Die Tetracyanoborsäuren H[B(CN)4]·n H2O,n = 0, 1, 2

The Tetracyanoboronic Acids H[B(CN)₄]·n H₂O, n = 0, 1, 2 Treatment of an aqueous solution of Na[B(CN)₄] with an acidic cation exchange resin leads to a solution of the strong tetracyanoboronic acid. Evaporation of the solution at room temperature yields colourless single crystals of [H₅O₂][B(CN)₄] ( , a = 9.5830(2) Å, c = 14.25440(3) Å, Z = 1). Further drying of [H₅O₂][B(CN)₄] (mp. 115 °C) in vacuum at 50 °C gives polycrystalline [H₃O][B(CN)₄] (P6₃mc, a = 8.704(1) Å, c = 6.152(1) Å, Z = 2), which is thermally stable up to 145 °C. The anhydrous polycrystalline acid H[B(CN)₄] is formed quantitatively by reacting Me₃SiNCB(CN)₃ with gaseous HCl. This acid starts to decompose at 190 °C with loss of HCN. All three acids were further characterized by vibrational spectroscopy, and elemental analysis.     

Synthesis,Vibrational Spectrum and Structure of the Tetracyanoborate K[B(CN)4]·CH3CN

The new tetracyanoborate K[B(CN)₄]·CH₃CN was synthesized by dissolution of the solvent‐free K[B(CN)₄] in acetonitrile and subsequent careful crystallization. The crystal structure has been determined by single‐crystal X‐ray diffraction. It crystallizes in the orthorhombic space group P2₁2₁2₁ with Z = 4. Some comparisons with related structures are made, and the vibrational spectrum is discussed.     

Darstellung,Kristallstruktur, thermischer Abbau und Schwingungsspektren von [Co(NH3)6]2[Be4O(CO3)6] · 10 H2O

Preparation, Crystal Structure, Thermal Decomposition, and Vibrational Spectra of [Co(NH₃)₆]₂[Be₄O(CO₃)₆] · 10 H₂O [Co(NH₃)₆]₂[Be₄O(CO₃)₆] · 10 H₂O is a suitable compound for the quantitative determination of beryllium. It can be obtained by reaction of aqueous solutions of carbonatoberyllate with [Co(NH₃)₆]Cl₃. The crystal structure (trigonal‐rhombohedral, R3c (Nr. 161), a = 1071,6(1) pm, c = 5549,4(9) pm, V_EZ = 5519(1) · 10⁶ pm³, Z = 6, R1(I ≥ 2σ(I)) = 0,037, wR2(I ≥ 2σ(I)) = 0,094) contains [Co(NH₃)₆]³⁺‐ and [Be₄O(CO₃)₆]^6–‐ions, which are directly hydrogen bonded as well as with water molecules. The complex cations and anions occupy the positions of a distorted anti‐CaF₂‐type. The thermal decomposition, IR and Raman spectra are presented and discussed.     

Darstellung und Kristallstrukturen der ersten Alkalimetall‐hexacarbonatooxotetraberyllate: K6[Be4O(CO3)6] · 7 H2O und K6[Be4O(CO3)6]

Preparation and Crystal Structures of the first Alkalimetall‐hexacarbonato‐oxotetraberyllates: K₆[Be₄O(CO₃)₆] · 7 H₂O and K₆[Be₄O(CO₃)₆] K₆[Be₄O(CO₃)₆] · 7 H₂O has been prepared by dissolving freshly precipitated Be(OH)₂ in an aqueous KHCO₃ solution. After enriching the title compound by extraction with ethanol the heptahydrate crystallizes from the organic phase (triklin, P1¯ (No. 2) with a = 951, 01(11), b = 958, 45(12), c = 1601, 7(2) pm, α = 79, 253(13)°, β = 78, 943(12)°, γ = 65, 119(12)°, V_EZ = 1290, 6(3)·10⁶ pm³, Z = 2). Thermal decomposition forms rhombohedral crystals of the anhydrous compound (trigonal‐rhombohedric, R3¯ (No. 148) with a = 1416, 42(6), c = 1704, 5(1) pm, V_EZ = 2961, 4(3)·10⁶ pm³, Z = 6).     

