Mercury(II) Compounds with 1,3-Benzothiazole-2-thione. Spectral, Thermal, and Crystal Structure Studies

Mercury(II) halides, HgX₂ (X = Cl^–, Br^–, I^–) react with 1,3-benzothiazole-2-thione (btztH) in methanol solutions giving the HgX₂(btztH) and HgX₂(btztH)₂ types of compounds. Mercury(II) acetate gives the thiolato compound Hg(btzt)₂ because of the deprotonation of btztH. Hg(btzt)₂ reacts with 2,2-bipyridine (bipy) giving a 1:1 complex. IR, ¹H, and ¹³C NMR spectral studies indicate that btztH acts as a monodenatate ligand through the S thione donor atom in all complexes. The X-ray crystal structure determinations of [HgI₂(btztH)]₂, HgBr₂(btztH)₂, Hg(btzt)₂, and Hg(btzt)₂(bipy) have been carried out revealing tetrahedrally coordinated mercury atom in [HgI₂(btztH)]₂ and HgBr₂(btztH)₂, while in Hg(btzt)₂(bipy) 2 + 2 coordination is achieved through strong Hg (N(bipy) contacts. A linear coordination in Hg(btzt)₂ is not affected by the Hg N contacts, which are longer than in Hg(btzt)₂(bipy), but still shorter than the van der Waals sum of mercury and nitrogen covalent radii. [HgI₂(btztH)]₂ exists as centrosymmetrical dimer with a Hg₂I₂ bridging core. The dimeric molecules are linked by the intermolecular hydrogen bonds between the terminal iodine atom and the NH group [3.63(1) Å] into infinite chains along the z-axis. There are N–H Br(bridging) intermolecular hydrogen bonds in HgBr₂(btztH)₂ joining molecules into endless chains along the x-axis. The Br(bridging) atom acts as double proton acceptor and two NH groups as proton donors [NH Br(bridging) 3.278(9) and 3.338(7) Å]. The mercury to sulfur and mercury to halogen bond distances in [HgI₂(btztH)]₂ and HgBr₂(btztH)₂ are discussed in relation to the analogous compounds, revealing strong influence of hydrogen bonds on their relative strengths as well as crystal packing requirements of the ligand. The sulfur and halogen atoms are more tightly bound to mercury implicating severe distortion of the coordination polyhedron in the structures in which they do not take part in hydrogen bonds formation. The influence of steric requirements of the ligands in Hg(btzt)₂ and Hg(btzt)₂(bipy) on the distortion of the mercury coordination polyhedra accompanied with the relative strength of Hg N contacts is considered.     

Two-Dimensional Supramolecular from the Self-Assembly of Dissymmetrical Oxamidato-Bridged Heterometallic Trinuclear Building Blocks: Synthesis, Crystal Structure, and Magnetic Properties

Two heterometallic trinuclear complexes {[Cu(oxbp)]₂Co(H₂O)₂}1.5DMF0.5H₂O (complex 1) and {[Cu(oxbm)]₂Co(H₂O)₂}2DMF (complex 2) were obtained from the self-organization of two new dissymmetrical oxamidato-bridged copper(II) building blocks [Cu(oxbp)]^– and [Cu(oxbm)]^–[H₃oxbp=N-benzoato-N'-(3-aminopropyl)oxamido, H₃oxbm=N-benzoato-N'-(2-amino-2-methylethyl)oxamido, DMF=dimethylformamide]. The crystal structure of complex 1 has been determined. Complex 1 crystallize in triclinic system, space group P-1, a=8.0609(16) Å, b=10.661(2) Å, c=22.279(5) Å, =85.32(3), =86.64(3), =70.90(3), and Z=1. The crystal structure of complex 1 consists of neutral trinuclear complex units, and hydrogen bond involved DMF and water molecules. Through the hydrogen bonds, weak coordination and CuCu weak interactions, complex 1 features a 2-D supramolecular structure. Magnetic susceptibility measurements (5–100 K) indicate that the central Co(II) and terminal copper metal ions are antiferromagnetically coupled with J=–28.09 and J=–29.70 cm^–1 for complex 1 and 2, respectively.     

