Reduction of nitrite to nitric oxide and generation of reactive chalcogen species by mononuclear Fe(ii) and Zn(ii) complexes of thiolate and selenolate

Abstract

A comparative study of isostructural Zn(ii) and Fe(ii) compounds for their reactivity with nitrite, transfer of the coordinated thiolate/selenolate and generation and transfer of reactive sulfur/selenium species is presented.

Generation of Thiosulfate, Selenite, Dithiosulfite, Perthionitrite, Nitric Oxide, and Reactive Chalcogen Species by Binuclear Zinc(II)-Chalcogenolato/-Polychalcogenido Complexes

“…These results are in line with our previous report with mononuclear Zn(II)and Fe(II)-thiolate complexes where the use of [Se] in the place of S 8 in the above-mentioned reactions could not generate RSS/RSeS. 62 The present work coupled with our previous report thus indicates that [Se] is comparatively less efficient than S 8 for the generation of RSS/RSeS.…”

“…91 Complex 4b features two terminal benzeneselenolates with Zn−Se distances of 2.4554(11) Å and 2.4463(12) Å which are comparable with the Zn−Se distances reported previously for the complexes, [Zn(SePh) 4 ] 2− (av. Zn−Se = 2.469 Å), 93 [(Py2ald)Zn(SePh)] (2.4577(6) Å), 62 and [(py) 2 Zn-(SeC 6 F 5 ) 2 ] (2.4130(2) Å, 2.4175(3) Å; py = pyridine). The difference between the average Zn−Se (2.4508 Å in 4b) and Zn−S (2.3395 Å in 4a) distances is ∼0.11 Å, which is also consistent with the difference (0.15 Å) between the covalent radii of S (1.02 Å) and Se (1.17 Å).…”

“…62 In this work, 62 we reported that both the Fe(II) and Zn(II) compounds, [M(Py2ald)(SPh)] (M = Zn, Fe), were equally efficient for the generation of RSS upon treatment with S 8 and that this process was more efficient than the reaction of [M(Py2ald)(SePh)] (M = Zn, Fe) with S 8 for the generation of mixed sulfur−selenium species. 62 Therefore, in the present work, we have studied the generation of RSS/RSeS by the reaction of 1a, 1b, 4a and 4b with S 8 (Scheme 2) which allowed us to compare the effectiveness of the binuclear Zn(II)-monothiolate complexes (1a, 1b) and the binuclear Zn(II)-bis(thiolate/selenolate) complexes (4a, 4b) for the generation of RSS/RSeS vs the generation of disulfide/ diselenide (Table 1). Treatment of 1a with S 8 followed by the addition of PhCH 2 Br generated MeS-SCH 2 Ph as the major product.…”

“…In relation to this, Pluth and co-workers described the structure and reactivity of the dichalcogenides, RSS − , RSSe − , RSeS − and RSeSe − , 61 while we demonstrated the generation of RSS/RSeS by the reaction of mononuclear Zn(II)-thiolate/selenolate complexes and elemental sulfur/selenium. 62 Readily accessible oxidation states of -II to + VI for sulfur and selenium, biological implications of sulfur and selenium derived anions and the ability of these anions to bridge multiple metal centers have paved the way for the development of transition metals chemistry of S n 2− and Se n 2− ligands. While the synthetic methods reported in the literature for the generation of transition metal-polychalcogenido complexes mainly involved either the reaction of elemental chalcogens with low valent transition metals or the reaction of transition metal salts with S n 2− /Se n 2−…”

Synthesis, Characterization, and Reactivity of a Synthetic End-On Cobalt(II) Alkyl Persulfide Complex as a Model Platform for Thiolate Persulfidation

“…The wide redox availability of sulfur and highly complex interconversions between different RSS through both one- and two-electron mechanisms pose both opportunities and challenges for understanding the reactivity of RSS – . Despite the prevalence of RSS – in biology, synthetic systems of free RSS – anions or those ligated to metal centers are scarce due to the high lability of RSS – , which equilibrate with longer chain alkyl polysulfides (RSSS n – ), polysulfide radicals (S 3 •– ), and disulfides (R 2 S 2 ) in solution, further exacerbating modeling direct interactions between RSS – and transition metal centers. − In addition, direct generation of metal alkyl persulfides complexes from metal thiolates and elemental sulfur (S 8 ) remains a synthetic pathway with poor selectivity, often yielding transition metal alkyl polysulfides and one-electron oxidized transition metal polysulfides. , Reported transition metal persulfide complexes have primarily generated as side-products, and targeted syntheses are largely reliant on both the identities of metal centers and the associated primary coordination spheres. , To the best of our knowledge, there are only three structurally characterized mononuclear alkyl persulfide complexes of late first-row transition metals (Figure ). Kovacs and co-workers reported the first structurally characterized examples of late first-row transition metal η 2 -alkyl persulfide complexes [Fe III (S Me2 N 3 (Et,Pr)(η 2 -S 2 )][PF 6 ] through outer sphere oxidation of the corresponding thiolate complexes with FcPF 6 .…”