Synthesis,Crystal Structure,and Thermal Properties of the Energetic Coordination Compound [Co(DAT)2(H2O)4](HTNR)2·2H2O (DAT = 1,5‐diaminotetrazole)

A new coordination complex, [Co(DAT)₂(H₂O)₄](HTNR)₂ · 2H₂O [DAT = 1,5‐diaminotetrazole, HTNR = 2,4,6‐trinitroresorcinol (styphnic acid)], was obtained in high yield and characterized by elemental analysis and Fourier‐transform infrared (FT‐IR) spectroscopy. The molecular structure of [Co(DAT)₂(H₂O)₄](HTNR)₂ · 2H₂O in the crystalline state is determined by X‐ray crystallography is as follows: monoclinic, C2/c, a = 19.216(3) Å, b = 5.4992(8) Å, c = 30.418(5) Å, β = 104.500(5), V = 3112.0(8) ų, Z = 4, ρ_calc. = 1.851 g · cm^–3, R₁ = 0.0271 and wR₂ = (all data) 0.0674. The central cobalt(II) cation is coordinated by two nitrogen atoms of two DAT and four oxygen atoms of four H₂O ligand molecules to form a six‐coordinate and slightly distorted octahedral structure. Extensive intermolecular hydrogen bonds link molecular units of [Co(DAT)₂(H₂O)₄(HTNR)₂ · 2H₂O together to form a 3D net structure with pore canals. The thermal decomposition mechanism for the title compound was predicted based on DSC, TG‐DTG, and FT‐IR analyses and non‐kinetic parameters of the first exothermic process were estimated by applying the Kissinger, Starink, and Ozawa–Doyle methods.     

Synthesis,Crystal Structure and Magnetic Behaviour of {[Co(dimb)2(H2O)2]·(NO3)2·(H2O)2}n

The title complex {[Co(dimb)₂(H₂O)₂]·(NO₃)₂·(H₂O)₂}_n ( 1 ) (dimb = 1,3‐di(imidazol‐1‐ylmethyl)‐5‐methylbenzene) has been hydrothermally synthesized by the reaction of dimb with Co(NO₃)₂·6H₂O in aqueous solution. The cobalt(II) atoms are linked by bridging dimb ligands to form 2D corrugated and wavy networks containing Co₄(dimb)₄ macrocyclic motifs. Two neighboring independent layers interlinked each other in a parallel fashion to construct three‐dimensional structure by O–H···O, N–H···O and C–H···O hydrogen bonds. Magnetic measurement shows the weak antiferromagnetic interaction with a one‐dimensional chain model in the range of 5–300 K, with J of –0.68 cm⁻¹.     

New Hexachalcogeno–Hypodiphosphates of the Alkali Metals: Synthesis,Crystal Structure and Vibrational Spectra of the Hexathiodiphosphate(IV) Hydrates K4[P2S6] · 4 H2O,Rb4[P2S6] · 6 H2O,and Cs4[P2S6] · 6 H2O

The new hexathiodiphosphate(IV) hydrates K₄[P₂S₆] · 4 H₂O ( 1 ), Rb₄[P₂S₆] · 6 H₂O ( 2 ), and Cs₄[P₂S₆] · 6 H₂O ( 3 ) were synthesized by soft chemistry reactions from aqueous solutions of Na₄[P₂S₆] · 6 H₂O and the corresponding heavy alkali‐metal hydroxides. Their crystal structures were determined by single crystal X‐ray diffraction. K₄[P₂S₆] · 4 H₂O ( 1 ) crystallizes in the monoclinic space group P 2₁/n with a = 803.7(1), b = 1129.2(1), c = 896.6(1) pm, β = 94.09(1)°, Z = 2. Rb₄[P₂S₆] · 6 H₂O ( 2 ) crystallizes in the monoclinic space group P 2₁/c with a = 909.4(2), b = 1276.6(2), c = 914.9(2) pm, β = 114.34(2)°, Z = 2. Cs₄[P₂S₆] · 6 H₂O ( 3 ) crystallizes in the triclinic space group with a = 742.9(2), b = 929.8(2), c = 936.8(2) pm, α = 95.65(2), β = 112.87(2), γ = 112.77(2)°, Z = 1. The structures are built up by discrete [P₂S₆]^4? anions in staggered conformation, the corresponding alkali‐metal cations and water molecules. O ··· S and O ··· O hydrogen bonds between the [P₂S₆]^4? anions and the water molecules consolidate the structures into a three‐dimensional network. The different water‐content compositions result by the corresponding alkali‐metal coordination polyhedra and by the prefered number of water molecules in their coordination sphere, respectively. The FT‐Raman and FT‐IR/FIR spectra of the title compounds have been recorded and interpreted, especially with respect to the [P₂S₆]^4? group. The thermogravimetric analysis showed that K₄[P₂S₆] · 4 H₂O converted to K₄[P₂S₆] as it was heated at 100 °C.     

