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The ultra‐alkaline conditions of a hydroflux offer the possibility of redox chemistry far from the electrochemical standard potentials. We explored the possibilities of synthesizing tellurium(VI) compounds, using both tellurium(VI) and tellurium(IV) as starting materials. Colorless, block‐shaped crystals of the oxohydroxotellurate(VI) K2[TeO2(OH)4] were synthesized from (NH4)2TeO4 in a KOH hydroflux at 200 °C. In the triclinic crystal structure, [TeO2(OH)4]2− octahedra are connected via hydrogen bonds to form layers, which are separated from each other by potassium cations. Yellow‐colored platelets of the ferrate(III) tellurate(VI) K2[Fe2TeO6(OH)2] ⋅ 2H2O were obtained by oxidation of TeO2 with H2O2 followed by reaction with Fe(NO3)3 ⋅ 9H2O in a KOH hydroflux. In the monoclinic crystal structure, strongly corrugated anionic layers ∞2[ ${{}_{\infty }{}^{2}[}$ Fe2TeO6(OH)2]2− are covered with water molecules and separated from each other by potassium cations. The octahedrally coordinated iron(III) atoms form a distorted honeycomb network, in which they are antiferromagnetically coupled at room temperature and in external fields up to at least 7 T. [ABSTRACT FROM AUTHOR]

Soluble tetrabutylammonium ferrates, [TBA][FeX 3 Y] (TBA = n Bu 4 N) were synthetized by treating ferric salts (FeX 3) with tetrabuthylammoniom halides. Their activity as a stand-alone catalyst in CO 2 cycloaddition reactions to epoxides was assessed under solvent free and quite mild reaction conditions (CO 2 pressures between 0.4 and 0.8 MPa) and TOF up to 428 h-1 (T = 150 °C) were observed. Good yields of cyclic organic carbonates were obtained, especially with terminal epoxides, without the need of any Lewis base as co-catalyst, with a broad reaction scope. A scale-up reaction on 5 mL of styrene oxide was performed and the robustness of the catalyst was proved up to three recycles in the case of propylene oxide (TON = 594). To shed light on the reaction mechanism, an extensive set of theoretical calculations has been carried out. Iron salts almost annihilate the barrier for the epoxide ring opening and stabilize the first reaction intermediate. Along the same reaction path, chloride proved to be more effective as nucleophile than bromide, and preferentially attacks on the more hindered carbon atom. On the other hand, when no Lewis acid (LA) is present, the rate determining step of the reaction becomes the ring opening of the epoxide. A tight correlation with experimental results was observed. Smart ammonium ferrates, [TBA][FeX 3 Y] , as stand-alone catalyst for the transformation of epoxides and CO 2 into cyclic organic carbonates. [Display omitted] • Very simple ammonium ferrates with activity in the CO 2 cycloaddition to epoxides. • No need for a co-catalyst (Lewis base). • High conversions and selectivities under solvent-free and quite mild reaction conditions. • TOF up to 428 h-1 and TONs up to 594. • An extensive set of theoretical calculations has been carried out highlighting the bifunctional nature of the catalyst. [ABSTRACT FROM AUTHOR]

