Photoluminescence of Mn2+ in the Borosulfate Zn[B2 (SO4 )4 ] : Mn2+ -A Tool to Detect Weak Coordination Behavior of Ligands.

The impact of the surrounding ligand field is successfully exploited in the case of Eu2+ to tune the emission characteristics of inorganic photoactive materials with potential application in, e.g., phosphor-converted white light-emitting diodes (pc-wLEDs). However, the photoluminescence of Mn2+ related to intraconfigurational 3d5 -3d5 transitions is also strongly dependent on local ligand field effects and has been underestimated in this regard so far. In this work, we want to revive the idea how to electronically tune the emission color of a transition metal ion in inorganic hosts by unusual electronic effects in the metal-ligand bond. The concept is explicitly demonstrated for the weakly coordinating layer-like borosulfate ligand in the Mn2+ -containing solid solutions Zn1-x Mnx [B2 (SO4 )4 ] (x = 0, 0.03, 0.04, 0.05, 0.10). Zn[B2 (SO4 )4 ]:Mn2+ shows orange narrow-band luminescence at 590 nm, which is an unusually short wavelength for octahedrally coordinated Mn2+ and indicates an uncommonly weak ligand field. On the other hand, the analysis of the interelectronic Racah repulsion parameters reveals ionic Mn-O bonds with values close to the Racah parameters of the free Mn2+ ion. Overall, this strategy demonstrates that electronic control of the metal-ligand bond can be a tool to make Mn2+ a potent alternative emitter to Eu2+ for inorganic phosphors.

Cd[B2(SO4)4] and H2[B2(SO4)4] - a phyllosilicate-analogous borosulfate and its homeotypic heteropolyacid.

Borosulfates consist of heteropolyanionic networks of corner-shared (SO4)- and (BO4)-tetrahedra charge compensated by metal or non-metal cations. The anionic substructures differ significantly, depending on the different branching of the silicate-analogous borosulfate building blocks. However, only one acid has been characterized by single crystal X-ray diffraction so far. Herein, we present H2[B2(SO4)4] as the first phyllosilicate analogue representative, together with the homeotypic representative Cd[B2(SO4)4]. The latter can be considered the cadmium salt of the former. Their crystal structures and crystallographic relationship are elucidated. For H2[B2(SO4)4], the bonding situation is examined using Hirshfeld-surface analysis. Further, the optical and thermal properties of Cd[B2(SO4)4] are investigated by FTIR and UV-Vis spectroscopy, thermogravimetry, as well as temperature-programmed powder X-ray diffraction.

Stabilizing the Homopolycation (I4 )2+ with a Hexasulfate in (I4 )[S6 O19 ] and a Borosulfate in (I4 )[B(S2 O7 )2 ]2.

The reaction of elemental iodine and SO3 in a sealed glass ampoule yielded a turquoise-colored solution. At temperatures below 7 °C, deep red crystals of (I4 )[S6 O19 ] grow. With the addition of B2 O3 and pyridine-SO3 complex red crystals of (I4 )[B(S2 O7 )2 ]2 can be obtained after heating the mixture to 120 °C. The combination of an (I4 )2+ cation with oxoanions has previously not been observed. Both anions have a significant but different influence on the structural properties of the (I4 )2+ cation.

Polycations Stabilised by Borosulfates: [Au3 Cl4 ][B(S2 O7 )2 ] and the One-Dimensional Metal [Au2 Cl4 ][B(S2 O7 )2 ](SO3 ).

(SO4 )-rich silicate analogue borosulfates are able to stabilise cationic cluster-like and chain-like aggregates. Single crystals of [Au3 Cl4 ][B(S2 O7 )2 ] and [Au2 Cl4 ][B(S2 O7 )2 ](SO3 ) were obtained by solvothermal reaction with SO3 , and the electronic properties were investigated by means of density functional theory-based calculations. [Au3 Cl4 ][B(S2 O7 )2 ] exhibits a cluster-like cation, and the cationic gold-chloride strands in [Au2 Cl4 ][B(S2 O7 )2 ](SO3 ) are found to resemble one-dimensional metallic wires. This is confirmed by polarisation microscopy.