Zero Thermal Expansion in K0.46Co1.27[Fe(CN)6]·5.5H2O

Thermal expansion of materials is a comparatively easy‐understood physical property. Prussian blue analogues are of particular interest in engineering as new zero thermal expansion materials. We investigated the thermal expansion in K_0.46Co_1.27[Fe(CN)₆] · 5.5H₂O by x‐ray powder diffraction. This compound is a good example of a zero thermal expansion material. The origin of zero thermal expansion is considered to be the low frequency transverse vibrational motion of the cyano bridges.     

Solvothermal Synthesis and Crystal Structures of Two Thioantimonate(V) Compounds with the [SbS4]3— Anion Acting as a Monodentate Ligand: [Mn(C6H18N4)(C6H19N4)]SbS4 and [Mn(C6H14N2)3]2[Mn(C6H14N2)2(SbS4)2]·6H2O

The two novel thioantimonate(V) compounds [Mn(C₆H₁₈N₄)(C₆H₁₉N₄)]SbS₄ ( I ) and [Mn(C₆H₁₄N₂)₃][Mn(C₆H₁₄N₂)₂(SbS₄)₂]·6H₂O ( II ) were synthesized under solvothermal conditions by reacting elemental Mn, Sb and S in the stoichiometric ratio in 5 ml tris(2‐aminoethyl)amine (tren) at 140 °C or chxn (trans‐1, 2‐diaminocyclohexane, aqueous solution 50 %) at 130 °C. Compound I crystallises in the triclinic space group P1¯, a = 9.578(2), b = 11.541(2), c = 12.297(2)Å, α = 62.55(1), β = 85.75(1), γ = 89.44(1)°, V = 1202.6(4)ų, Z = 2, and II in the monoclinic space group C2/c, a = 32.611(2), b = 13.680(1), c = 19.997(1)Å, β = 117.237(5)°, V = 7931.7(8)ų, Z = 4. In I the Mn²⁺ cation is surrounded by one tetradentate tren molecule, one protonated tren acting as a monodentate ligand and a monodentate [SbS₄]^3— anion yielding a distorted octahedral environment. In II one unique Mn²⁺ ion is in an octahedral environment of three bidentate chxn molecules and the second independent Mn²⁺ ion is coordinated by two chxn ligands and two monodentate [SbS₄]^3— units leading to a distorted octahedral surrounding. The compounds were investigated and characterized with thermal and spectroscopic methods.     

M[B(CN)4]2: Zwei neue Tetracyanoborate mit zweiwertigen Kationen (M = Zn,Cu)

M[B(CN)₄]₂: Two new Tetracyanoborate Compounds with divalent Cations (M = Zn, Cu) The reaction of ZnO or CuO with [H₃O][B(CN)₄] in aqueous solution yielded single crystals of Zn[B(CN)₄]₂ and Cu[B(CN)₄]₂, respectively. The compounds were characterized by single‐crystal X‐ray diffraction. Zn[B(CN)₄]₂ ( (no. 164), a = b = 7.5092(9) Å, c = 6.0159(6) Å, Z = 1) crystallizes isotypic with Hg[B(CN)₄]₂. The structure of Cu[B(CN)₄]₂ (C2/m (no. 12), a = 13.185(3) Å, b = 7.2919(9) Å, c = 6.029(1) Å, β = 93.02(2)°, Z = 2) can be considered as a super‐structure, resulting from Jahn‐Teller distortion of the Cu²⁺ ions. Magnetic measurements were performed for the copper compound. Vibrational spectra and thermal stabilities were compared with the known mercury(II) tetracyanoborate.     

