Synthesis and crystal structures of zirconium(IV) nitrate complexes (NO2)[Zr(NO3)3(H2O)3]2(NO3) 3, Cs[Zr(NO3)5], and (NH4)[Zr(NO3)5](HNO3)

The zirconium nitrate complexes (NO₂)[Zr(NO₃)₃(H₂O)₃]₂(NO₃)₃ (1), Cs[Zr(NO₃)₅] ((2), (NH₄)[Zr(NO₃)₅](HNO₃) (3), and (NO₂)_0.23(NO)_0.77[Zr(NO₃)₅] ((4) were prepared by crystallization from nitric acid solutions in the presence of H₂SO₄ or P₂O₅. The complexes were characterized by X-ray diffraction. The crystal structure of 1 consists of nitrate anions, nitronium cations, and [Zr(NO₃)₃(H₂O)₃]⁺ complex cations in which the Zr^IV atom is coordinated by three water molecules and three bidentate nitrate groups. The coordination polyhedron of the Zr^IV atom is a tricapped trigonal prism formed by nine oxygen atoms. The island structures of 2 and 3 contain [Zr(NO₃)₅]^? anions and Cs⁺ or NH₄ ⁺ cations, respectively. In addition, complex 3 contains HNO₃ molecules. Complex 4 differs from (NO₂)[Zr(NO₃)₅] in that three-fourth of the nitronium cations in 4 are replaced by nitrosonium cations NO⁺, resulting in a decrease in the unit cell parameters. In the [Zr(NO₃)₅]^? anion involved in complexes 2–4, the Zr^IV atom is coordinated by five bidentate nitrate groups and has an unusually high coordination number of 10. The coordination polyhedron is a bicapped square antiprism.     

Crystal Structure of the Mixed‐Valent Basic Mercury Nitrate HgI2(NO3)2·HgII(OH)(NO3)·HgII(NO3)2·4HgIIO [= Hg8O4(OH)(NO3)5]

Light‐yellow single crystals of the mixed‐valent mercury‐rich basic nitrate Hg₈O₄(OH)(NO₃)₅ were obtained as a by‐product at 85 °C from a melt consisting of stoichiometric amounts of (Hg^I₂)(NO₃)₂·2H₂O and Hg^II(OH)(NO₃). The title compound, represented by the more detailed formula Hg^I₂(NO₃)₂·Hg^II(OH)(NO₃)·Hg^II(NO₃)₂·4Hg^IIO, exhibits a new structure type (monoclinic, C2/c, Z = 4, a = 6.7708(7), b = 11.6692(11), c = 24.492(2) Å, β = 96.851(2)°, 2920 structure factors, 178 parameters, R1[F² > 2σ(F²)] = 0.0316) and is made up of almost linear [O‐Hg^II‐O] and [O‐Hg^I‐Hg^I‐O] building blocks with typical Hg^II‐O distances around 2.06Å and a Hg^I‐O distance of 2.13Å. The Hg₂²⁺ dumbbell exhibits a characteristic Hg‐Hg distance of 2.5079(7) Å. The different types of mercury‐oxygen units form a complex three‐dimensional network exhibiting large cavities which are occupied by the nitrate groups. The NO₃^? anions show only weak interactions between the nitrate oxygen atoms and the mercury atoms which are at distances > 2.6Å from one another. One of the three crystallographically independent nitrate groups is disordered.     

Synthesis and Crystal Structure of Alkali Metal and Ammonium Nitratocuprates(II): M3[Cu(NO3)4](NO3) (M = K,NH4, Rb) and Cs2[Cu(NO3)4]

Blue crystals of metal nitratocuprates(II), M₃[Cu(NO₃)₄](NO₃) (M = K ( I ), NH₄ ( II ), Rb ( III )) and Cs₂[Cu(NO₃)₄] ( IV ) were synthesized from Cu(NO₃)₂ · 3 H₂O and MNO₃ by heating at 100–140 °C during 3–12 h. X-ray single crystal structures for isotypic I and II reveal the presence of the [Cu(NO₃)₄]^2– and NO₃^– anions and M⁺ cations. Structure IV contains [Cu(NO₃)₄]^2– and Cs⁺. In structures I , II , and IV , Cu atoms have a square-planar coordination [CuO₄] with short Cu–O distances of 1.92–2.00 Å, the oxygen atoms belonging to four different NO₃ groups. Each coordinated NO₃ group is a nonsymmetrical bidentate ligand with the second, longer Cu–O distance from 2.38 to 2.74 Å. Rubidium derivative III was shown to be isotypic to I on the basis of unit cell dimensions and symmetry. Eight-coordinate metal(II) environment in tetranitrates is compared for transition metals with different electronic configurations.     