Triple-Vertex Linkage of (BO4 )-Tetrahedra in a Borosulfate: Synthesis, Crystal Structure, and Quantum-Chemical Investigation of Sr[B3 O(SO4 )4 (SO4 H)].

Borosulfates are classified as silicate analogue materials. The number of crystallographically characterized compounds is still limited, whereas the structural diversity is already impressive. The anionic substructures of borosulfates exhibit vertex-connected (BO4 )- and (SO4 )-tetrahedra, whereas bridging between two (SO4 )- or even between two (BO4 )-tetrahedra is scarce. The herein presented compound Sr[B3 O(SO4 )4 (SO4 H)] is the first borosulfate with a triple-vertex linkage of three (BO4 ) tetrahedra via one common oxygen atom. DFT calculations complement the experimental studies. Bader charges (calculated for all atoms) as well as charge-density calculations give hint to the electron distribution within the anionic substructure and density-of-states calculations support the interpretation of the bonding situation.

Ni[B2 (SO4 )4 ] and Co[B2 (SO4 )4 ]: Unveiling Systematic Trends in Phyllosilicate Analogue Borosulfates.

Borosulfates are compounds analogous to silicates, with heteropolyanionic subunits of vertex-linked (SO4 )- and (BO4 )-tetrahedra. In contrast to the immense structural diversity of silicates, the number of borosulfates is yet very limited and the extent of their properties is still unknown. This is particularly true for representatives with phyllosilicate and tectosilicate analogue anionic substructures. Herein, we present Ni[B2 (SO4 )4 ] and Co[B2 (SO4 )4 ], two new borosulfates with phyllosilicate analogue topology. While the anionic subunits of both structures are homeotypic, the positions of the charge compensating cations differ significantly: NiII is located between the borosulfate layers, while CoII -in contrast-is embedded within the layer. Detailed analysis of these two structures based on single-crystal X-ray diffraction, magnetochemical investigations, X-ray photoelectron spectroscopy, and quantum chemical calculations, unveiled the reasons for this finding. By in silico comparison with other divalent borosulfates, we uncovered systematic trends for phyllosilicate analogues leading to the prediction of new species.

Borosulfates-Synthesis and Structural Chemistry of Silicate Analogue Compounds.

Borosulfates are oxoanionic compounds consisting of condensed sulfur- and boron-centered tetrahedra. Hitherto, they were mostly achieved from solvothermal syntheses in SO3 -enriched sulfuric acid, or from reactions with the superacid H[B(HSO4 )4 ]. The crystal structures are very similar to those of the corresponding class of silicates and their substitution variants, especially regarding the typical structural motif of corner-sharing tetrahedra. However, the borosulfates are supposed to be even more versatile, because (BO3 ) units might also be part of the anionic network. The following article deals with detailed reports on the different synthesis strategies, the crystal chemistry of borosulfates in comparison to silicates, and their hitherto identified properties.

RE2[B2(SO4)6] (RE = Y, La-Nd, Sm, Eu, Tb-Lu): a silicate-analogous host structure with weak coordination behaviour.

The rare earth borosulfates RE2[B2(SO4)6] with RE = Y, La-Nd, Sm, Eu and Tb-Lu were synthesised under solvothermal conditions starting from the metal chlorides (Pr, Nd, Eu), the metal oxides (Y, La, Ce, Sm, Tb, Dy, Er, Tm, Lu), or the metal powders (Ho, Yb). They crystallize isotypically with Gd2[B2(SO4)6] in space group C2/c (Z = 4, a = 1346.9(3)-1379.24(17) pm, b = 1136.4(3)-1158.87(14) pm, c = 1079.9(3)-1139.54(14) pm, ß = 93.369(8)-93.611(4)°). The anionic structure consists of an open-branched vierer single ring {oB, 1r}[B2S2O12(SO3)4]6-, similar to the mineral eakerite (Ca2Al2Sn[Si6O18](OH)2·2H2O) which contains {oB, 1r}[Si4O12(SiO3)2]12- moieties. The fluorescence spectroscopy of the samples with RE = Ce, Eu and Tb features emissions in the deep UV, the red, and the green part of the spectrum and furthermore revealed a weak coordination behaviour of the borosulfate anion. Thermal analysis of Eu2[B2(SO4)6] showed the highest thermal stability observed for borosulfates so far; respective trends within the borosulfate family are discussed. Additionally, the compounds were characterised by magnetic measurements, vibrational and 151Eu Mößbauer spectroscopy.