New Borate‐citrate: Synthesis,Structure, and Properties of Sr[B(C6H5O7)2](H2O)4·3H2O

Single crystals of Sr[B(C₆H₅O₇)₂](H₂O)₄ · 3H₂O, a new borate‐citrate material, were grown with sizes up to 8 × 6 × 2 mm by slow evaporation of water at room temperature. The structure of Sr[B(C₆H₅O₇)₂](H₂O)₄ · 3H₂O was determined by single‐crystal X‐ray diffraction. It crystallizes in the monoclinic space group P2₁/c, with a = 11.363(3) Å, b = 18.829(4) Å, c = 11.976(3) Å, β = 110.736(3)°, and Z = 4. The SrO₈ dodecahedra, BO₄ tetrahedra and citrate groups are linked together to form chains. The compound was characterized by IR and UV/Vis/NIR transmittance spectroscopy as well as thermal analysis.     

Tetracyanometallates with Complex Dien Cations: [Ni(dien)2][Ni(CN)4]·2H2O and [Ni(dien)2][Pd(CN)4]

The crystal structures of two square tetracyanocomplexes were determined. [Ni(dien)₂][Ni(CN)₄]·2H₂O (NDNCH) and [Ni‐(dien)₂][Pd(CN)₄] (NDPC) (dien = diethylene triamine) exhibit ionic structures consisting of mer‐[Ni(dien)₂]²⁺ cations and [Ni(CN)₄]^2‐ or [Pd(CN)₄]^2‐ anions, respectively. Moreover, the structure of NDNCH is completed by two water molecules of crystallisation. In both compounds hydrogen bonds contribute to the stabilisation of the structure. NDNCH dehydrates on air quickly yielding anhydrous [Ni(dien)₂][Ni(CN)₄] (NDNC). Its thermal decomposition proceeds in a complicated process followed by aerial oxidation of metallic nickel to NiO.     

A New Energetic Complex [Co(2,4,3‐tpt)2(H2O)2]·2NO3: Synthesis,Structure, and Catalytic Thermal Decomposition for Ammonium Perchlorate

The energetic complex, [Co(2,4,3‐tpt)₂(H₂O)₂] · 2NO₃ ( 1 ) [2,4,3‐tpt = 3‐(2‐pyridyl)‐ 4‐(4'‐pyridyl)‐5‐(3′‐pyridyl)‐1H‐1,2,4‐triazole], was synthesized and characterized by single‐crystal X‐ray diffraction, thermogravimetric analyses, elemental analysis, X‐ray powder diffraction, and IR spectroscopy. The title complex is a 0D motif with a unit of [Co(2,4,3‐tpt)₂(H₂O)₂]²⁺, whereas NO₃^– ions not only act as counter anions to balance the charge of the Co^II cations, but also provide hydrogen bond interactions, which make the 0D motif into a 1D chain. Furthermore, the thermal decomposition of ammonium perchlorate (AP) with complex 1 was explored by differential scanning calorimetry (DSC) over the temperature range from 50–500 °C. AP is completely decomposed in a shorter time in the presence of complex 1 , and the decomposition heat of the mixture is 2.143 kJ g^–1, significantly higher than pure AP. By Kissinger's method, the ratio of E_a/ln(A) is 11.87 for the mixture, which indicates that complex 1 shows good catalytic activity toward AP decomposition.     

Darstellung,spektroskopische Charakterisierung und Kristallstrukturen von Quecksilber(II)‐bis(tetracyanoborat) Hg[B(CN)4]2 und Diquecksilber(I)‐bis(tetracyanoborat) Hg2[B(CN)4]2

Preparation, Spectroscopic Characterization and Crystal Structures of Mercury(II)‐bis(tetracyanoborate) Hg[B(CN)₄]₂ and Dimercury(I)‐bis(tetracyanoborate) Hg₂[B(CN)₄]₂ Hg[B(CN)₄]₂ ( 1 ) is synthesised by the reaction between Hg(NO₃)₂ and K[B(CN)₄]₂. In a comproportionation reaction of 1 with elemental mercury the corresponding mercury(I) salt Hg₂[B(CN)₄]₂ ( 2 ) is obtained. The compounds were characterised by vibrational‐ and NMR‐spectroscopy, and their crystal structures were determined. Hg[B(CN)₄]₂ crystallizes in the trigonal system in the space group P3¯m1 with a = 781.75(3) pm, c = 601.68(2) pm, V = 318.44(2)ų, and one formula unit per unit cell. For Hg₂[B(CN)₄]₂ an orthorhombic unit cell with a = 568.9(1) pm, b = 3280.9(7) pm, c = 601.68(2) pm, V = 1389.6(5)Å, and Z = 4 is observed.     

