic acids (RCOOH), respectively, along with the formation of a dicobalt(II)/diiron(II)–hydrosulfide complex, [M2(PhBIMP)(μ2-SH)(DMF)]2+(M = Co, Fe), has been demonstrated. This new desulfurization reaction involves cleavage of both C–S and S–S bonds, where the cleavage of the S–S bond (presumably two-electron reduction of the S–S bond) may generate two-electron-oxidized dicobalt(III)/diiron(III) species, [MIII2(PhBIMP)(H2O)2(DMF)2]5+(M = Co, Fe), in solution. While the generation of such a solvent- and/or H2O-coordinated dicobalt(III) species in the reaction solution could not be established beyond a doubt, formation of the diiron(III) species [FeIII2(PhBIMP)(H2O)2(DMF)2]5+according to the proposed reaction mechanism has been confirmed by a combination of mass spectrometry and UV–vis spectroscopy in comparison with an authentic sample, synthesized directly by an independent procedure using Fe(ClO4)3·xH2O. Interestingly, a comparative study using different types of disulfides and the molecular structure determination of a key reaction intermediate, [Fe2(PhBIMP)(MeCOSS)]2+, generated via the cleavage of only one C–S bond of MeC(O)S-SC(O)Me, demonstrates that the C–S bond cleavage step precedes the S–S bond cleavage step during the Fe(II)-mediated desulfurization of disulfides.

A reaction system involving Fe(BF4)2·6H2O and two dinucleating ligands, HBPMP and HPhBIMP, mediates the desulfurization of aliphatic and aromatic thiols at room temperature. This rare C–S bond cleavage reaction produces two nonheme diiron(II) complexes, [Fe2(BPMP)(SH)2(MeOH)2]1+(1a) and [Fe2(PhBIMP)(μ-SH)(DMF)]2+(2a), possibly via an active species similar to [Fe2(PhBIMP)(H2O)2(DMF)2]3+(2c), while the thiols are converted to the corresponding alcohols/phenols. In the case of thioacetic acid, a bidentate chelating organosulfur substrate, the use of HBPMP produces the corresponding bis-thiocarboxylato bridged complex, [Fe2(BPMP)(CH3COS)2]1+(1b), instead of 1a. However, the use of HPhBIMP allows the Fe(II) mediated desulfurization of thioacetic acid as well to yield 2a, along with the formation of [Fe2(PhBIMP)(CH3COS)(MeCN)]2+(2b). This convenient desulfurization reaction has been demonstrated for different substrates in different solvents along with the structural and spectroscopic characterizations of the diiron(II)-hydrosulfide complexes in comparison with two isostructural chloride complexes, [Fe2(BPMP)(Cl)2(MeOH)2]1+(1c) and [Fe2(PhBIMP)(μ-Cl)(DMF)]2+(2d). The role of the individual reactants in the desulfurization process has been thoroughly investigated using control reactions, and on the basis of these results and the identification of intermediate species, such as [Fe2(PhBIMP)(StBu)(DMF)3]2+and [Fe2(PhBIMP)(StBu)(H2O)(DMF)2]2+, in solution by mass spectrometry, a possible mechanism has been proposed.

Desulfurization of organosulfur compounds is a highly important reaction because of its relevance to the hydrodesulfurization (HDS) process of fossil fuels. A reaction system involving Co(BF4)2·6H2O and the dinucleating ligands HBPMP or HPhBIMP has been developed that could desulfurize a large number of thiophenes, sulfides, and thiols to generate the complexes [Co2(BPMP)(μ2-SH)(MeCN)](BF4)2(1a), [Co2(BPMP)(SH)2](BF4) (1b), and [Co2(PhBIMP)(μ2-SH)(X)](BF4)2[X = DMF (2a), MeCN (2c)], while the substrates are mostly converted to the corresponding alcohols/phenols. This convenient desulfurization process has been demonstrated for 25 substrates in 6 different solvents at room temperature.

Synthesis and reactivity of a series of thiolate/thiocarboxylate bridged dicobalt(II) complexes were investigated in comparison with their carboxylate bridged analogues bearing free thiol/hydroxyl groups. Upon one-electron oxidation, complexes [Co2(N-Et-HPTB)(μ-SR1)](BF4)2(R1= Ph, 1a; Et, 1b; Py, 1c) and [Co2(N-Et-HPTB)(μ-SCOR2)](BF4)2(R2= Ph, 2a; Me, 2b) yielded [Co2(N-Et-HPTB)(DMF)2](BF4)3(6) (DMF = dimethylformamide) along with the corresponding disulfides (where N-Et-HPTB is the anion of N,N,N′,N′-tetrakis[2-(1-ethylbenzimidazolyl)]-2-hydroxy-1,3-diaminopropane). Unlike the inertness of carboxylate bridged complexes [Co2(N-Et-HPTB)(μ-O2C-R3-SH)](BF4)2(R3= Ph, 3a; CH2CH2, 3b) and [Co2(N-Et-HPTB)(μ-O2CR4)](BF4)2(R4= Ph, 4a; Me, 4b; CH2CH2CH2OH, 5) toward O2, the bridging ethanethiolate in 1bwas oxidized to yield a sulfinate bridged complex, [Co2(N-Et-HPTB)(μ-O2SEt)](BF4)2(10). Detailed investigation of the synthetic aspects of 1a–1cled to the discovery of a C–S bond cleavage reaction and yielded the dicobalt(II) complexes [Co2(N-Et-HPTB)(SH)(H2O)](BF4)2(8a), [Co2(N-CH2Py-HPTB)(SH)(H2O)](BF4)2(8b) (where N-CH2Py-HPTB is the anion of N,N,N′,N′-tetrakis[2-(1-picolylbenzimidazolyl)]-2-hydroxy-1,3-diaminopropane)), and [Co2(N-Et-HPTB)(μ-S)](BF4) (9). Both 8aand 8bfeature nonheme dinuclear Co(II) units containing a terminal hydrosulfide. The present study thus reports comparative redox reactions for a rare class of 16 dicobalt(II) complexes and introduces a selective synthetic strategy for the synthesis of unprecedented dicobalt(II) complexes featuring only one terminal hydrosulfide.