Reaction of H2PtCl6 with 18-crown-6 and dibenzo-18-crown-6 in 1,2-dichloroethane and acetonitrile

Compounds of the compositions [2(18-crown-6)6(H₂O)2(C₂H₄Cl₂){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], [4(18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)(Pt₂Cl₁₀)^2–], [(dibenzo-18-crown-6)6(H₂O){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], and [4(dibenzo-18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)Pt₂Cl₁₀)^2–] were prepared by reactions of H₂PtCl₆ with 18-crown-6 and dibenzo-18-crown-6.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1593–1599.Original Russian Text Copyright © 2004 by Guseva, Busygina, Khasanshin, Polovnyak, Yarkova, Yusupov.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis and X-Ray Crystal Structure Study of ]2-Methyl-4-(2-methylbenzoyl)-phenoxy] Acetic Acid Hydrazide

Benzophenone analog 3 has been synthesized and characterized by the X-ray diffraction (XRD) method. The compound crystallizes in a monoclinic space group P2₁/c with cell parameters a = 7.701(8) Å, b = 7.151(5) Å, c= 28.323(3) Å, = 104.639(4)°, Z = 4. The structure exhibits intra- and intermolecular hydrogen bonding of the type N–HO, C–HO, and N–HN. The molecules are interlinked through hydrogen bonds forming an infinite chain. This polymeric-like structure may play an important role in biological activity.     

An Inorganic-Organic Hybrid Supramolecular Hydrogen-Bonding and π-π Stacking Network Containing Ge4S4− 10 Cluster: Synthesis and Characterization of (H2bipy)2Ge4S10⋅(bipy)⋅7H2O (bipy=4,4′-bipy)

The reactions of TMA₄Ge₄S₁₀ (TMA=tetramethylammonium), Cu(NO₃)₂3H₂Oand 4,4-bipy under hydrothermal environment result in the formation of (H₂bipy)₂Ge₄S₁₀(bipy)7H₂O (1), which has been structurally characterized by single crystal X-ray analysis. The 3-D structure of 1 can be viewed as an inorganic-organic hybrid supramolecular hydrogen-bonding (hydrogen bonds: O–HO, N–HN, C–HO, N–HO, and O–HS) and - stacking network containing Ge₄S^4– ₁₀ clusters and novel [H₂bipybipyH₂bipy] trimers.     

Gold(I) Formamidinate Clusters: The Structure, Luminescence, and Electrochemistry of the Tetranuclear, Base-Free [Au4(ArNC(H)NAr)4]

The structures of the tetragold(I) formamidinate cluster complexes, [Au₄(ArNC(H)NAr)₄], Ar=C₆H₄-4-OMe (1), C₆H₃-3,5-Cl (2), C₆H₄-4-Me (3), have been characterized by x-ray crystallography. The range of AuAu distances is 2.8–3.0 Å. The angles at AuAuAu are acute and obtuse 70 and 109°, 88 and 91°, and 63 and 116° in 1, 2, and 3, respectively. The four gold atoms are located at the corner of a rhomboid with the formamidinate ligands bridged above and below the near plane of the four Au(I) atoms. The tetranuclear gold(I) complexes show a bright blue-green luminescence under UV light, with an emission at 490 nm and a weak emission at 530 nm in the solid state, at room temp and 77 K. The oxidation of the formamidinate cluster, 1, has been studied electrochemically in 0.1 M Bu₄NPF₆/CH₂Cl₂ at a Pt working electrode with different scan rates. Three waves were obtained, 0.75, 0.95, and 1.09V vs. Ag/AgCl at a scan rate of 500 mV/s, the three waves are reversible. The potentials are independent of the scan rate in the range 50 mV/s to 3 V/s. The current at the third wave is larger than those at the first two.     

