Search Results

You are looking at 1 - 10 of 20 items

  • Author: Wolfgang Schnick x
Clear All Modify Search

Phosphorothionic triamide SP(NH2)3 is obtained by slow addition of SPCl3 dissolved in dry CH2Cl2 to a satured solution of NH3 in CH2Cl2 at —50°C. Ammonium chloride is removed from the resulting precipitate by treatment with HNEt2 followed by extraction with CH2Cl2. Coarse crystalline SP(NH2)3 is obtained after recrystallization from dry methanol. The crystal structure of SP(NH2)3 has been determined by single crystal X-ray methods (Pbca; a = 922.3(1), b = 953.8(1), c = 1058.4(2) pm, Z = 8). In the crystals the molecules show non-crystallographic point symmetry C8. The P—S bond (195.4(1) pm) is slightly longer than in SPCl3. From P—N bond lengths of about 166 pm a significant electrostatic strengthening of the P—N single bonds is assumed. Weak intermolecular hydrogen bonding interactions (N —H · · · N ≥ 329.5 pm; N — H · · · S ≥ 348.3 pm) are observed.

Investigation of thermal properties shows a melting temperature of 115°C for SP(NH2)3. According to combined DTA/TG and MS investigations above this temperature the compound decomposes by evolution of H2S and NH3 to yield amorphous phosphorus(V)nitride.

[(NH2)3PNP(NH2)3]Cl has been prepared by a three step synthesis. The last step is the ammonolysis of [Cl3PNPCl3]Cl. Single crystals of 1,1,1,3,3,3-hexaamino-1λ5, 3λ5-diphosphazenium chloride were obtained from an acetonitrile solution in a temperature gradient between 60 °C and room temperature. Between room temperature and -100 °C [(NH2)3PNP(NH2)3]Cl is subject to a phase transition. Therefore, the crystal structure was determined by single crystal X-ray methods at room temperature (P1̄, a = 584.7(1) pm, b = 732.1(1) pm, c = 1092.0(2) pm. q = 71.05(3)°, β = 76.36(3)°, γ = 89.83(3)°, Z = 2, R = 4.75 %, wR = 2.47 %). The cation [(NH2)3PNP(NH2)3]+ is built up by two corner sharing PN4 tetrahedra. Remarkably short P-N bonding distances have been observed and both PN4 tetrahedra exhibit a significant distortion resulting in two large and four small N-P-N bond angles.

Abstract

Ba2Na(CN2)(CN)3 was obtained by the reaction of Ba2N with melamine and NaCN at 700 °C. The compound was structurally characterized by single-crystal X-ray investigations (Fd3̄m, a = 1518.8(3) pm, Z = 16). In the crystal structure the Ba2+ ions form a cubic close packed arrangement, the Na+ and the CN2- 2 ions occupy the octahedral interstices. The CN-ions are located within the close packed Ba2+ layers. The unit cell of Ba2Na(CN2)(CN)3 contains two interpenetrating substructures of the zinc-blende structure type, building up a variant of NaTl. A reversible phase transition has been observed during cooling of the compound. Whereas the Ba2(CN2)(CN)3 sublattice remains nearly unaffected in this process, the Na+ ions of the low-temperature phase are statistically distributed on two crystallographic positions.

Abstract

[P(NH2)4]Cl has been prepared by ammonolysis of phosphorus pentachloride in liquid ammonia. The product was purified by reacting the byproduct, ammonium chloride, with diethylamine and removing the diethylamine hydrochloride. Suitable single crystals were obtained from an acetonitrile solution in a temperature gradient between 60 °C and room temperature. The crystal structure of [P(NH2)4]Cl has been determined by single crystal X-ray methods (Pbcn, a = 470.8(2), b = 1622.3(3), c = 756.3(2) pm, Z = 4). In the solid, [P(NH2)4]+ and Cl- ions are found, resembling a TlI-analogous structure.

The N-H···Cl distances indicate N-H···Cl hydrogen bonding interactions. The distortion of the P-N sceleton of the cation and the very short P-NH2 distances (mean value: 161.2 pm) have been confirmed by ab initio calculations, which show a generalized anomeric effect of the electron pairs at nitrogen and pπdπ bonding.

