Synthesis,Crystal Structure,and High Temperature Behavior of Zr3N4

A red-brown zirconium nitride was prepared by ammonolysis of ZrCl₄. Chemical analysis leads to a composition of Zr₃N₄. It is not possible to distinguish between the space groups Pnam and Pna2₁ in the case of Zr₃N₄ using powder methods. The lattice constants are: a = 972.94(5) pm, b = 1081.75(6) pm, c = 328.10(1) pm (Z = 4). X-ray powder diffraction data were used for structure refinement. The high temperature behavior was investigated with in situ XRD methods. Zr₃N₄ decomposes into ZrN and nitrogen gas at temperatures above 800°C.     

From cyclotetrasilazane [(CH3)2SiNH]4 via crystalline silicon nitride imide Si2N2NH to α-Si3N4

α-Si₃N₄ is synthesized by an ammonia thermal synthesis using a cyclic oligosilazane, [(CH₃)₂SiNH]₄, as the starting material. [(CH₃)₂SiNH]₄ reacts in the presence of ammonia at 900°C and 80 MPa pressure to give silicon nitride imide (Si₂N₂NH). Subsequently, Si₂N₂NH is converted into α-Si₃N₄ by thermal decomposition at 1500°C and 0.1 MPa nitrogen with the simultaneous loss of NH₃.     

Azidokomplexe von Vanadium(IV) und Vanadium(V): (Ph4P)2[VOCl2(μ‐N3)]2 und (Ph4P)2[VOCl(μ‐N3)(N3)2]2

Azido Complexes of Vanadium(IV) and Vanadium(V): (Ph₄P)₂[VOCl₂(μ‐N₃)]₂ and (Ph₄P)₂[VOCl(μ‐N₃)(N₃)₂]₂ (Ph₄P)₂[VOCl₂(μ‐N₃)]₂ ( 1 ) was prepared by reaction of (Ph₄P)[VO₂Cl₂] with trimethylsilylazide in the molar ratio 1:2 in dichloromethane solution to give dark green, moisture sensitive, non‐explosive single crystals. The reaction is accompanied by the formation of the dark blue side‐product (Ph₄P)₂[VOCl(μ‐N₃)(N₃)₂]₂ ( 2a ), which can be obtained as the main product by application of a large excess of Me₃SiN₃. Dark blue needles of 2a crystallize spontaneously from the CH₂Cl₂ solution within one hour at 4 °C. After standing at 4 °C under its mother liquid within 24 hours a first‐order phase transition of 2a occurs forming dark blue prismatic single crystals of 2b . According to single crystal X‐ray structure determinations, 2a and 2b crystallize in the same type of space group , however, with different lattice dimensions. The vanadium(IV) complex 1 is characterized by X‐ray structure determination and by vibrational spectroscopy (IR, Raman) as well as by EPR spectroscopy, whereas 2b is characterized by IR spectroscopy. 1 : Space group P2₁/n, Z = 2, a = 1009.5(1), b = 1226.6(2), c = 1943.0(2) pm, β = 98.42(1)°, R₁ = 0.0672. The complex anion forms centrosymmetric units with V₂N₂‐four‐membered rings with a V···V distance of 335.6(1) pm and coordination number five on the vanadium(IV) atoms. 2a : Space group , Z = 1, a = 1089.0(2), b = 1097.1(2), c = 1310.1(2) pm, α = 92.99(1)°, β = 106.12(2)°, γ = 117.05(2)°, V = 1309.8(4) ų, d_calc. = 1.440 g·cm^?3, R₁ = 0.0384. The complex anion forms centrosymmetric units of symmetry C_i with V₂N₂ four‐membered rings and VN bond lengths of 200.4(3) and 234.4(2) pm, respectively. The non‐bonding V···V distance amounts to 356.2(1) pm. 2b : Space group , Z = 1, a = 1037.3(2), b = 1157.6(2), c = 1177.2(2) pm, α = 98.48(2)°, ° = 103.82(2)°, γ = 106.33(2)°, V = 1281.8(4) ų, d_calc. = 1.471 g·cm^?3, R₁ = 0.0724. The structure of the complex anion is similar to the anion of 2a with VN bond lengths of the four‐membered V₂N₂ ring of 203.3(4) and 235.2(4) pm, respectively, and a non‐bonding V···V distance of 357.5(1) pm.     