Structural and Vibrational Studies of Sr2[W(CN)8]·10H2O

The crystal structure of distrontium octacyanotungstate decahydrate, Sr₂[W(CN)₈] · 10H₂O, was solved using X‐ray single crystal diffraction. The tungsten atom lies on a two fold axis. Eight cyanide anions create tetragonal antiprismatic coordination sphere of tungsten atom. The two edge‐sharing tetragonal antiprisms of [Sr(NC)₃(OH₂)₅], create a dimer, [Sr₂(CN)₆(H₂O)₆(μ‐H₂O)₂], which lies on the inversion center. One symmetry independent water molecule is located in a void of 40 Å³. Vibrational (FT‐IR and FT‐Raman spectroscopic) behavior of main structural units is discussed. It was spectroscopically confirmed that the geometry of [W(CN)₈]^4– anion is slightly distorted from that corresponding to “free” anion. The number of observed bands is significantly lower than that expected for C₂ point group.     

Crystal Structure of two Lanthanide(III) Glycolate Complexes, [Lu(HOCH2COO)2(H2O)4][Lu(HOCH2COO)4] and Dy2(OCH2COO)2(HOCH2COO)2 · 4H2O. An X‐Ray Diffraction and Vibrational Spectroscopic Study

The crystal structure of [Lu(HOCH₂COO)₂(H₂O)₄][Lu(HOCH₂COO)₄] ( 1 ) and Dy₂(OCH₂COO)₂(HOCH₂COO)₂ · 4H₂O ( 2) were determined by X‐ray crystallography. The space group of 1 and 2 are P2/c and P2₁/c, respectively. In 1 , discrete anions and cations held together by hydrogen bonds form the lattice, while the structure of 2 is a 3‐D network of cross‐linked metal‐ligand chains. The lanthanides are eight‐coordinated by chelating glycolate ligands and water molecules with distorted dodecahedral coordination. The core of 2 is a centrosymmetric dimer complex formed by two dysprosium atoms bridged by two oxygen atoms from deprotonated hydroxyl groups of glycolate ligands. The vibration spectra of the crystals were also measured and compared to each other.     

Co(en)3[B4O5(OH)4]Cl·3H2O和[Ni(en)3][B5O6(OH)4]2·2H2O的合成、结构以及热力学性质

利用水热法合成了两种过渡金属配合物为模板剂的含水硼酸盐晶体Co(en)3[B4O5(OH)4]Cl·3H2O(1) 和 [Ni(en)3][B5O6(OH)4]2·2H2O (2),并通过元素分析、X射线单晶衍射、红外光谱及热重分析对其进行了表征。化合物1晶体结构的主要特点是在所有组成Co(en)33+, [B4O5(OH)4]2–, Cl– 和 H2O之间通过O–H…O、O–H…Cl、N–H…Cl和N–H…O四种氢键连接形成网状超分子结构。化合物2晶体结构的特点是[B5O6(OH)4]–阴离子通过O–H…O氢键连接形成沿a方向有较大通道的三维超分子骨架,模板剂[Ni(en)3]2+阳离子和结晶水分子填充在通道中。     

Syntheses and Crystal Structures of the Cyclotriphosphate Hydrates Nd(P3O9)·3H2O,Nd(P3O9)·4.5H2O,RE(P3O9)·5H2O (RE = Pr,Nd), and Na3RE(P3O9)2·6H2O (RE = Pr,Nd)