Synthesis and X-Ray Structure of New Copper(II) Nitrates: Cu(NO3)2 · H2O and β-modification of Cu(NO3)2

Blue crystals of a Cu(NO₃)₂ · H₂O were synthesized by interaction of CuO with boiling 100% HNO₃. Stable β-Cu(NO₃)₂ modification was obtained by the sublimation of copper(II) nitrate in evacuated ampoule over the 150→100°C temperature gradient for 24 hr. According to X-Ray single crystal analysis Cu(NO₃)₂ · H₂O is monoclinic with a = 6.377(1), b = 8.548(1), c = 9.769(1) Å, β = 100.41(1)°, Z = 4, and space group P2₁/c. β-modification Cu(NO₃)₂ is orthorhombic with a = 14.161(5), b = 7.516(3), c = 12.886(2) Å, Z = 12, and space group Pbcn. In the both structures Cu atoms are square coordinated by 4 O atoms at the distances ranging from 1.92 to 2.02 Å. In each structure there are also additional Cu? O bonds with the distance of 2.33 or 2.35 Å and some weaker ones with the distances in the range of 2.65–2.72 Å. In the Cu(NO₃)₂ · H₂O structure the [CuO₄] squares are connected by the bridging NO₃ groups into zigzag chains, which are linked into layers by the longer Cu? O bonds. In the β-Cu(NO₃)₂ structure the [CuO₄] fragments of two types are joined by the bridging NO₃ groups in a three-dimensional framework. Some correlations were found between N? O distances and coordination functions of O atoms.     

Hydrate isomerism in [Cu(en)2(H2O)1.935]2[Fe(CN)6]·4H2O

The title compound, bis[di­aqua­bis­(ethyl­enedi­amine‐κ²N,N′)copper(II)­] hexa­cyano­iron(II) tetrahydrate, [Cu(C₂H₈N₂)₂(H₂O)_1.935]₂[Fe(CN)₆]·4H₂O, was crystallized from an aqueous reaction mixture initially containing CuSO₄, K₃[Fe(CN)₆] and ethyl­enedi­amine (en) in a 3:2:6 molar ratio. Its structure is ionic and is built up of two crystallographically different cations, viz. [Cu(en)₂(H₂O)₂]²⁺ and [Cu(en)₂(H₂O)_1.87]²⁺, there being a deficiency of aqua ligands in the latter, [Fe(CN)₆]⁴⁻ anions and disordered solvent water mol­ecules. All the metal atoms lie on centres of inversion. The Cu atom is octahedrally coordinated by two chelate‐bonded en mol­ecules [mean Cu—N = 2.016 (2) Å] in the equatorial plane, and by axial aqua ligands, showing very long distances due to the Jahn–Teller effect [mean Cu—O = 2.611 (2) Å]. In one of the cations, significant underoccupation of the O‐atom site is observed, correlated with the appearance of a non‐coordinated water mol­ecule. This is interpreted as the partial contribution of a hydrate isomer. The [Fe(CN)₆]⁴⁻ anions form quite regular octahedra, with a mean Fe—C distance of 1.913 (2) Å. The dominant intermolecular interactions are cation–anion O—H⋯N hydrogen bonds and these inter­actions form layers parallel to (001).     

Single Crystal Growth and Crystal Structure of Anhydrous Mercury(I) Nitrate,Hg2(NO3)2

Polycrystalline anhydrous Hg₂(NO₃)₂ was prepared by drying Hg₂(NO₃)₂·2H₂O over concentrated sulphuric acid. Evaporation of a concentrated and slightly acidified mercury(I) nitrate solution to which the same volumetric amount of pyridine was added, led to the growth of colourless rod‐like single crystals of Hg₂(NO₃)₂. Besides the title compound, crystals of hydrous Hg₂(NO₃)₂·2H₂O and the basic (Hg₂)₂(OH)(NO₃)₃ were formed as by‐products after a crystallization period of about 2 to 4 days at room temperature. The crystal structure was determined from two single crystal diffractometer data sets collected at —100°C and at room temperature: space group P2₁, Z = 4, —100°C [room temperature]: a = 6.2051(10) [6.2038(7)]Å, b = 8.3444(14) [8.3875(10)]Å, c = 11.7028(1) [11.7620(14)]Å, ß = 93.564(3) [93.415(2)]°, 3018 [3202] structure factors, 182 [182] parameters, R[Fμ² > 2σ(Fμ²)] = 0.0266 [0.0313]. The structure is built up of two crystallographically inequivalent Hg₂²⁺ dumbbells and four NO₃^— groups which form molecular [O₂N‐O‐Hg‐Hg‐O‐NO₂] units with short Hg‐O bonds. Via long Hg‐O bonds to adjacent nitrate groups the crystal packing is achieved. The Hg‐Hg distances with an average of d(Hg‐Hg) = 2.5072Å are in the typical range for mercurous oxo compounds. The oxygen coordination around the mercury dumbbells is asymmetric with four and six oxygen atoms as ligands for the two mercury atoms of each dumbbell. The nitrate groups deviate slightly from the geometry of an equilateral triangle with an average distance of d(N‐O) = 1.255Å.     