On the Anion Distribution in Zr7O8N4

The effect of anion distribution on the stability of β‐zirconium oxide nitride Zr₇O₈N₄ (trigonal, ; a = 953.80(2) pm, c = 884.98(3) pm, Z=3) has been investigated quantum‐chemically. In agreement with experimental results for the structurally related β′‐type zirconium oxide nitride (Zr₇O₁₁N₂) nitride anions occupy sites in the central polyhedron of a Bevan cluster (A₇X₁₂ unit) in the most stable configurations. Other relevant structural ordering parameters are minimization of N^3?···N^3? contacts and of the number of quasi‐linear N–Zr–N bonds. The calculated electronic structure of β‐Zr₇O₈N₄ is in qualitative agreement with experimental observations.     

Molybdän‐ und Wolfram‐Komplexe mit MNS‐Sequenzen. Die Kristallstrukturen von [MoCl3(N3S2)(1,4‐Dioxan)2] und [Mo2Cl2(μ‐NSN)2(μ‐O)(NCMe3)(OCMe3)2]2

Molybdenum and Tungsten Complexes with MNS Sequences. Crystal Structures of [MoCl₃(N₃S₂)(1,4‐dioxane)₂] and [Mo₂Cl₂(μ‐NSN)₂(μ‐O)(NCMe₃)(OCMe₃)₂]₂ The cyclo‐thiazeno complexes [Cl₃MNSNSN]₂ of molybdenum and tungsten react with 1,4‐dioxane in dichloromethane suspension to give the binuclear donor‐acceptor complexes [μ‐(1,4‐dioxane){MCl₃(N₃S₂)}₂] which are characterized by IR spectroscopy. With excess 1,4‐dioxane the molybdenum compound forms the complex [MoCl₃(N₃S₂)(1,4‐dioxane)₂] in which, according to the crystal structure determination, one of the dioxane molecules coordinates at the molybdenum atom, the other one at one of the sulfur atoms of the cyclo‐thiazeno ring. The μ‐(NSN^2–) complex [Mo₂Cl₂(μ‐NSN)₂(μ‐O)(NCMe₃)(OCMe₃)₂]₂ has been obtained by the reaction of [MoN(OCMe₃)₃] with trithiazyle chloride in carbontetrachloride solution. According to the crystal structure determination this compound forms centrosymmetric dimeric molecules via two of the nitrogen atoms of two of the μ‐(NSN) groups to give a Mo₂N₂ fourmembered ring. [MoCl₃(N₃S₂)(1,4‐dioxane)₂]: Space group P2₁/c, Z = 4, lattice dimensions at –70 °C: a = 1522.9(2); b = 990.3(1); c = 1161.7(1) pm; β = 106.31(1)°, R₁ = 0.0317. [Mo₂Cl₂(μ‐NSN)₂(μ‐O)(NCMe₃)(OCMe₃)₂]₂ · 4 CCl₄: Space group P2₁/c, Z = 2, lattice dimensions at –83 °C: a = 1216.7(1); b = 2193.1(2); c = 1321.8(1) pm; β = 98.23(1)°; R₁ = 0.0507.     

Sn3N4, ein Zinn(IV)-nitrid – Synthese und erste Strukturbestimmung einer binären Zinn–Stickstoff-Verbindung

Sn₃N₄, a Tin(IV) Nitride – Syntheses and the First Crystal Structure Determination of a Binary Tin-Nitrogen Compound By reaction of SnI₄ with KNH₂ in liquid ammonia at 243 K a white product mixture was obtained. After evaporation of ammonia the solid residue was annealed in vacuum for 2–5 d at 573 K. Subsequently collected x-ray powder diffraction patterns exhibited reflections of KI and a new compound Sn₃N₄. Analogous reactions of SnBr₂ and KNH₂ led to KBr and dark brown microcrystalline Sn₃N₄ but also to metallic tin. The structure of tin(IV)-nitride was determined from X-ray and neutron powder diffraction data: Space group Fd 3 m, Z = 8, a = 9.037(3) Å. Sn₃N₄ crystallizes in a spinel type structure. Both metal atom positions are occupied by tin atoms of oxidation state plus four.     