Several rare‐earth cyclotriphosphate hydrates were obtained from mixtures of sodium cyclotriphosphates and the respective rare‐earth chlorides. Nd(P₃O₉) · 3H₂O [P$\bar{6}$ , Z = 3, a = 677.90(9), c = 608.67(9) pm, R₁ = 0.016, wR₂ = 0.038, 312 data, 36 parameters] was obtained by a solid state reaction and is isotypic with respective rare‐earth phosphate hydrates, while all the others adopt new structure types. Nd(P₃O₉) · 4.5H₂O [C2/c, Z = 8, a = 1644.6(3), b = 756.11(15), c = 1856.1(4) pm, β = 97.25(3)°, R₁ = 0.032, wR₂ = 0.081, 1763 data, 194 parameters], Nd(P₃O₉) · 5H₂O [P2₁/c, Z = 4, a = 773.75(15), b = 1149.1(2), c = 1394.9(3) pm, β = 106.07(3)°, R₁ = 0.042, wR₂ = 0.082, 1338 data, 194 parameters], Pr(P₃O₉) · 5H₂O [P$\bar{1}$ , Z = 2, a = 745.64(15), b = 889.07(18), c = 934.55(19) pm, α = 79.00(3), β = 80.25(3), γ = 66.48(3), R₁ = 0.059, wR2 = 0.089, 1468 data, 193 parameters], Na₃Nd(P₃O₉)₂ · 6H₂O [P2₁/n, Z = 4, a = 1059.78(18), b = 1207.25(15), c = 1645.7(4) pm, β = 99.742(17), R₁ = 0.047, wR₂ = 0.119, 1109 data, 351 parameters] and Na₃Pr(P₃O₉)₂ · 6H₂O [P2₁/n, Z = 4, a = 1061.42(16), b = 1209.0(2), c = 1635.5(3) pm, β = 99.841(13), R₁ = 0.035, wR₂ = 0.062, 1323 data, 350 parameters] were obtained by careful crystallization at room temperature. A thorough structure discussion is given. The infrared spectrum of Nd(P₃O₉) · 4.5H₂O is also reported.     

Synthesis,Crystal Structure and Characterization of a new Protonated Magnesium Borophosphate: (H3O)Mg(H2O)2[BP2O8]·H2O

A new protonated borophosphate (H₃O)Mg(H₂O)₂[BP₂O₈]·H₂O ( 1 ) was synthesized under mild hydrothermal conditions and characterized by single‐crystal X‐ray diffraction, FTIR spectroscopy and TG‐DTA. The compound crystallizes in the hexagonal system, space group P6(1)22 (No 178), a = 9.4462(7) Å, c = 15.759(2) Å, V = 1217.8(2) Å³, and Z = 6. There exist infinite helical $^1_\infty$ {[BP₂O₈]^3–} ribbons built up from corner‐sharing PO₄ and BO₄ tetrahedra, which are connected by MgO₄(H₂O)₂ leading to an infinite three‐dimensional open‐framework. The H₃O⁺ ions are located at the free thread of the helical ribbons, whereas crystallized water occupy the channels of the helical ribbons. The dehydration of the compound occurs at a higher temperature which is presumably due to the anisotropic hydrogen bonds in the crystal structure. The luminescent properties of the compound were studied.     

Über die Kristallstrukturen der Cyanokomplexe [Co(NH3)6][Fe(CN)6], [Co(NH3)6]2[Ni(CN)4]3 · 2 H2O und [Cu(en)2][Ni(CN)4]

On the Crystal Structures of the Cyano Complexes [Co(NH₃)₆][Fe(CN)₆], [Co(NH₃)₆]₂[Ni(CN)₄]₃ · 2 H₂O, and [Cu(en)₂][Ni(CN)₄] Of the three title compounds X‐ray structure determinations were performed with single crystals. [Co(NH₃)₆][Fe(CN)₆] (a = 1098.6(6), c = 1084.6(6) pm, R3, Z = 3) crystallizes with the CsCl‐like [Co(NH₃)₆][Co(CN)₆] type structure. [Co(NH₃)₆]₂[Ni(CN)₄]₃ · 2 H₂O (a = 805.7(5), b = 855.7(5), c = 1205.3(7) pm, α = 86.32(3), β = 100.13(3), γ = 90.54(3)°, P1, Z = 1) exhibits a related cation lattice, the one cavity of which is occupied by one anion and 2 H₂O, whereas the other contains two anions parallel to each other with distance Ni…Ni: 423,3 pm. For [Cu(en)₂][Ni(CN)₄] (a = 650.5(3), b = 729.0(3), c = 796.5(4) pm, α = 106.67(2), β = 91.46(3), γ = 106.96(2)°, P1, Z = 1) the results of a structure determination published earlier have been confirmed. The compound is weakly paramagnetic and obeys the Curie‐Weiss law in the range T < 100 K. The distances within the complex ions of the compounds investigated (Co–N: 195.7 and 196.4 pm, Ni–C: 186.4 and 186.9 pm, resp.) and their hydrogen bridge relations are discussed.