A new binuclear Zn(II) complex, [Zn2(PhBIMP)(DMF)2]3+(1) (where PhBIMP1is the anion of 2,6-bis[bis[(N-1-methyl-4,5-diphenylimidazoylmethyl)amino]methyl]-4-methylphenol), has been shown for the first time to mediate the hydrolytic C–S bond cleavage of a series of aliphatic and aromatic thiolates to yield the corresponding alcohols/phenols along with the formation of a hydrosulfide-bridged complex, [Zn2(PhBIMP)(μ-SH)(DMF)]2+(2), which has been thoroughly characterized in comparison with the corresponding chloride complex, [Zn2(PhBIMP)(Cl)(DMF)]2+(3), as a control. The binuclear Zn(II)-thiolate complexes [Zn2(PhBIMP)(μ-SR)]2+(R = Ph, 4a; 3-Br-C6H4, 4b) have also been synthesized by avoiding the C–S bond cleavage reaction. Based on the experimental results for the effects of H2O and Et3N on 1, 4a, and 4b, the complex [Zn2(PhBIMP)(μ-SR)(OH)]1+has been proposed to be the active intermediate that precedes the C–S bond cleavage of thiolates. The complex [Zn2(PhBIMP)(μ-SCOPh)(DMF)]2+(5) also demonstrates the hydrolysis of the coordinated thiobenzoate to produce [Zn2(PhBIMP)(μ-O2CPh)(MeCN)]2+(6). However, unlike 4aand 5, the benzeneselenolate-bridged complex, [Zn2(PhBIMP)(μ-SePh)]2+(7), does not generate the species, [Zn2(PhBIMP)(μ-SePh)(OH)]1+, in solution, and in line with that, the coordinated benzeneselenolate in 7does not undergo hydrolysis to generate hydroselenide and phenol. Finally, a comparative study for the transfer reactivity of the bridging –SH, –SPh, –SC(O)Ph, and –SePh ligands in 2, 4a, 5, and 7, respectively, toward selected organic substrates has been performed to reveal the distinct differences in the reactivity of these bridging ligands.

A new and efficient catalytic hydrolysis of aliphatic and aromatic thiolates under ambient conditions is presented. Previously, we have demonstrated (Ganguly et al., Inorg. Chem. 2018, 57, 11306–11309) the Co(II) mediated stoichiometric hydrolysis of thiols to produce alcohols/phenols along with a binuclear dicobalt(II)-hydrosulfide complex, [Co2(PhBIMP)(μ2-SH)(DMF)]2+(1) (PhBIMP is the anion of 2,6 bis[(bis((N-1-methyl-4,5- diphenylimidazoylmethyl) amino)methyl]- 4-methylphenol). In the present work, we have shown that the product of the stoichiometric reaction, 1, may act as an efficient catalyst for the catalytic hydrolysis of a broad range of aliphatic and aromatic thiolates in DMF at room temperature to produce alcohols/phenols. Complex 1takes up a thiolate (RS–) and a water molecule to generate an active intermediate complex, [Co2(PhBIMP)(μ2-SH)(RS)(H2O)]1+(2), which, in turn, releases the alcohol/phenol (ROH), hydrosulfide (HS–), and regenerates 1.

The synthesis and a detailed reactivity study of a binuclear zinc(II) bis(benzenethiolate) complex, [Zn2(BPMP)(SPh)2]+(4), and an unprecedented binuclear zinc(II) pentasulfido complex, [Zn2(BPMP)(μ2-S5)]+(6), are presented. While one-electron oxidation of the coordinated benzenethiolate ligands in 4by Cp2Fe+produces diphenyl disulfide and [Zn2(BPMP)(μ2-OH)]2+(5), a two-electron redox reaction between coordinated benzenethiolate ligands in 4and elemental S (S8) generated diphenyl disulfide and the binuclear zinc(II) pentasulfido complex 6. Complex 6features a chelating, dianionic, pentasulfido (S52–) chain and can consume up to a maximum of 3 equiv of PPh3to generate Ph3PS and 5, while the reaction of 6with 1 equiv of diphenylphosphinoethane allowed the isolation of [Zn2(BPMP)(μ2-S4)]+(7). A proteolysis reaction of the coordinated S52–chain in 6with fluoroboric acid (HBF4), benzoic acid (PhCOOH), and thioacetic acid (MeCOSH) generates the complexes [Zn2(BPMP)(MeCN)2]3+(1), [Zn2(BPMP)(μ2-PhCOO)2]+(8), and [Zn2(BPMP)(μ2-SCOMe)2]+(9), respectively, while the protonated S52–chain liberates S8and hydrogen sulfide (H2S). Finally, the transfer of the coordinated benzenethiolate ligands in 4and the S52–chain in 6to selected organic compounds, namely, PhCH2Br and PhC(O)Cl, for the generation of various organosulfur compounds is demonstrated.