The stannides Ca1.692Pt2Sn3.308, SrPtSn2 and EuAuSn2

Polycrystalline samples of the stannides Ca1.692Pt2Sn3.308, SrPtSn2 and EuAuSn2 were synthesized directly from the elements, using sealed tantalum ampoules as crucible material. The reactions were performed in muffle or induction furnaces. The phase purity of the samples was studied by X-ray powder diffraction (Guinier technique). The structures of Ca1.692Pt2Sn3.308 and SrPtSn2 were refined from single-crystal X-ray diffractometer data: NdRh2Sn4 type, Pnma, a = 1887.22(13), b = 441.22(3), c = 742.89(4) pm, wR = 0.0626, 1325 F 2 values, 45 variables for Ca1.692(8) Pt2Sn3.308(8) and CeNiSi2 type, Cmcm, a = 462.59(5), b = 1932.8(2), c = 458.00(5) pm, wR = 0.0549, 481 F 2 values, 18 variables for SrPtSn2. The calcium compound shows a homogeneity range Ca1+x Pt2Sn4−x with substantial Sn4/Ca2 mixing on one of the 4c Wyckoff positions. The [PtSn2] network is characterized by Pt–Sn (269–281 pm) and Sn–Sn (306–336 pm) bonding interactions. SrPtSn2 contains two different tin substructures: (i) Sn1–Sn1 zig-zag chains (282 pm) and (ii) orthorhombically distorted Sn2 squares (326 pm) with stronger and weaker Sn–Sn bonding. Together, the platinum and tin atoms build up a three-dimensional [PtSn2] network in which the platinum atoms have a distorted square-pyramidal tin coordination with Pt–Sn distances ranging from 261–270 pm. EuAuSn2 also crystallizes with the CeNiSi2-type structure with the lattice parameters a = 453.9(1), b = 2018.9(5) and c = 456.8(1) pm. Temperature dependent magnetic susceptibility studies indicate europium(II) with an experimental magnetic moment of 8.28(2) µB per Eu atom. EuAuSn2 is ordered antiferromagnetically at T N = 14.8(2) K. 151Eu Mössbauer spectra confirm the oxidation state +2 for europium (isomer shift δ = −11.17(2) mm s−1) and the magnetic ordering at low temperature (21.8 T magnetic hyperfine field at 6 K).

RhSn3 and the Modifications of RhSn4 – Structure and 119Sn Mössbauer spectroscopic characterization

Single crystals of the high-temperature modification of RhSn4 were obtained from a tin flux (1:20 molar ratio; final annealing at 920 K; dissolution of the tin matrix in 2N HCl). The structure was refined from single-crystal X-ray diffractometer data: I41/acd, a=629.73(5), c=2288.36(18) pm, wR2=0.0382, 447 F2 values and 14 variables. β-RhSn4 is isotypic with β-IrSn4. The rhodium atoms have slightly distorted square-antiprismatic tin coordination with Rh–Sn distances of 4×273.4 and 4×274.1 pm. The RhSn8 units are condensed via common edges to layers that are staggered with respect to each other and stacked in ABCD sequence. A 119Sn Mössbauer spectroscopic characterization of ß-RhSn4 and the stannides RhSn3 and α-RhSn4 shows the typical isomer shifts for transition metal stannides. Only for α-RhSn4 the three crystallographically independent tin sites could be resolved, a consequence of the different s-electron density. Treatment of α-RhSn4 under high-pressure (up to 10 GPa)/high-temperature (up to T=1370 K) conditions leads to decomposition into Rh1.5Sn, RhSn2 and β-Sn.

The Stannides EuPd2Sn2, EuPt2Sn2, EuAu2Sn2, and Eu5.4Sn5.6 – Structure and Magnetic Properties