Synthese und Struktur der Nitridoborat‐Nitride Ln4(B2N4)N (Ln = La,Ce) des Formeltyps Ln3+x(B2N4)Nx (x = 0, 1, 2)

Synthesis and Structure of Nitridoborate Nitrides Ln₄(B₂N₄)N (Ln = La, Ce) of the Formula Type Ln_3+x(B₂N₄)N_x (x = 0, 1, 2) The missing member of the formula type Ln_3+x(B₂N₄)N_x with x = 1 was synthesized and characterized for Ln = La and Ce. According to the single‐crystal X‐ray structure solution Ce₄(B₂N₄)N crystallizes in the space group C2/m (Z = 2) with the lattice parameters a = 1238.2(1) pm, b = 357.32(3) pm, c = 905.21(7) pm and β = 129.700(1)°. The anisotropic structure refinement converged at R1 = 0.039 and wR2 = 0.099 for all independent reflections. A powder pattern of La₄(B₂N₄)N was indexed isotypically with a = 1260.4(1) pm, b = 366.15(3) pm, c = 919.8(1) pm and β = 129.727(6)°. A structure rational for nitridoborates and nitridoborate nitrides containing B₂N₄ ions with the general formula Ln_3+x(B₂N₄)N_x with x = 0, 1, 2 is presented.     

Die Kristallstrukturen der Azido‐Platinate (AsPh4)2[Pt(N3)4] und (AsPh4)2[Pt(N3)6]

Crystal Structures of the Azido Platinates (AsPh₄)₂[Pt(N₃)₄] and (AsPh₄)₂[Pt(N₃)₆] The crystal structures of the two homoleptic azido platinates (AsPh₄)₂[Pt(N₃)₄] ( 1 ) and (AsPh₄)₂[Pt(N₃)₆] ( 2 ) were determined by X‐ray diffraction at single crystals. In 1 the [Pt(N₃)₄]^2– ions are without crystallographic site‐symmetry, and the platinum atoms show a planar surrounding. The [Pt(N₃)₆]^2– ions in 2 are centrosymmetric (C_i) with an octahedral surrounding at the platinum atoms. While 1 is highly explosive, 2 is of significantly greater stability. This behaviour is explained by the packing conditions. 1 : Space group P2₁/n, Z = 6, lattice dimensions at –80 °C: a = 1045.3(1), b = 1620.2(1), c = 4041.0(3) pm; β = 96.70(1)°; R₁ = 0.0654. 2 : Space group P1, Z = 1, lattice dimenstions at –80 °C: a = 1027.6(1), b = 1049.1(2), c = 1249.9(3) pm; α = 88.27(1)°, β = 74.13(1)°, γ = 67.90(1)°; R₁ = 0.0417.     

ChemInform Abstract: Temperature Induced Phase Transition of CaMn0.5Zr1.5(PO4)3 Phosphate.

In view of a known structural phase transition at 800—875 °C and the by 10 times increased luminescence of Mn²⁺ in the high‐temperature phase, low‐ (LT) and high‐temperature (HT) polymorphs of CaMn_0.5Zr_1.5(PO₄)₃ are prepared by sol—gel reaction of Mn(O‐Ac)₂, Ca(NO₃)₂, ZrOCl₂, and NH₄H₂PO₄ in ethylene glycol followed by a final annealing (700 or 900 °C, 20 h, resp.).     