UF4 and the High-Pressure Polymorph HP-UF4.

A laboratory-scale synthesis of UF4 is presented that utilizes the reduction of UF6 with sulfur in anhydrous hydrogen fluoride. An excess of sulfur can be removed by vacuum sublimation, yielding pure UF4 , as shown by powder X-ray diffraction, micro X-ray fluorescence analysis, infrared and Raman spectroscopy, as well as magnetic measurements. Furthermore, a single-crystalline, high-pressure modification of UF4 was obtained in a multi-anvil press at elevated temperatures. The high-pressure polymorph HP-UF4 was characterized by means of single-crystal and powder X-ray diffraction, as well as by magnetic measurements, and presents a novel crystal structure type. Quantum-chemical calculations show the HP-modification to be 10 kJ mol-1 per formula unit higher in energy compared to UF4 .

Cu[B2 (SO4 )4 ] and Cu[B(SO4 )2 (HSO4 )]-Two Silicate Analogue Borosulfates Differing in their Dimensionality: A Comparative Study of Stability and Acidity.

Borosulfates are an ever-expanding class of compounds and the extent of their properties is still elusive. Herein, the first two copper borosulfates Cu[B2 (SO4 )4 ] and Cu[B(SO4 )2 (HSO4 )] are presented, which are structurally related but show different dimensionalities in their substructure: While Cu[B2 (SO4 )4 ] reveals an anionic chain, ∞1 [B(SO4 )4/2 ]- , with both a twisted and a unique chair conformation of the B(SO4 )2 B subunits, Cu[B(SO4 )2 (HSO4 )] reveals isolated [B2 (SO4 )4 (HSO4 )2 ]4- anions showing exclusively a twisted conformation. The complex anion can figuratively be obtained as a cut-out from the anionic chain by protons. Comparative DFT calculations based on magnetochemical measurements complement the experimental studies. Calculation of the pKa  values of the two conformers of the [B2 (SO4 )4 (HSO4 )2 ]4- anion revealed them to be more similar to silicic than to sulfuric acid, highlighting the close relationship to silicates.

CaB2 S4 O16 : A Borosulfate Exhibiting a New Structure Type with Phyllosilicate Analogue Topology.

The reaction of Ca(CO3 ) with H3 BO3 in oleum (20 % SO3 ) yielded colorless single-crystals of CaB2 S4 O16 (monoclinic, P21 /c, a=5.5188(2), b=15.1288(6), c=13.2660(6) Å, ß=92.88(1)°, V=1106.22(8) Å3 ). X-ray single-crystal structure analysis revealed a phyllosilicate-analogue anionic sub-structure, forming 2D infinite anionic layers, which exhibit an unprecedented arrangement of condensed twelve-membered (zwölfer) and four-membered (vierer) rings of corner-shared (SO4 ) and (BO4 ) tetrahedra. Charge compensation is achieved by Ca2+ cations, residing exclusively above the centers of the twelve-membered rings. DFT investigations on the solid-state structure corroborate the experimental findings and allow for a detailed valuation of charge distribution within the anionic network and an assignment of vibrational frequencies.

Palladium(IV) in an Oxoanionic Environment: The XeF2 Assisted Synthesis of [Pd(S2 O7 )3 ](2.).

For the first time tetravalent palladium is detected, coordinated exclusively by simple oxoanions. Stabilization was achieved by formation of the [Pd(S2 O7 )3 ](2-) complex in which three chelating disulfate groups surround the metal atom. The salt K2 [Pd(S2 O7 )3 ] could only be obtained if the reaction of K2 [PdCl6 ] and neat SO3 was performed in the presence of XeF2 .

A Highly Triflated Rare-Earth Ion in [Eu(O3SCF3)8](5-).