Anhydrous Nitrates and Nitrosonium Nitratometallates of Manganese and Cobalt,M(NO3)2, NO[Mn(NO3)3], and (NO)2[Co(NO3)4]: Synthesis and Crystal Structure

Crystalline NO[Mn(NO₃)₃] ( I ) and (NO)₂[Co(NO₃)₄] ( II ) were synthesized by reaction of the corresponding metal and a liquid N₂O₄/ethylacetate mixture. I is orthorhombic, Pca2₁, a = 9.414(2), b = 15.929(3), c = 10.180(2) Å, Z = 4, R₁ = 0.0286. II is monoclinic, C2/c, a = 14.463(3), b = 19.154(4), c = 13.724(3) Å, β = 120.90(3), Z = 12, R₁ = 0.0890. Structure I consists of [Mn(NO₃)₃]^– sheets with NO⁺ cations between them. Two types of Mn atoms have CN_Mn = 7 and 8. Structure II is ionic containing isolated [Co(NO₃)₄]‐anions and NO⁺ cations with CN_Co = 8. Crystals of Mn(NO₃)₂ ( III ) and Co(NO₃)₂ ( IV ) were obtained by concentration of metal nitrate hydrate solutions in 100% HNO₃ in a desiccator with P₂O₅. III is cubic, Pa 3, a = 7.527(2) Å, Z = 4, R₁ = 0.0987. IV is trigonal, R 3, a = 10.500(2), c = 12.837(3) Å, Z = 12, R₁ = 0.0354. The three dimensional structure III is isotypic to the strontium and barium dinitrates. Structure IV contains a three dimensional network of interconnected Co(NO₃)_6/3 units with a distorted octahedral coordination environment of Co atoms. General correlations between central atom coordination and coordination modes of NO₃ groups are discussed.     

Three-layered close packing in the crystal structure of tris(ethylenediamine)cobalt(III) hexanitrorhodate(III) hydrate, [Co(en)3][Rh(NO2)6]·3H2O,en=C2H8N2

In the structure of cubic tris(ethylenediamine)cobalt(III) hexanitrorhodate(III) hydrate, [Co(en)₃][Rh(NO₂)₆]·3H₂O, en=C₂H₈N₂, with a=16.540(5) Å, space group Pa3 (nonstandard, reduced to orthorhombic Pcab), the complex cations, anions, and water molecules are arranged by the law of three-layered (fcc) close packing of “quasispherical” species according to two structural types, NaCl and CaF₂. The packing is formed of [Rh(NO₂)₆]^3? anions, which also fill the octahedral voids. The tetrahedral voids are occupied by the central atoms of the [Co(en)₃]³⁺ cations, and the H₂O molecules lie between the cations, performing the packing function: the Ow...N_en contacts of 3.04 Å and the Ow..O_{NO 2} contacts of 3.01 Å characterize weak van der Waals interactions. The values of the interatomic distances Co?N, Rh?N, N?O, N?C, and C?C are in good agreement with the known data.     

Disordering of the [NbOF5]2− complex anions in bis(glycinium) pentafluoridooxidoniobate(V) and bis(β‐alaninium) pentafluoridooxidoniobate(V) dihydrate

The title compounds, (C₂H₆NO₂)₂[NbOF₅], (I), and (C₃H₈NO₂)₂[NbOF₅]·2H₂O, (II), are built from isolated distorted octahedral [NbOF₅]²⁻ complex anions, amino acid cations and water molecules [for (II)]. In the pentafluoridooxidoniobate(V) anions, the Nb and O atoms, and the F atoms in trans positions with respect to the O atoms, are disordered about an inversion centre for both structures. The Nb atoms are shifted from the inversion centres by distances of 0.1455 (1) and 0.1263 (2) Å for (I) and (II), respectively. The Nb=O and Nb—F(trans) bond lengths are 1.7952 (3) and 2.0862 (3) Å, respectively, for (I), and 1.8037 (7) and 2.0556 (7) Å for (II). In the crystal structures, cations and water molecules [for (II)] are linked to the [NbOF₅]²⁻ anions via hydrogen bonds. This study demonstrates the possibility of true geometry determination of disordered [NbOF₅]²⁻ complex anions in centrosymmetric structures.     