A series of new potassium and rubidium sulfido ferrates were synthesized from iron and sulfur using elemental potassium and Rb2S as alkali element sources. The structures of all title compounds were determined by means of single-crystal X-ray data. Isolated ortho anions [FeIIIS4]5-, together with disulfide and sulfide anions, are the structure elements in K9[FeS4](S2)S (monoclinic, space group P21/ c, a = 1068.58(2), b = 787.480(10), c = 2372.96(3) pm, β = 102.9670(10)°, Z = 4, R1 = 0.0325). The diferrates A6[FeIII2S6], among which only the sodium and the cesium salts were known so far, contain dimers of two edge-sharing [FeS4] tetrahedra. The potassium and the monoclinic form of the rubidium compound (monoclinic, space group P21/ c, a = 772.50(1)/796.06(5), b = 1251.24(2)/1291.35(8), c = 1002.80(1)/1032.40(6) pm, β = 127.5260(10)/127.163(4), Z = 2, R1 = 0.0356/0.0466) crystallize with the Cs3GaSe3 structure type. The second, orthorhombic form of Rb6[FeIII2S6] is isotypic to the cesium ferrate (orthorhombic, space group Cmca, a = 1884.36(3), b = 695.660(10), c = 1296.09(2) pm, Z = 4, R1 = 0.0220) forming the Ba3AlSb3 structure type. The rubidium ferrate Rb8[Fe4S10] crystallizes with a new structure type (triclinic, space group P $\bar{1}$, a = 744.65(3), b = 851.21(3), c = 1042.77(4) pm, α = 77.990(2), β = 85.244(2) γ = 81.051(2)°, Z = 1, R1 = 0.0537). The structure exhibits novel tetrameres [Fe4S10]8- of edge-sharing tetrahedra, which represent segments of the well-known chain compounds A[FeS2]. K7[FeII/IIIS2]5 (monoclinic, space group C2/ c, a = 2790.1(3), b = 1153.74(13), c = 720.17(8) pm, β = 102.746(8)°, Z = 4, R1 = 0.0407) exhibits SiS2 analogous chains of edge-sharing [FeS4] tetrahedra and contains iron in oxidation states II and III in a 2:3 ratio. This compound is an interesting 'intermediate' inbetween the ferrate(III) K[FeIIIS2] and K3[FeII/IIIS2]2, with a 1:1 ratio of FeII:FeIII. [ABSTRACT FROM AUTHOR]

A series of new potassium and rubidium sulfido ferrates were synthesized from iron and sulfur using elemental potassium and Rb2S as alkali element sources. The structures of all title compounds were determined by means of single-crystal X-ray data. Isolated ortho anions [FeIIIS4]5-, together with disulfide and sulfide anions, are the structure elements in K9[FeS4](S2)S (monoclinic, space group P21/ c, a = 1068.58(2), b = 787.480(10), c = 2372.96(3) pm, β = 102.9670(10)°, Z = 4, R1 = 0.0325). The diferrates A6[FeIII2S6], among which only the sodium and the cesium salts were known so far, contain dimers of two edge-sharing [FeS4] tetrahedra. The potassium and the monoclinic form of the rubidium compound (monoclinic, space group P21/ c, a = 772.50(1)/796.06(5), b = 1251.24(2)/1291.35(8), c = 1002.80(1)/1032.40(6) pm, β = 127.5260(10)/127.163(4), Z = 2, R1 = 0.0356/0.0466) crystallize with the Cs3GaSe3 structure type. The second, orthorhombic form of Rb6[FeIII2S6] is isotypic to the cesium ferrate (orthorhombic, space group Cmca, a = 1884.36(3), b = 695.660(10), c = 1296.09(2) pm, Z = 4, R1 = 0.0220) forming the Ba3AlSb3 structure type. The rubidium ferrate Rb8[Fe4S10] crystallizes with a new structure type (triclinic, space group P $\bar{1}$, a = 744.65(3), b = 851.21(3), c = 1042.77(4) pm, α = 77.990(2), β = 85.244(2) γ = 81.051(2)°, Z = 1, R1 = 0.0537). The structure exhibits novel tetrameres [Fe4S10]8- of edge-sharing tetrahedra, which represent segments of the well-known chain compounds A[FeS2]. K7[FeII/IIIS2]5 (monoclinic, space group C2/ c, a = 2790.1(3), b = 1153.74(13), c = 720.17(8) pm, β = 102.746(8)°, Z = 4, R1 = 0.0407) exhibits SiS2 analogous chains of edge-sharing [FeS4] tetrahedra and contains iron in oxidation states II and III in a 2:3 ratio. This compound is an interesting 'intermediate' inbetween the ferrate(III) K[FeIIIS2] and K3[FeII/IIIS2]2, with a 1:1 ratio of FeII:FeIII. [ABSTRACT FROM AUTHOR]

Na5[FeO3][OH] has been obtained from a redox reaction between iron metal and CdO in the presence of Na2O and NaOH at 450 °C (5 d) as red crystals. The structure has been determined from single crystal data ( Pnma, Z = 8, a = 990.94(7) pm, b = 1016.41(7) pm, c = 1185.35(8) pm, wR2 = 0.050) and evaluated by MAPLE calculations. In addition, we present experimental single-crystal IR and Raman spectroscopic data to discuss aspects of the isolated [FeO3]4- complexes and non-coordinating hydroxide in comparison with the respective cobalt compounds. Additional ab-initio lattice dynamic calculations are included for comparison. [ABSTRACT FROM AUTHOR]