The reaction of Eu2O3 with fuming nitric acid, trifluormethanesulfonic acid, and its anhydride in torch-sealed glass ampoules at 120 °C gave the europium compound (NO)5[Eu(O3SCF3)8] (orthorhombic, Fddd, Z = 16, a = 1932.69(4), b = 2878.44(7), c = 2955.12(7) pm, V = 16439.7(7) Å(3)). The compound exhibits the [Eu(O3SCF3)8](5-) anion showing for the first time a lanthanide ion that is exclusively coordinated by eight triflate anions. The anion has been further investigated by DFT calculations, which also allowed clear assignment of the vibrational spectra. Moreover, magnetochemical and luminescence measurements gave additional insight into the properties of this complex. The luminescence spectra revealed that the Eu(3+) ions are in a pseudo D4d symmetric environment.

Chelating and Linking S4O13(2-) Anions: Synthesis and Characterization of the Bis-(tetrasulfato) Palladates M2[Pd(S4O13)2] (M = NH4, Rb, NO) and the Sodium Palladium Tetrasulfate Na2Pd(S4O13)2.

The reaction of SO3 with either the palladium chlorides M2PdCl6 (M = Rb, NH4) or the nitrato-palladate (NO)2[Pd(NO3)4] at elevated temperature led to yellow single crystals of the complex palladates M2[Pd(S4O13)2] (M = NH4: triclinic, P1̅, a = 7.3882(3) Å, b = 8.5223(3) Å, c = 9.2712(4) Å, α = 71.945(2)°, ß = 88.910(2)°, γ = 72.603(2)°, V = 527.88(4) Å3; M = NO: triclinic, P1̅, a = 7.2881(3) Å, b = 8.9125(2) Å, c = 8.9220(4) Å, α = 75.546(2)°, ß = 89.151(2)°, γ = 69.516(2)°, V = 524.02(4) Å3; M = Rb: triclinic, P1̅, a = 7.4468(4) Å, b = 8.5066(4) Å, c = 9.2477(4) Å, α = 72.321(2)°, ß = 88.512(2)°, γ = 72.128(2)°, V = 529.75(4) Å3). In the isotypic compounds, the Pd atom is in square planar oxygen coordination, achieved by two bidentate-chelating tetrasulfate anions. The reaction of Na2PdCl6 with neat SO3 afforded yellow crystals of Na2Pd(S4O13)2 (monoclinic, P21/c, a = 6.9953(4) Å, b = 15.9420(9) Å, c = 9.2299(5) Å, ß = 100.235(2)°, V = 1012.45(1) Å3). The structure exhibits no palladate complexes but an anionic two-dimensional network, according to ∞2[Pd(S4O13)(4/2)]2­. The latter shows the tetrasulfate anions acting as bidentate-bridging ligands. The tetrasulfato-palladates were studied in more detail by means of thermal analyses and infrared (IR) spectroscopy. The observed IR bands were assigned according to quantum chemical calculations performed on the anion [Pd(S4O13)2]2­.

Oxoanionic noble metal compounds from fuming nitric acid: the palladium examples Pd(NO3)2 and Pd(CH3SO3)2.

The oxidation of elemental palladium at 100 °C in a mixture of fuming nitric acid and a pyridine-SO3 complex leads to the anhydrous nitrate Pd(NO3)2 (monoclinic, P2(1)/n, Z=2, a=469.12(3) pm, b=593.89(3) pm, c=805.72(4) pm, ß=105.989(3)°, V=215.79(2) Å(3)). The Pd(2+) ions are in square-planar coordination with four monodentate nitrate groups which are connected to further palladium atoms, leading to a layer structure. The reaction of elemental palladium with a mixture of fuming nitric acid and methanesulfonic acid at 120 °C leads to single crystals of Pd(CH3SO3)2 (monoclinic, P2(1)/n, Z=2, a=480.44(1) pm, b=1085.53(3) pm, c=739.78(2) pm, ß=102.785(1)°, V=376.254(17) Å(3)). Also in this structure the Pd(2+) ions are in square-planar coordination with four monodentate anions; however, the connection to adjacent palladium atoms leads to a chain-type structure. The thermal decomposition of the compounds has been investigated by means of DSC/TG measurements. Furthermore, IR and Raman spectra have been recorded, and an assignment of the observed vibrational frequencies has been carried out based on theoretical investigations.