Copper(II)‐Catalyzed Synthesis of N‐Substituted‐3‐amino‐4‐cyano‐isoquinoline‐1(2H)‐ones by the Reaction of N‐Substituted‐2‐iodobenzamides with Malononitrile

A novel Cu(OAc)₂·H₂O catalyzed coupling reaction of N‐substituted‐2‐iodobenzamides with malononitrile to afford N‐substituted‐3‐amino‐4‐cyano‐isoquinoline‐1(2H)‐ones is described. The reaction proceeded in DMSO at 90°C for 5 h in nitrogen without external ligands.     

Über das metallreiche Lanthannitridoboratnitrid La5(B2N4)N2

On the Metal‐rich Lanthanum Nitridoborate Nitride La₅(B₂N₄)N₂ La₅(B₂N₄)N₂ was synthesized by solid state reactions in fused tantalum containers from Li₃(BN₂), LaCl₃, Li₃N and La at 950 °C. The crystal structure refinement on a needle‐shaped single‐crystal yielded the monoclinic space group C2/m, the lattice parameters a = 1259.5(2), b = 368.53(4), c = 909.4(2) pm, β = 106.03(2)°, and R values of R1 = 0.041, wR2 = 0.066 for all independent reflections. The new compound La₅(B₂N₄)N₂ introduces the member with x = 2 to the formula type RE_3+x(B₂N₄)N_x (RE = rare earth, x = 0, 1). The structure contains the nitridoborate ion B₂N₄^8– that is isoelectronic with the oxalate ion and N^3–. Corresponding with (La³⁺)₅(B₂N₄)^8–(N^3–)₂(e^–) one additional electron is present.     

N(B(NMe2)2)(Si(NMe2)3)(Ti(NMe2)3), [N(Si(NMe2)3)(Ti(NMe2)2)]2 und N(SiMe3)(Si(NMe2)3)(Ti(NMe2)3) — Synthese und Charakterisierung neuer molekularer Einkomponentenvorläufer für nitridische und carbonitridische Keramiken

N(B(NMe₂)₂)(Si(NMe₂)₃) (Ti(NMe₂)₃), [N(Si(NMe₂)₃)(Ti(NMe₂)₂)]₂ und N(SiMe₃)(Si(NMe₂)₃)(Ti(NMe₂)₃) — Synthesis and Characterization of New Molecular Single-source Precursors for Nitride and Carbonitride Ceramics Synthesis and spectroscopic data of the title compounds are reported. [N(Si(NMe₂)₃)(Ti(NMe₂)₂)]₂ crystallizes in the space group P1 , a = 8.406(7), b = 10.673(8), c = 10.872(6) Å, α = 68.45(4)°, β = 71.72(4)°, γ = 78.11(7)°, 2 877 diffractometer data (F_o ? 2σF_o), R = 0.051. The compound is characterized by a planar four-membered Ti₂N₂-ring with exocyclic tris(dimethylamino)silyl substituents attached to the nitrogen atoms of the ring.     

Syntheses and Structures of S4N4(OCH3)2 and CH3OS4N4(O)Cl

The reaction of S₄N₄Cl₂ with CH₃OH gives S₄N₄(OCH₃)₂, a simple dimethoxoderivative of S₄N₄. Its overall geometry is analogous to other compounds of the S₄N₄X₂ type. The chlorination of S₄N₄(OCH₃)₂ leads to the oxidation of one sulfur atom to S^VI and CH₃OS₄N₄(O)Cl is formed. The compounds were characterized by ir spectroscopy and their crystal structures were determined from single crystal diffraction data collected at ?153°C. The presence of S^VI in the molecule of CH₃OS₄N₄(O)Cl is manifested by a marked shortening of the bonds formed by this atom as compared with S₄N₄Cl₂ and S₄N₄(OCH₃)₂.     

