Abstract Four new mixed-valent chain alkali metal (A) sulfido ferrates of the general structure family A 1 + x Fe x II Fe 1 − x III S 2 ${A}_{1+x}\left[{\text{Fe}}_{x}^{\text{II}}{\text{Fe}}_{1-x}^{\text{III}}{\text{S}}_{2}\right]$ were synthesized in the form of tiny green-metallic needles from nearly stoichiometric melts reacting elemental potassium with natural pyrite (A = K) or previously prepared Rb2S/Cs2S2 with elemental iron and sulfur (A = Rb/Cs). The crystal structures of the compounds were determined by means of single crystal X-ray diffraction: In the (3+1)D modulated structure of K7.15[FeS2]4 (space group Ccce(00σ 3)0s0, a = 1363.87(5), b = 2487.23(13), c = 583.47(3) pm, q = 0,0,0.444, R1 = 0.055/0.148, x = 0.787), a position modulation of the two crystallographically different undulated [ FeS 4 / 2 ] ∞ 1 ${}_{\infty }{}^{1}\left[{\text{FeS}}_{4/2}\right]$ tetrahedra chains and the surrounding K cations is associated with an occupation modulation of one of the three potassium sites. In the case of the new monoclinic rubidium ferrate Rb4[FeS2]3 (x = 1 3 $\frac{1}{3}$ ; space group P21/c, a = 1640.49(12), b = 1191.94(9), c = 743.33(6) pm, β = 94.759(4)°, Z = 4, R1 = 0.1184) the undulation of the tetrahedra chain is commensurate, the repetition unit consists of six tetrahedra. In the second new Rb ferrate, Rb7[FeS2]5 (x = 0.4; monoclinic, space group C2/c, K7[FeS2]5-type; a = 2833.9(2), b = 1197.36(9), c = 744.63(6) pm, β = 103.233(4)°, Z = 4, R1 = 0.1474) and its isotypic mixed Rb/Cs-analog Rb3.6Cs3.4[FeS2]5 (a = 2843.57(5), b = 1226.47(2), c = 759.890(10) pm, β = 103.7170(9)°, R1 = 0.0376) the chain buckling leads to a further increased repetition unit of 10 tetrahedra. For all mixed-valent ferrates, the Fe–S bond lengths continuously increase with the amount (x) of Fe(II). The buckling of the chains is controlled through the local coordination of the S atoms by the variable number of A cations of different sizes.

中文翻译：

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新的混合价碱链硫基高铁酸盐 A1+x[FeS2] (A = K, Rb, Cs; x = 0.333–0.787)

摘要 一般结构族 A 1 + x Fe x II Fe 1 − x III S 2 ${A}_{1+x}\left[{\text{ Fe}}_{x}^{\text{II}}{\text{Fe}}_{1-x}^{\text{III}}{\text{S}}_{2}\right] $ 是以微小的绿色金属针的形式由元素钾与天然黄铁矿 (A = K) 或先前制备的 Rb2S/Cs2S2 与元素铁和硫 (A = Rb/Cs) 反应的化学计量熔体合成的。通过单晶X射线衍射确定了化合物的晶体结构：在K7.15[FeS2]4的(3+1)D调制结构(空间群Ccce(00σ 3)0s0，a = 1363.87( 5), b = 2487.23(13), c = 583.47(3) pm, q = 0,0,0.444, R1 = 0.055/0.148, x = 0.787), 两个晶体学不同的波动 [ FeS 4 / 2 ] ∞ 1 ${}_{\infty }{}^{1}\left[{\text{FeS}}_{4/2}\right] 的位置调制$四面体链和周围的钾离子与三个钾位点之一的占领调节有关。对于新的单斜晶高铁酸铷 Rb4[FeS2]3 (x = 1 3 $\frac{1}{3}$ ; 空间群 P21/c, a = 1640.49(12), b = 1191.94(9), c = 743.33(6) pm, β = 94.759(4)°, Z = 4, R1 = 0.1184) 四面体链的起伏是相称的，重复单元由六个四面体组成。在第二个新的高铁酸盐 Rb 中，Rb7[FeS2]5 (x = 0.4；单斜晶系，空间群 C2/c，K7[FeS2]5 型；a = 2833.9(2)，b = 1197.36(9)，c = 744.63 (6) pm, β = 103.233(4)°, Z = 4, R1 = 0.1474) 及其同型混合 Rb/Cs-类似物 Rb3.6Cs3.4[FeS2]5 (a = 2843.57(5), b = 1226.47 (2), c = 759.890(10) pm, β = 103.7170(9)°, R1 = 0.0376) 链屈曲导致 10 个四面体的重复单位进一步增加。对于所有混合价高铁酸盐，Fe-S 键长随着 Fe(II) 的量 (x) 不断增加。链的屈曲是通过 S 原子的局部配位由不同数量的不同大小的 A 阳离子控制的。