The europium stannides EuT2Sn2 (T = Pd, Pt, Au) and Eu3Ag5.4Sn5.6 were synthesized by highfrequency melting of the elements in sealed niobium ampoules in a water-cooled sample chamber. All samples were characterized by powder X-ray diffraction. The EuT2Sn2 (T = Pd, Pt, Au) stannides crystallize with the CaBe2Ge2-type structure, space group P4/nmm. The structure of EuPd2Sn2 was refined from single-crystal X-ray diffractometer data: a = 462.44(8), c = 1045.8(3) pm, wR = 0.0402, 237 F2 values and 15 refined variables. The palladium and tin atoms build up a threedimensional [Pd2Sn2] polyanionic network, exclusively with Pd-Sn interactions (261 - 269 pm). The Pd1 and Pd2 atoms have square-pyramidal and tetrahedral tin coordination, respectively. The europium atoms fill large voids within the network. They are coordinated to eight palladium and eight tin atoms. Temperature-dependent magnetic susceptibility studies confirm a stable divalent ground state of the europium atoms. The compounds become ordered antiferromagnetically below 6.3 (EuPd2Sn2), 6.1 (EuPt2Sn2) and 7.7 K (EuAu2Sn2). Eu3Ag5.4Sn5.6 adopts a partially ordered variant of the La3Al11 type, space group Immm, a = 471.33(8), b = 1382.5(4), c = 1032.4(2) pm, wR = 0.0449, 692 F2 values, 30 variables. The three-dimensional [Ag5.4Sn5.6] network shows one silver and one tin site besides two sites with substantial Ag/Sn mixing. The two crystallographically independent europium atoms fill larger and smaller cavities within the [Ag5.4Sn5.6] network. Eu3Ag5.4Sn5.6 also shows divalent europium and antiferromagnetic ordering at TN = 6:9 K. A 151Eu Mössbauer spectrum of Eu3Ag5.4Sn5.6 at 5.2 K shows an isomer shift of δ = −10.61 mms−1, typical for Eu(II) compounds, and a magnetic hyperfine field splitting of BHf = 5.9 T. 119Sn Mössbauer spectra of the four stannides show isomer shifts in the range of δ = 1.78 - 2.20 mms−1, usually observed for tin in intermetallic compounds.

Reaction products of diorganotin(IV) oxides, R2SnO, with nitric acid. Part 1: R = methyl, ethyl, and isopropyl

The reaction of diorganotin(IV) oxides, R2SnO with R = Me, Et, and i-Pr, with nitric acid in different stoichiometric ratios resulted in the formation of different products depending on the organic groups. The diorganotin(IV) nitrate hydroxides Me2Sn(NO3)(OH) (1a) Et2Sn(NO3)(OH), α-1b, β-1b, i-Pr2Sn(NO3)(OH) (1c), the diisopropyltin(IV) dinitrate dihydrate, i-Pr2Sn(NO3)2·2H2O (2c) and the diisopropyltin(IV) nitrate oxalate dihydrate, [i-Pr2Sn(NO3)]2Ox·2H2O (3) as side-product. On examination of the solubility of the primary reaction products in different solvents, the two additional compounds Me2Sn(NO3)(OH)·DMSO (4) and 2i-Pr2Sn(NO3)2·3DMSO = [i-Pr2Sn(NO3)(dmso)3] [i-Pr2Sn(NO3)3] (5) have been isolated. All compounds have been structurally characterized by single crystal X-ray diffraction with special respect to dimensionality (1a, α-1b, 1c = dimeric molecules hydrogen bonded to one-dimensional chains; β-1b = two-dimensional coordination polymer; 2c = monomeric; 3 = monomeric, tin atoms linked via a double side-on chelating oxalate ion; 4 = dimeric, 5 = monomeric anion/cation), tin coordination (trigonal-bipyramidal = 1a, α-1b, 1c; six-fold = β-1b; seven-fold = 3, 4, 5-cation; eight-fold = 2c, 5-anion) and nitrate bonding modes (monodentate = 1a, α-1b, 1c; unsymmetrical bidentate = 3, symmetrical bidentate = 3, 4, 5-cation, 5-anion; syn-anti bridging = β-1b), the latter one being analysed using both, Sn–O and N–O distances.

SrCo2Sn8 and BaCo2Sn8: Tin-rich Stannides with Distorted SnSn6 Octahedra within Three-dimensional [Co2Sn8] Networks

The tin-rich stannides SrCo2Sn8 and BaCo2Sn8 were synthesized from the elements in sealed tantalum tubes. They crystallize with a new structure type, space group Cccm with a=1006.0(3), b=1514.4(6), c=1385.0(6) pm for SrCo2Sn8 and a=1032.8(2), b=1516.8(3), c=1405.1(3) pm for BaCo2Sn8. The structure of the barium compound was refined on the basis of single-crystal Xray diffractometer data: wR2=0.0450, 1715 F2 values, 57 variables. The cobalt atoms have seven nearest tin neighbors with Co-Sn distances ranging from 257 to 273 pm. These CoSn7 units are condensed via common rectangular faces to [Co2Sn10] double units which build up a covalently bonded three-dimensional network through Sn-Co-Sn bridges. Larger voids left by this network are filled by the barium and the Sn2 atoms. The latter have distorted octahedral tin coordination with Sn2- Sn distances of 311 - 315 pm. The barium atoms have 13 nearest tin neighbors (352 - 399 pm Ba-Sn). Temperature-dependent magnetic susceptibility data of BaCo2Sn8 show Pauli paramagnetism.