K2[Hg(SO3)2]·2.25H2O

The characteristic feature of the structure of the title compound, dipotassium bis(sulfito‐κS)mercurate(II) 2.25‐hydrate, is a layered arrangement parallel to (001) where each of the two independent [Hg(SO₃)₂]²⁻ anions are grouped into centrosymmetric pairs and are surrounded by two K⁺ cations to give the overall layer composition {K₂[Hg(SO₃)₂]₂}²⁻. The remaining cations and the uncoordinated water molecules are situated between these layers. Within the [Hg(SO₃)₂]²⁻ anions, the central Hg atoms are twofold coordinated by S atoms, with a mean Hg—S bond length of 2.384 (2) Å. The anions are slightly bent [174.26 (3) and 176.99 (3)°] due to intermolecular O...Hg interactions greater than 2.8 Å. All coordination polyhedra around the K⁺ cations are considerably distorted, with coordination numbers ranging from six to nine. Although the H atoms of the five water molecules (one with symmetry 2) could not be located, O...O separations between 2.80 and 2.95 Å suggest a system of medium to weak O—H...O hydrogen bonds which help to consolidate the structural set‐up. Differences and similarities between the bis(sulfito‐κS)mercurate(II) anions in the title compound and those in the related salts (NH₄)₂[Hg(SO₃)₂] and Na₂[Hg(SO₃)₂]·H₂O are discussed.     

Synthesis and Crystal Structure of Cesium Nitratometalates(II), Cs2[M(NO3)4] (M = Mn,Co, Ni,Zn)

Crystalline cesium nitratometalates(II), Cs₂[M(NO₃)₄] (M = Mn ( I ), Co ( II ), Ni ( III ), and Zn ( IV )) were synthesized from M(NO₃)₂ · n H₂O and CsNO₃ by heating at 80–120 °C over 10–12 h. According to X-ray crystal structure analysis, the compounds are built from Cs⁺ cations and [M(NO₃)₄]^2– anions. The latter differ by the type of metal coordination: a dodecahedron for Mn in I (CN = 8, r_Mn–O 2.24–2.37 Å), a seven coordination for Co in II (CN = 4 + 3, r_Co–O 2.03–2.16 Å and 2.21–2.35 Å) and a tetrahedral distorted dodecahedron for Zn in IV (CN = 4 + 4, r_Zn–O 1.98–2.15 Å and 2.38–2.72 Å). Ni atom in III has a distorted octahedral NiO₆ environment provided by two unidentate and two bidentate NO₃ groups with Ni–O distances of 2.01–2.14 Å. The differences in metal coordination are discussed in terms of valence electron configurations, ionic radii, and the packing effects.     

Synthesis and Crystal Structure of [La(phen)2(H2O)2(NO3)2]NO3 · 2(phen)(H2O) with phen = 1,10‐phenanthroline

The title compound [La(phen)₂(H₂O)₂(NO₃)₂](NO₃) · 2(phen)(H₂O) with phen = 1,10‐phenanthroline was prepared by the stoichiometric reaction of La(NO₃)₃ · 6 H₂O and 1,10‐phenanthroline monohydrate in a CH₃OH–H₂O solution. The crystal structure (triclinic, P 1 (no. 2), a = 11.052(2), b = 13.420(2), c = 16.300(2) Å, α = 78.12(1)°, β = 88.77(1)°, γ = 83.03(1)°, Z = 2, R = 0.0488, wR² = 0.1028) consists of [La(phen)₂(H₂O)₂(NO₃)₂]²⁺ complex cations, NO₃^– anions, phen and H₂O molecules. The La atom is 10‐fold coordinated by four N atoms of two bidentate chelating phen ligands and six O atoms of two H₂O molecules and two bidentate chelating NO₃^2– ligands with d(La–O) = 2.522–2.640 Å and d(La–N) = 2.689–2.738 Å. The intermolecular π‐π stacking interactions play an essential role in the formation of two different 2 D layers parallel to (001), which are formed by complex cations and uncoordinating phen molecules, respectively. The uncoordinated NO₃^– anions and H₂O molecules are sandwiched between the cationic and phen layers.     