Sol‐Gel‐Process in the Ammono‐System – a Novel Access to Silicon Based Nitrides

Controlled coammonolysis of elementalkylamides in aprotic organic solvents at low temperatures have been shown to result in the formation of polyazanes. The synthetic procedure developed may be addressed as “sol‐gel‐route in the ammono system”. Pyrolysis of these novel polymer precursors gave access to multinary nitrides. For the model systems Si(NHMe)₄/B(NMe₂)₃, Si(NHMe)₄/Ti(NMe₂)₄, and Si(NHMe)₄/Ta(NMe₂)₅ polymeric boro‐, titano and tantalosilazanes were obtained. Pyrolysis in ammonia at 1000 °C yielded amorphous silicon boron nitride, silicon titanium nitride and silicon tantalum nitride powders; further heating of the nitride powders at 1500 °C in nitrogen atmosphere led to the formation of partly crystalline composites of α‐Si₃N₄ and amorphous silicon boron nitride for the Si/B/N system, a composite of finely dispersed TiN and amorphous silicon titanium nitride for the Si/Ti/N system, and crystalline TaN and amorphous silicon nitride for the Si/Ta/N system. Furthermore, the structure and pyrolysis chemistry of the polymeric intermediates, as well as the morphology of the pyrolysis products, were studied by NMR, MAS‐NMR, FT‐IR, DTA‐TG‐MS, XRD, SEM, EDX and elemental analyses.     

Ein neues Samariumnitridsulfid: Sm4N2S3

A New Samarium Nitride Sulfide: Sm₄N₂S₃ The oxidation of samarium with sulfur in the presence of SmCl₃ and NaN₃ as nitrogen source (molar ratio: 12:9:4:2, evacuated silica vessel, some NaCl as flux, 850°C, 7 d) yields Sm₄N₂S₃ as lath-shaped, dark red single crystals. The by-products (NaCl and NaSm₂Cl₆) are rinsed with water from the crude product. The crystal structure of Sm₄N₂S₃ (monoclinic, C2/m (no. 12), Z = 2, a = 1 318.04(12), b = 391.57(2), c = 1 031.76(9) pm, β = 130.874(6)°, R = 0.036, R_w = 0.031) contains two crystallographically different Sm³⁺, both in sixfold coordination of the anions. Besides distorted octahedra [(Sm1)N₃S₃] and [(Sm2)NS₅], tetrahedra [(N^3?)(Sm)] connected via two cis-oriented edges to form chains [N(Sm1)_3/3(Sm2)_1/1]³⁺ build up the Mayn structural feature. These are arranged in the fashion of a closest packing of rods and held together by two crystallographically different S^2? anions which take care for charge neutrality and three-dimensional interconnection.     

Synthesis and characterization of poly(aminoborane) as a new boron nitride precursor

During the solution reaction of NaBH₄/(NH₄)₂SO₄ in tetraglyme to form borazine, polymeric aminoborane (NH₂BH₂)_x has been isolated as a white powder. The powder was characterized by thermal gravimetric analysis/differential scanning calorimetry, infrared and mass spectroscopies, and powder X‐ray diffraction. Solid‐state ¹⁵N and ¹¹B nuclear magnetic resonance firmly proved that the chain‐like poly(aminoborane) evolved a partially condensed B₃N₃ ring structure by dehydrogenative condensation between chains at 200 °C. Pyrolysis of the polymer in a nitrogen stream up to 1400 °C led to a 75% yield of hexagonal boron nitride with an interlayer spacing of 3.37 Å. Copyright © 1999 John Wiley & Sons, Ltd.     

High‐Pressure Synthesis of Metal–Inorganic Frameworks Hf4N20⋅N2, WN8⋅N2, and Os5N28⋅3 N2 with Polymeric Nitrogen Linkers

Polynitrides are intrinsically thermodynamically unstable at ambient conditions and require peculiar synthetic approaches. Now, a one‐step synthesis of metal–inorganic frameworks Hf₄N₂₀?N₂, WN₈?N₂, and Os₅N₂₈?3 N₂ via direct reactions between elements in a diamond anvil cell at pressures exceeding 100 GPa is reported. The porous frameworks (Hf₄N₂₀, WN₈, and Os₅N₂₈) are built from transition‐metal atoms linked either by polymeric polydiazenediyl (polyacetylene‐like) nitrogen chains or through dinitrogen units. Triply bound dinitrogen molecules occupy channels of these frameworks. Owing to conjugated polydiazenediyl chains, these compounds exhibit metallic properties. The high‐pressure reaction between Hf and N₂ also leads to a non‐centrosymmetric polynitride Hf₂N₁₁ that features double‐helix catena‐poly[tetraz‐1‐ene‐1,4‐diyl] nitrogen chains [?N?N?N=N?]_∞.     