STRUCTURAL STUDIES OF POLYETHER COORDINATION TO MERCURY(II) HALIDES: CROWN ETHER VERSUS POLYETHYLENE GLYCOL COMPLEXATION

Abstract

The crystal structures of several crown ether and polyethylene glycol complexes of HgX₂ (X=Cl, Br, I) have been investigated. The crown ether complexes studied are [HgX₂(18-crown-6)] (X=Br, I) and [HgI₂(dibenzo-18-crown-6)]·CH₃CN. In each case Hg resides in the cavity of the ether resulting in hexagonal bipyramidal geometry with axial, terminal halides. The covalently bonded halides reside closer to Hg than the oxygen donor atoms. Five polyethylene glycol complexes have been structurally characterized: [(HgCl₂)₃(EO3)], [HgX₂(EO4)] (X=Br, I), [HgCl₂(EO5)], and [HgBr₂(EO5)HgBr₂]₂ (EO3=triethylene glycol, EO4=tetraethylene glycol, EO5=pentaethylene glycol). The EO4 and EO5 glycols mimic crown ethers by forming an equatorial girdle around Hg although in each case one alcoholic terminal end does not coordinate to the metal ion. Each complex also has two covalent, nearly linear, axial halides coordinated to Hg. In [(HgCl₂)₃(EO3)], the glycol is linear and coordinates to three Hg atoms all on the same side of the glycol ligand. This structure is polymeric via chloride bridging.     

Study of acid-base interactions of mono- and diazaporphyrin indium complexes with acetic and trifluoroacetic acids by <Superscript>1</Superscript>H NMR and electronic spectroscopy

Indium complex of 13,17-dibutyl-2,3,7,8,12,18-hexamethyl-5-azaporphyrin (Cl)InMAP was synthesized, and acid-base interactions of the meso-nitrogen atoms in (Cl)InMAP and its diaza analog (Cl)InDAP with acetic and trifluoroacetic acids were studied by ¹H NMR and electronic spectroscopy. Depending on the medium, the complexes and proton-donor species HA give rise to acid solvates >N(HA)_n which are converted to final acid-base interaction products, H-complexes >NH+A^–(HA)_m or ionic associates >NH⁺A^–(HA)_l , as the acidity of the medium rises. In acetic acid solution, the acid solvates derived from more basic (Cl)InMAP exist in equilibrium with the H-associates (pK _a1 = 4.45±0.03). From (Cl)InDAP, the corresponding H-associates are formed only in the presence of H₂SO₄ (pK _a1 = 2.10±0.03). In more polar media (solutions of trifluoroacetic acid in methylene chloride), ionic associates are formed, which involve one [(Cl)InMAP, pK ₁ = 2.46±0.02] or two meso-nitrogen atoms [(Cl)InDAP, pK ₁ = 2.11±0.03, pK ₂ = 0.41±0.04).Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1546–1556.Original Russian Text Copyright © 2004 by Stuzhin, Ivanova, Migalova.This revised version was published online in April 2005 with a corrected cover date.     

The Molecular Structure and NMR Properties of P-Phosphinoylmethyl Aminophosphonium Salts

The molecular structures of two aminophosphonium salts (bromide and tetrafluoroborate) have been determined by X-ray analysis. They have similar conformations and hydrogen bond (HB) networks: the N–H acid proton is bonded to the anion and, in the case of the fluoroborate, to the oxygen atom of the phosphine oxide, forming a pseudo six-membered ring closed by a weak N–HO intramolecular hydrogen bond (IMHB). These compounds have been studied by multinuclear NMR in solution, including the ¹⁵N-labeled derivatives, to determine a complete set of coupling constants. A coupling of 1.5 Hz between the ¹⁵N and the ³¹P nuclei, separated by three bonds, was observed experimentally for the bromide in CDCl₃ solution, which appears to be a classical ³ J _N-P across the covalent bonds and not a ^3h J _N-P across the IMHB.     

Gold(I) Pyrazolate Clusters: The Structure and Luminescence of the Tetranuclear, Base-Stabilized [(dppm)2Au4(3,5-Ph2Pz)2](NO3)2 ⋅ H2O

The tetranuclear Au(I) pyrazolate complex, [(dppm)₂Au₄(3,5-Ph₂Pz)₂](NO₃)₂  H₂O, 1, has been synthesized and structurally characterized. It is the first tetranuclear pyrazolate of Au(I) to have been found, although the trinuclear pyrazolates of Au(I) are well known. Complex 1 exhibits luminescence at 77 K when excited at 333 nm with an emission maximum at 454 nm. The emission has been assigned to ligand to metal charge transfer, LMCT, based upon the vibronic structure that is observed. The complex crystallizes in the monoclinic space group P2₁/c, with a=19.33(3) Å, b=20.26(3) Å, c=19.80(3) Å, =106.74(2)°, V=7425(17) ų, Z=8, and R=0.058. The Au    Au distances are Au(1)    Au(4)=3.185(3) Å, Au(1)    Au(2)=3.230(3) Å, Au(2)    Au(3)=3.079(3) Å, and Au(3)    Au(4)=3.280(3) Å.     