New iron(III) nitrate hydrates: Fe(NO3)3·xH2O with x = 4, 5 and 6

Crystals of the title compounds were grown from their hydrous melts or solutions. The crystal structure of iron(III) trinitrate hexahydrate {hexaaquairon(III) trinitrate, [Fe(H₂O)₆](NO₃)₃} is built up from [Fe(H₂O)₆]²⁺ octahedra and nitrate anions connected via hydrogen bonds. In iron(III) trinitrate pentahydrate {pentaaquanitratoiron(III) dinitrate, [Fe(NO₃)(H₂O)₅](NO₃)₂}, one water molecule in the coordination octahedron of the Fe^III atom is substituted by an O atom of a nitrate group. Iron(III) trinitrate tetrahydrate {triaquadinitratoiron(III) nitrate monohydrate, [Fe(NO₃)₂(H₂O)₃]NO₃·H₂O} represents the first example of a simple iron(III) nitrate with pentagonal–bipyramidal coordination geometry, where two bidentate nitrate anions and one water molecule form a pentagonal plane.     

Synthesis and crystal structure of New Amminecopper(II) Nitrates: [Cu(NH3)2](NO3)2 and [Cu(NH3)](NO3)2

[Cu(NH₃)₂](NO₃)₂ ( I ) and [Cu(NH₃](NO₃)₂ ( II ) were synthesized by interaction of molten NH₄NO₃ with [Cu(NH₃)₄](NO₃)₂ and Cu(NO₃)₂ · 3 H₂O, respectively, at 180 to 195°C for 24 hr. According to X-Ray single crystal analysis, I is orthorhombic (sp. gr. Pbca) with a = 5.678(1), b = 9.765(2), c = 11.596(2) Å, Z = 4, R = 0.060; II is monoclinic (sp. gr. P2₁/c) with a = 6.670(1), b = 8.658(2), c = 9.661(2) Å, β = 101.78(2)°, Z = 4, R = 0.027. In both structures, the nearest coordination environment of Cu is a slightly distorted square formed by N (from NH₃) and O atoms (from NO₃ groups). The structure of I consists of centrosymmetrical [Cu(NH₃)₂](NO₃)₂ molecules linked by hydrogen bonds. The Cu? N and Cu? O distances are 1.98 and 2.01 Å, respectively. In II , the Cu? N distance is 1.95 Å, the Cu? O distances are 1.96, 2.02, and 2.03 Å. The [CuO₃NH₃] squares are connected by NO₃ bridges into zigzag chains, which are linked into layers by longer Cu? O interactions (2.31 Å). Obviously, the layers are additionally strengthened and held together by hydrogen bonds.     

Synthese,Struktur und Thermolyse der ternären Ammoniumnitrate (NH4)3[M2(NO3)(9] (M  La?Gd)

Synthesis, Structure, and Thermolysis of the (NH₄)₃[M₂(NO₃)₉] (M ? La? Gd) The ternary ammonium nitrates (NH₄)₃[M₂(NO₃)₉] (M ? La-Gd) are obtained as single crystals from a solution of the respective sesquioxides in a melt of NH₄NO₃ and sublimation of the excess NH₄NO₃. In the crystal structure of (NH₄)₃[Pr₂(NO₃)₉] (cubic, P4₃32, Z = 4, a = 1 377.0(1) pm, R = 0.038, R_w = 0.023) Pr³⁺ is surrounded by six bidentate nitrate ligands of which three are bridging to neighbouring Pr³⁺ ions. This results in a branched folded chain, held together by the NH₄⁺ ions which occupy cavities in the structure. (NH₄)₃[Pr₂(NO₃)₉] is the first intermediate product of the thermal decomposition of (NH₄)₂[Pr(NO₃)₅(H₂O)₂] · 2H₂O.     

Triaqua(2,2′‐bipyridine‐κ2N,N′)(nitrato‐κO)manganese(II) nitrate

The crystal structure of the title compound, [Mn(NO₃)(C₁₀H₈N₂)(H₂O)₃]NO₃, contains a monomeric [Mn(NO₃)(bpy)(H₂O)₃]⁺ cation (bpy is 2,2′‐bi­pyridine) and a nitrate anion. The Mn^II ion is coordinated by one chelating bpy [Mn—N 2.241 (3) and 2.259 (3) Å], three water mol­ecules [Mn—O 2.120 (3)–2.188 (3) Å] and a nitrate ligand [Mn—O 2.228 (2) Å] in a distorted octahedral geometry. There are O?H—O hydrogen‐bonding interactions between the ligated water mol­ecules and the ligated and unligated nitrate anions, resulting in double columns of stacked cations and anions.     