Synthesis,Crystal Structure and Properties of Rubidium Dihydrogentricyanomelaminate Semihydrate Rb[H2C6N9] · 1/2 H2O

Rubidium dihydrogentricyanomelaminate semihydrate Rb[H₂C₆N₉] · ¹/₂ H₂O was obtained as colorless rod‐like single crystals from a solution of Rb₃[C₆N₉] · H₂O and 0.1 M HCl after water evaporation at room temperature. According to the X‐ray single‐crystal structure determination (Rb[H₂C₆N₉] · ¹/₂ H₂O: C2/c (no. 15), a = 2007.4(3) pm, b = 512.2(1) pm, c = 2168.0(4) pm, β = 111.66(2)°, Z = 8, R1 = 0.059, 2391 independent reflections, 159 parameters) Rb⁺ and cyclic planar [H₂C₆N₉]^— ions as well as hydrate water molecules occur in the crystal. Rb[H₂C₆N₉] · ¹/₂ H₂O was investigated by FTIR and Raman spectroscopy, TG measurements and temperature‐dependent X‐ray powder diffraction. According to the thermoanalytic investigations, dehydration of Rb[H₂C₆N₉] · ¹/₂ H₂O starts above 60 °C and is finished below 250 °C.     

New Ternary Hafniumhalides: Cs[Hf2Br9] and Rb[Hf2Br9]

The syntheses and crystal structures of two new ternary hafnium compounds, Cs[Hf₂Br₉] ( 1 ) and Rb[Hf₂Br₉] ( 2 ), are described. Both compounds are obtained in high yield from the chemical reaction of HfBr₄ and CsBr or RbBr, respectively, in the presence of a small amount of elemental Al at 450 °C in sealed silica tubes. They crystallize isostructurally in the monoclinic space group P2/n. The lattice parameters are a = 9.946(1) ( 1 ) and 9.9388(4) Å ( 2 ), b = 6.6580(9) ( 1 ) and 6.6695(3) Å ( 2 ), c = 12.930(2) ( 1 ) and 12.8435(6) Å ( 2 ), and β = 112.479(6)° ( 1 ) and 112.726(2)° ( 2 ). The crystals of the two compounds contain dinuclear tri‐μ‐bromido‐hexabromido‐dihafnate(–) complex anions, [Hf₂Br₉]^–, besides the alkali metal cations. The complex anions can be described as face‐sharing bioctahedral units.     

Glycol modified cis -diisopropoxy- bis ( N -phenylsalicylideneiminato)zirconium(IV): syntheses,characterization and low temperature transformation to nanocrystalline zirconia

Zr(OPrⁱ)₄·PrⁱOH reacts with N-phenylsalicylideneimine in anhydrous benzene in 1 : 2 molar ratio to afford [Zr{O(C₆H₄)CH=NPh}₂{OPrⁱ}₂] (1). Further reactions of 1 with various glycols yield heteroleptic complexes of the type [Zr{O(C₆H₄)CH=NPh}₂{O–G–O}] [where–G–= (CH₂)₂ (2), (CH₂CHCH₃) (3), (CH₃CHCHCH₃) (4), (CH₂CHC₂H₅) (5), (CH₂)₃ (6), (CH₂CH₂CHCH₃) (7), and (CH₂)₆ (8)]. All new derivatives have been characterized by elemental analyses, FTIR and NMR (¹H and ¹³C{¹H}) studies. FAB mass spectra of 1 and 7 revealed the monomeric nature of these complexes. Complete hydrolyses and low temperature transformations of 1 and 7 using Sol-Gel technique formed tetragonal phase of ZrO₂ at 700°C, whereas transformation of tetragonal to monoclinic phase occurred at 900°C. SEM observations of these samples indicate formation of agglomerates of nanocrystalline zirconia (Scherer analysis).