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A new mononuclear cobalt(III)-pentasulfido compound, [(L)Co(S 5 )] (3) has been synthesized by using a convergent redox reaction between elemental sulfur and two new cobalt(II)-thiolato compounds, [(L)Co(SR)] (R=Ph, 2 a; 2,6-Me 2 -C 6 H 4 , 2 b), which in turn were synthesized from a dimeric cobalt(II) complex, [(L) 2 Co 2 ] 2+ (1). Compound 3 features a low-spin, diamagnetic, Co(III) center with a coordinated pentasulfido (S 5 2- ) chain and has no precedence in the literature. Compound 3 is highly stable towards reduction with a potential of -1.36 V (vs. Cp 2 Fe + /Cp 2 chain in 3 leads to the formation of 1, elemental sulfur and H 5 2- chain in 3 leads to the formation of 1, elemental sulfur and H 2 S. Finally, transfer of the coordinated S 5 2- chain in 3 to selected organic compounds, such as MeI, PhCH 2 Br and PhCOCl, for the generation of organopolysulfido compounds has been demonstrated., (© 2023 Wiley-VCH GmbH.)

Reactions directed at the synthesis of structural analogues of the active site of molybdenum-containing carbon monoxide dehydrogenase have been investigated utilizing [WO(2)S(bdt)](2-) (1) and [WOS(2)(bdt)](2-) (2) and sterically hindered [Cu(R)L] or [Cu(SSiR'(3))(2)](-) as reactants. All successful reactions of 2 afford the binuclear W(VI)/Cu(I) products [WO(bdt)(mu(2)-S)(2)Cu(L)](2-/-) with L = carbene (3), Ar*S (4), Ar* (7), SSiR(3) (R = Ph (5), Pr(i) (6)). Similarly, [W(bdt)(OSiPh(3))S(2)](-) leads to [W(bdt)(OSiPh(3))(mu(2)-S)(2)Cu(SAr*)](-) (8). These complexes, with apical oxo and basal dithiolato and sulfido coordination (excluding 8), terminal thiolate ligation at Cu(I) (4-6, 8), and W-(mu(2)-S)-Cu bridging, bear a structural resemblance to the enzyme site. Differences include two bridges instead of one and the absence of basal oxo/hydroxo ligation. Complex 8 differs from the others by utilizing apical and basal sulfido ligands in bridge formation. Related reaction systems based on 1 gave 4 in small yield or product mixtures in which the desired monobridged complex [WO(2)(bdt)(mu(2)-S)Cu(R)](2-) was not detected. Mass spectrometric analysis of the reaction system with L = carbene suggests that any monobridged species forms may converted to the dibridged form by disproportionation. In these experiments, the use of W(VI) preserves the structural integrity of Mo(VI), whose analogues of 1 and 2 have not been isolated. (Ar* = 2,6-bis(2,4,6-triisopropylphenyl)phenyl, bdt = benzene-1,2-dithiolate(2-)).

Comparative reactivity of a series of new Zn(II) and Fe(II) compounds, [(Py2ald)M(ER)] (E = S, R = Ph: M = Zn, 1aZn; M = Fe, 1aFe; E = S, R = 2,6-Me2-C6H3: M = Zn, 1bZn; M = Fe, 1bFe; E = Se, R = Ph: M = Zn, 2Zn; M = Fe, 2Fe), and [(Py2ald)M]22+ (M = Zn, 5Zn; M = Fe, 5Fe) is presented. Compound 1aZn could react with nitrite (NO2−) to produce [(Py2ald)Zn(ONO)] (3Zn), which, upon treatment with thiols and PhSeH (proton source), could regenerate either 1aZn/5Zn and 2Zn respectively, along with the production of nitric oxide (NO) where the yield of NO increases in the order tBuSH ≪ PhCH2SH < PhSH < PhSeH. In contrast to this, 1aFe, 2Fe and 5Fe could affect the direct reduction of NO2− in the absence of protons to generate NO and [{(Py2ald)(ONO)Fe}2-μ2-O] (8Fe). Moreover, 8Fe could regenerate 5Fe and 1aFe/2Fe upon treatment with 4 and 6 equiv. of PhEH (E = S/Se), respectively, along with the generation of NO. Finally, a comparative study of the mononuclear Zn(II) and Fe(II) compounds for the transfer of the coordinated thiolate/selenolate and the generation and transfer of reactive sulfur/selenium species (RES−, E = Se, S) to a series of organic substrates has been provided. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a series of new binuclear Zn(II) complexes bearing (i) terminal H2O/OH, (ii) bridging thiolates, (iii) bridging thiocarboxylates, (iv) bridging carboxylates, and (v) bridging carboxylate bearing free thiol groups are presented. Unlike the previously reported Co(II) and Fe(II) mediated desulfurization of thiolates to yield binuclear Co(II)/Fe(II)-hydrosulfide complexes by us (Jana et al., Inorg. Chem., 2018, 57, 617; Pal et al., Dalton Trans., 2019, 48, 5903), Zn(II) was found to be incapable of mediating the C–S bond cleavage of thiolates and thus allowed the isolation of binuclear Zn(II)–thiolate complexes. These binuclear Zn(II)–thiolate complexes were further examined for chemical oxidation of the coordinated thiolates and insertion of neutral sulfur into the Zn(II)–thiolate bonds. Interestingly, the latter reactivity study demonstrated the formation of a new binuclear Zn(II) complex featuring a bridging S32− unit which was generated via a redox reaction involving the bridging thiolates and the externally added elemental sulfur. [ABSTRACT FROM AUTHOR]

An extensive series of heterometal-iron-sulfur single cubane-type clusters with core oxidation levels [MFe3S3Q]3+,2+ (M = Mo, W; Q = S, Se) has been prepared by means of a new method of cluster self-assembly. The procedure utilizes the assembly system [(tBu3tach)MVIS3]/FeCl2/Na2Q/NaSR in acetonitrile/THF and affords product clusters in 30-50% yield. The trisulfido precursor acts as a template, binding FeII under reducing conditions and supplying the MS3 unit of the product. The system leads to specific incorporation of a μ3-chalcogenide from an external source (Na2Q) and affords the products [(tBu3tach)MFe3S3QL3]0/1- (L = Cl-, RS-), among which are the first MFe3S3Se clusters prepared. Some 16 clusters have been prepared, 13 of which have been characterized by X-ray structure determinations including the incomplete cubane [(tBu3tach)MoFe2S3Cl2(μ2-SPh)], a possible trapped intermediate in the assembly process. Comparisons of structural and electronic features of clusters differing only in atom Q at one cubane vertex are provided. In comparative pairs of complexes differing only in Q, placement of one selenide atom in the core increases core volumes by about 2% over the Q = S case, sets the order Q = Se > S in Fe-Q bond lengths and Q = S > Se in Fe-Q-Fe bond angles, causes small positive shifts in redox potentials, and has an essentially nil effect on 57Fe isomer shifts. Iron mean oxidation states and charge distributions are assigned to most clusters from isomer shifts. (tBu3tach = 1,3,5-tert-butyl-1,3,5-triazacyclohexane) [ABSTRACT FROM AUTHOR]