Oxidizing elemental platinum with oleum under harsh conditions: the unique tris(disulfato)platinate(IV) [Pt(S2O7)3]2- anion.

For the first time, direct oxidation of elemental platinum by a mineral acid to its tetravalent state was observed in course of the reaction of platinum with oleum (65 % SO3) in the presence of barium carbonate. The reaction has been carried out in torch-sealed glass ampoules at 160 °C and gave yellow single crystals of Ba[Pt(S2O7)3](H2SO4)0.5(H2S O7)0.5 (triclinic, P1, Z=2, a=992.05(2), b=1069.07(3), c=1114.22(3) pm, α=69.49(7), ß=72.96(2), γ=72.93(1)°, V=1033.95(5) Å(3)). The structure of Ba[Pt(S2O7)3](H2SO4)0.5(H2S2O7)0.5 exhibits the unique tris-(disulfato)-platinate anion [Pt(S2O7)3](2-) with three chelating disulfate groups coordinated to the platinum atom. Charge balance is achieved by the Ba(2+) ions, which are coordinated by (S2O7)(2-) groups from the platinate complex and by disordered sulfuric acids and disulfuric acid molecules. Thermal decomposition of the bulk material revealed elemental platinum and barium sulfate as decomposition residual.

Ba2[Pd(HS2O7)2(S3O10)2]: a heteroleptic polysulfatopalladate.

The oxidation of elemental palladium with oleum (65 % SO3) in the presence of barium carbonate in torch-sealed glass ampoules at 180 °C leads to yellow single crystals of the heteroleptic palladate Ba2[Pd(HS2O7)2(S3O10)2] (triclinic, P1; Z=1; a=884.18(3), b=927.68(3), c=938.77(4) pm; α=60.473(1), ß=80.266(2), γ=87.746(2)°). The crystal structure shows the Pd(2+) ions in a square-planar coordination of oxygen atoms of two hydrogendisulfate as well as of two trisulfate anions. The compound is the first example of the rarely seen S3O10(2-) and HS2O7(-) anions acting as ligands in a complex anion and, moreover, the first heteroleptic polysulfatometallate known so far. The complex formation leads to a stabilization of the trisulfate anion relative to its uncoordinated congener. Ba2[Pd(HS2O7)2(S3O10)2] has been further characterized by vibrational spectroscopy and quantum chemical calculations. Thermal analyses by means of thermogravimetric/differential thermal analysis (TG/DTA) measurements show that the compound decomposes to yield elemental palladium and BaSO4.

Ferromagnetic ordering in the layer-structured Pd(HS(2)O(7))(2).

The reaction of (NO2 )(CF3 SO3 ) and elemental palladium in oleum (65 % SO3 ) leads to violet single crystals of Pd(HS2 O7 )2 (monoclinic, P21 /c, Z=2, a=927.80(9), b=682.58(7), c=920.84(9) pm, ß=117.756(2)°, wR2 =0.0439). In the crystal structure, the Pd(2+) ions show an uncommon octahedral coordination of six oxygen atoms belonging to six HS2 O7 (-) ions. The linkage of [PdO6 ] octahedra and the hydrogendisulfate anions leads to a layer structure, and the layers are held together by hydrogen bonds. The unusual coordination of the Pd(2+) ions results in an electronic d(8) high-spin configuration, which leads to the paramagnetic behavior of the compound. Moreover, at low temperature, a ferromagnetic ordering was observed with a Curie temperature of 8 K.

Bis(tetrasulfato)palladate, [Pd(S(4)O(13))(2)](2-).

SOS: The first coordination compound containing polysulfate ligands was obtained under harsh conditions from the reaction of K(2)[PdCl(4)] and SO(3). The compound contains a Pd(2+) ion coordinated by two chelating tetrasulfate anions (see structure, Pd red, S yellow, O blue), which leads to a significant stabilization of the polysulfate anions compared to their uncoordinated analogues.