Abstract

The title compound has been prepared starting from phosphorothionic triamide SP(NH2)3 by methylation of the sulfur atom and subsequent ammonolysis reaction in dry acetonitrile and dichloromethane, respectively, both at room temperature. Suitable single crystals are obtained from an acetonitrile solution in a temperature gradient between 70 °C and room temperature. The crystal structure of [P(NH2)4]I has been determined by single crystal X-ray methods (P4/nbm; a = 842.6(2), c = 486.7(2) pm, Z = 2). In the solid [P(NH2)4]+ - and I-ions are found with significant N - H···I-hydrogen bonding interactions between anions and cations (H -I: 276.4 pm). The P - N - bond length in the cation (160.7(2) pm) represents the shortest P - NH2 bond distance reported to date indicating a significant electrostatic strengthening. The condensation behaviour of [P(NH2)4]I in solution and in the solid has been investigated.

Abstract

(NH2)2P(S)N=P(NH2)3 has been prepared by a two step synthesis. Suitable single crystals were obtained from an acetonitrile solution in a temperature gradient between 60 °C and room temperature. The crystal structure of (NH2)2P(S)N=P(NH2)3 has been determined by single crystal X-ray methods (P21/c, a = 998.27(9) b = 762.78(8), c = 1007.70(15) pm, β = 107.340(7)°, Z = 4). In the crystal structure each hydrogen atom is subject to a hydrogen bond. Four N-H -N hydrogen bonding interactions per molecule build up a framework connecting two molecules in eight-membered rings. Each sulfur atom shows six distances N-H···S in the range of weak hydrogen bonding interactions.

The ion exchange reaction between ammonium cyanoureate NH4[H2NC(=O)NCN] and zinc chloride yielded single crystals of the urea derivative cyanoguanylurea H2NC(=O)NHC(NH2)NCN, which was obtained as a by-product alongside zinc cyanoureate and traces of ammonium chloride. It is assumed that owing to its Lewis and Brønsted acidity, the hydrated Zn2+ ion acts as a catalyst, promoting the degradation of the cyanoureate anion with subsequent formation of the title compound. The crystal structure was solved in the centrosymmetric space group P21/n (a = 476.7(1), b = 965.3(2), c = 1165.6(2) pm, β = 97.75(3)°, V = 531.4(2) 106 pm3, Z = 4, T = 200 K). In the solid there are non-planar cyanoguanylurea molecules with a dicyandiamide-type C-N system, building up a layered structure with sparse interlayer contacts and significant hydrogen bonding within the layers

By the reaction of (Me3SiNH)2SiClNMe2 with TiCl4 the by-product [Me2NH2]2[TiCl6] was obtained in form of crystals suitable for single-crystal XRD (Pnnm, Z = 2, a = 722.01(3), b = 1428.36(5), c = 703.31(3) pm, T = 200 K, 901 independent reflections, 57 variables, R1 = 0.0636). The product was also synthesized in higher yield by the stoichiometric reaction of two equivalents of [Me2NH2]Cl with TiCl4 in CHCl3 at room temperature as a yellow crystalline powder. Bis(dimethylammonium) hexachlorotitanate is built up from [TiCl6]2- anions forming elongated octahedra and [Me2NH2]+ ions. The [TiCl6]2- ions are connected by the [Me2NH2]+ ions through N-H···Cl hydrogen bridges forming an arrangement which resembles that of an expanded rutile structure type. The elongation of the [TiCl6]2- octahedra was also verified by IR and Raman spectroscopy, confirming a local symmetry reduction from Oh to D4h. The solubility of [Me2NH2]2[TiCl6] in MeNO2 and MeCN was determined by means of 14N-NMR to be about 0.1 mol% and 0.3 mol%, respectively.

CaMg2N2 (trigonal, P3̄ m 1 (Nr. 164); a = 354.046(1), c = 609.079(2) pm; Z = 1) is isotypic to the anti-La2O3 structure with octahedral and tetrahedral coordination for Ca2+ and Mg2+ ions, respectively. The compound has been prepared by the reaction o f the binary nitrides Ca3N2 and Mg3N2 (molar ratio 1:2) in a tungsten crucible under a pure nitrogen atmosphere at 1050 °C. The formation of the solid CaMg2N2 may be interpreted in analogy to reactions o f related oxides as an acid-base reaction between the binary nitrides with different coordination tendencies of Ca2+ and Mg2+ ions. An analysis of the binary aristotype anti-La2O3 indicates that this structure is predisposed for building ternary phases.

Abstract

The chlorinated titanium amides [(Cl3Si)2N]2TiCl2 (1) and (Cl3Si)2NTiCl3 have been syn­thesized selectively from hexachlorodisilazane lithium and TiCl4. The crystal structure of 1 was determined by single crystal X-ray methods at room temperature (P212121, a = 1232.4(2), b = 1265.5(2), c -1469.1(2) pm, Z = 4). The central titanium atom of 1 is bound to two nitrogen atoms and two Cl atoms and is weakly coordinated further by two Cl atoms of the trichlorosilyl groups.