Recent advances in polyoxothiometalate chemistry

Figures & data

Figure 1. Structures of the three build blocks used in POTMs. a) [Mo^V₂O₂(µ-S)₂]²⁺, b) [W^V₂O₂(µ-S)₂]²⁺ and c) [Mo^IV₃(µ₃-S)(µ-S)]⁴⁺. Mo, teal; W, blue; O, red; S yellow; open coordination faces highlighted with translucent grey atoms.

Figure 2. Schematic representation of the self-condensation process of [Mo^V₂O₂(µ-S)₂(H₂O)₆]²⁺ as a result of increased pH.

Figure 3. Crystal structures of the POTM rings described in this section. A) {Mo₁₆(IsoP)₂}, {Mo₁₆(abtc)}, {Mo₁₆(abtc)₂}; B) {Mo₁₄(C₄O₄)₂}, {Mo₁₆(C₄O₄)₂K₂}, {Mo₁₂(AcO)₂}; C) {Mo₁₀}_n{thiophenediphosphonate}_n; D) {Mo₁₆(DFMT)}, {Mo₁₂(DMT)}. (IsoP = isopthalate, abtc = 3,5-dicarboxyl-(3’,5’-dicarboxyazophenyl), DFMT = 2,5-bis(trifluoro)methylterephthalate, DMT = 2,5-dimethylterephthalate). Formulas are given in shorthand for clarity. Mo, teal; N, blue; O, Red; P, purple; C, white; S, yellow; K, grey; F, green.

Figure 4. Crystal structures of the POTMs described in this section. A) {Mo₈S₈(Ale)₄}, {Mo₈S₈(Zol)₄}, {Mo₈O₈(Ale)₄}; B) {Mo₄(Tart)₂}; C) {Mo₂₀(PyD)₂}; D) {Mo^V₈S₈(Mo^VI₈)₄}; E) {W^VI₇₂Mo^V₆₀S₆₀}, {Mo^VI₇₂Mo^V₆₀S₆₀}; F) {(Mo^V₆S₆)₈(Mo^VI₃)₁₂}, {(Mo^VI₁₇)₃Mo^V₁₂S₆} (Ale = alendronic acid, Zol = zoledronic acid, Tart = tartarate (racemic), PyD = 3,5-pyridinedicarboxylic acid). Formulas are given in shorthand for clarity. Mo, teal (Mo^V, spheres, Mo^VI polyhedra); W, dark blue polyhedra, N, blue spheres, O, red; C, white; S, yellow; Rb, green; hydrogen omitted for clarity.

Figure 5. Building blocks used in squarate/molybdate system. A) [Mo^V₂O₂(µ-S)₂]²⁺, B) Squarate ([C₄O₄]^2–), C) Square-type building block, D) Diamond-type building block, E) [Mo^VI₂O₈]^4–, F) Lindqvist fragment [Mo^VI₅O₁₈]^6– top-down and side-on views, G) Pentagonal fragment [Mo^VI₆O₂₁]^5– top-down and side-on views. Mo, teal; O, red; S, yellow; C, white; coordination positions shown as translucent grey.

Figure 6. Squarate/[Mo^VI₂O₈]^4– system showing how the building blocks can assemble into A) {Mo^V₁₂(C₄O₄)₂(Mo^VI₂O₈)₂}, B) {Mo^V₈(C₄O₄)(Mo^VI₂O₈)} or C) {Mo^V₈(C₄O₄)(Mo^VIO₄)₂}. Mo, teal; O, red; S, yellow; C, white; coordination positions shown as translucent grey.

Figure 7. Squarate/[Mo^VI₅O₁₈]^6– system showing how the building blocks can assemble into A) {Mo^V₃₀(C₄O₄)₅(Mo^VI₅O₁₈)₃}, B) {Mo^V₃₂(C₄O₄)₅(Mo^VI₅O₁₈)₃}, C) {Mo^V₄₀(C₄O₄)₇(Mo^VI₅O₁₈)₃}, D) {Mo^V₆₆(C₄O₄)₁₂(Mo^VI₅O₁₈)₆} or E) {Mo^V₄₈(C₄O₄)₈(Mo^VI₅O₁₈)₄}. Mo, teal; O, red; S, yellow; C, white; Coordination positions shown as translucent grey. Red arrows indicate structural relationship and do not necessarily indicate reaction pathway.