Synthesis and structure of copper(II) trans-diaqua-bis(3-hydroxybenzoylhydrazine) nitrate dihydrate [Cu(C7H8O2N2)2(OH2)2](NO3)22H2O

Synthesis of [Cu(m-HBH)₂(OH₂)₂](NO₃)₂·2H₂O, where m-HBH = C₇H₈O₂N₂ (3-hydroxybenzoylhydrazine), is described. The structure of the compound was studied by X-ray phase analysis and IR spectroscopy; crystal data are a = 57.415(6) Å, b = 19.760(2) Å, c = 7.586(2) Å; Fdd 2, Z = 16, R(F) = 0.053. The compound consists of [Cu(m-HBH)₂(OH₂)₂]²⁺ complex cations, NO ₃ ^? anions, and two water molecules. The similarity between the IR spectra of Cu(m-HBH)₂(NO₃)₂·nH₂O and Co(m-HBH)₂(NO₃)₂·5H₂O, element analysis data, and crystal data obtained at the first stage of X-ray analysis show that the structures and compositions of these compounds are identical relative to the type of surroundings of the central atom. In contrast to the cobalt compound [Co(m-HBH)₂(OH₂)₂](NO₃)₂·3H₂O, in which the cobalt atom has a nearly regular octahedron as a coordination polyhedron, the copper(II) compound has a square bipyramid around the copper atom; c.n. is 6 = 4 + 2 (planar distances: 2.013(2) Å, 2.021(2) Å, 2.033(3) Å, 2.087(3) Å; axial distances: 2.367(3) Å, 2.374(3) Å) and lacks one crystallization water molecule.     

Structure of Hexakis(imidazole)nickel(II) Nitrate Water Solvate:[Ni(Im)_6] (NO_3)_2·4H_2O

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K2[O(HgSO3)3], a new sulfitomercurate with an [OHg3] core

The structure of dipotassium μ₃‐oxido‐tris[sulfitomercurate(II)], K₂[O(HgSO₃)₃], is characterized by segregation of the K⁺ cations and complex [O(HgSO₃)₃]²⁻ anions into layers parallel to (010). The anion has m symmetry and is a new example of a μ₃‐oxido‐trimercurate complex with a central [OHg₃] core. This unit adopts the shape of a flat, almost trigonal, pyramid (mean O—Hg = 2.072 Å and mean Hg—O—Hg = 110.8°). The two independent Hg—S bonds have nearly the same length (mean Hg—S = 2.335 Å). Due to intermolecular O...Hg donor–acceptor interactions greater than 2.65 Å, the O—Hg—S fragments are slightly bent. The [KO₉] coordination polyhedron of the K⁺ cation approaches a distorted tricapped trigonal prism with a [6+1+2] coordination.     

Crystal Structure and Thermal Behaviour of the Mixed‐Valent Basic Mercury Nitrate HgI2(OH)(NO3)·HgIIO

Single crystals of the hitherto unknown compound Hg₂(OH)(NO₃)·HgO were obtained unintentionally during hydrothermal phase formation experiments in the system Ag—Hg— As—O. Hg₂(OH)(NO₃)·HgO (orthorhombic, Pbca, Z = 8, a = 6.4352(8), b = 11.3609(14), c = 15.958(2) Å, 1693 structure factors, 83 parameters, R1[F² > 2σ(F²)] = 0.0431) adopts a new structure type and is composed of two types of mercury‐oxygen zig‐zag‐chains running perpendicular to each other and of intermediate nitrate groups. One type of chains runs parallel [010] and consists of (Hg—Hg—OH) units with a typical Hg—Hg distance of 2.5143(10) Å for the mercury dumbbell, whereas the other type of chains runs parallel [100] and is made up of (O—Hg—O) units with short Hg—O distances of about 2.02Å. Both types of chains are concatenated by a common O atom with a slightly longer Hg—O distance of 2.25Å. The three‐dimensional assembly is completed by nitrate groups whose O atoms show Hg—O distances > 2.80Å. Weak hydrogen bonding between the OH group and one oxygen atom belonging to the nitrate group stabilizes this arrangement. Hg₂(OH)(NO₃)·HgO decomposes above 200 °C to HgO.