Figure 8. Squarate/[Mo^VI(Mo^VI₅)O₂₁]^5– system and related systems with croconate. Colored circles represent the components present in the conditions that give the indicated product. A) {Mo^V₁₈(C₄O₄)₉}, B) {Mo^V₁₀(C₅O₅)}, C) {Mo^V₂(C₅O₅)} co-crystallized with {Mo^VI₁₂(C₄O₄)₄}, D) {Mo^V₃₆(C₄O₄)₄(Mo^VI(Mo^VI₅))₂}, E) {Mo^V₄₈(C₄O₄)₆(Mo^VI(Mo^VI₅))₂}, F) {Mo^V₄₈(C₄O₄)₆(Mo^VI(Mo^VI₅))₂} co-crystallized with {Mo^VI₁₂(C₄O₄)₄}. Mo, teal; O, red; S, yellow; C, white; coordination positions shown as translucent grey. Red arrows indicate structural relationship and do not necessarily indicate reaction pathway.

Figure 9. Reaction coordinates of the selenite POTM system. Structures are positioned according to relative relationship between pH and Se:Mo ratio required for formation. The position does not reflect exact pH or Se:Mo values. A) {Mo^V₂₇(SeO₃)₁₇}, B) {Mo^V₁₆(SeO₃)₂₀}, C) {Mo^V₁₆(SeO₃)} and D) {Mo^V₃₆(SeO₃)₆}. Mo, teal; O, red; S, yellow; C, white; Se, purple; coordination positions shown as translucent grey. Red arrows indicate structural relationship and do not necessarily indicate reaction pathway.

Figure 10. Structures mentioned in this section that do not belong to a specific system of building blocks. A) {Mo^V₁₂(SO₃)₁₆}, B) {Mo^V₁₂(W^VI₁₄Se₂O₅₂)₃}, C) {Mo^V₁₆(W^VI₁₄Se₂O₅₂)₅W^VI₂₂}. Mo, teal; W, blue polyhedra; O, red; S, yellow; C, white; Se, purple; coordination positions shown as translucent grey.

Figure 11. Combination of [Mo^V₂O₂(µ-S)₂]²⁺ and tellurite, with (bottom) and without (top) squarate. Colored circles show the building blocks that join to give the structures. A) {Mo^V₈(TeO₃)}, B) {Mo^V₂₄(TeO₃)}, C) {Mo^V₂₀(TeO₃)(Te₂(µ-O)₂O₄)(Te₂(µ-O)O₅)}, D) {Mo^V₂₄(C₄O₄)₄(TeO₄)₂}, E) {Mo^V₃₀(C₄O₄)₃(TeO₄)₃}, F) {Mo^V₂₈(C₄O₄)₄(TeO₄)₂} and G) {Mo^V₇₂(C₄O₄)₈(Te₃O₁₀)₄}. Mo, teal; O, red; S, yellow; C, white; Te, brown; Coordination positions shown as translucent grey. Red arrows indicate structural relationship and do not necessarily indicate reaction pathway.

Figure 12. POTM structures that have been used as HER electrocatalysts. A) [Mo^V₂O₂(µ-S)₂(S₂)₂]^2-, [Mo^V₂O₂(µ-S)₂(S₂)(S₄)]^2-, [W^V₂O₂(µ-S)₂(S₂)(S₄)]^2-, B) {Mo^V₈Ox}, {Mo^V₁₂BTC}, C) {Mo^V₂₀PyD₂}, {Mo₁₂Nap}, D) {Mo^V₈S₈Ale₄}, E) {Mo^V₁₈(Mo^IV₃S₄(nta)₃)}, {Mo^V₁₂(Ni(DTO)₂)}, F) {Mo₁₂TMT}, no crystal structure exists for {Mo₁₂DFMT} (Ox = oxalate, BTC = benzenetricarboxylate, PyD = 3,5-pyridinedicarboxylate, Nap = 1,4-napthalenedicarboxylate, Ale = alendronic acid, nta = nitrilotriacetate, DTO = dithiooxalate, TMT = tetramethylterephthalate, DFMT = di-trifluoromethylterephthalate). Mo, teal; N, blue; O, red; S, yellow; C, white; Rb, green; W, dark blue; hydrogen omitted for clarity.