Synthesis, Structural Characterization, and Magnetic Properties of a New Charge-Transfer Salt Composed of Polyoxotungstate Acceptors [WVWVI 5O19]3− and Cationic Ferrocenyl CpFe+Cp Donors

The crystal structure of the charge-transfer slat (CpFe⁺Cp)₃[W^VW^VI ₅O₁₉] (CpFeCp=Fe(C₅H₅)₂), synthesized from the reaction of Na₂WO₄2H₂O with ferrocene under acid conditions, has been determined by single-crystal X-ray diffraction. The crystal is of triclinic space group P(–1) with a=13.0374(3), b=15.0406(3), c=16.8239(1) Å, =91.417(1), =98.931(1), =115.294(1)°, V=2931.20(9) ų, Z=1, M _r =5895.57, F(000)=2652, =18.735 mm^–1, and D _c =3.340 gcm^–3. The final R factor is 0.0502 for 10173 (R _int=0.0563) unique reflections and 770 parameters. The structural analysis reveals that there are two crystallographically distinct [W^VW^VI ₅O₁₉]^3– polyoxoanions and six independent ferrocene cations per unit cell. Each polyoxoanion consists of six WO₆ octahedra with three types of W–O bond lengths. Interestingly, CpFe⁺Cp moieties are stacked to form octagonal channels that incorporate the polyanions. The closest FeFe distances between the neighboring ferrocenyl cations are more than 6.49 Å, therefore, a good magnetic isolation between the iron centers is expected.     

On the crystal chemistry of three copper(II)-arsenates: Cu3(AsO4)2-III,Na4Cu(AsO4)2, and KCu4(AsO4)3

The three copper(II)-arsenates were synthesized under hydrothermal conditions; their crystal structures were determined by single-crystal X-ray diffraction methods:Cu₃(AsO₄)₂-III:a=5.046(2) Å,b=5.417(2) Å,c=6.354(2) Å, =70.61(2)°, =86.52(2)°, =68.43(2)°,Z=1, space group ,R=0.035 for 1674 reflections with sin / 0.90 Å^–1.Na₄Cu(AsO₄)₂:a=4.882(2) Å,b=5.870(2) Å,c=6.958(3) Å, =98.51(2)°, =90.76(2)°, =105.97(2)°,Z=1, space group ,R=0.028 for 2157 reflections with sin / 0.90 Å^–1.KCu₄(AsO₄)₃:a=12.234(5) Å,b=12.438(5) Å,c=7.307(3) Å, =118.17(2)°,Z=4, space group C2/c,R=0.029 for 1896 reflections with sin / 0.80 Å^–1.Within these three compounds the Cu atoms are square planar [4], tetragonal pyramidal [4+1], and tetragonal bipyramidal [4+2] coordinated by O atoms; an exception is the Cu(2)^[4+1] atom in Cu₃(AsO₄)₂-III: the coordination polyhedron is a representative for the transition from a tetragonal pyramid towards a trigonal bipyramid. In KCu₄(AsO₄)₃ the Cu(1)^[4]O₄ square and the As(1)O₄ tetrahedron share a common O—O edge of 2.428(5) Å, resulting in distortions of both the CuO₄ square and the AsO₄ tetrahedron. The two Na atoms in Na₄Cu(AsO₄)₂ are [6] coordinated, the K atom in KCu₄(AsO₄)₃ is [8] coordinated by O atoms.Die drei Kupfer(II)-Arsenate wurden unter Hydrothermalbedingungen gezüchtet und ihre Kristallstrukturen mittels Einkristall-Röntgenbeugungsmethoden ermittelt:Cu₃(AsO₄)₂-III:a = 5.046(2) Å,b = 5.417(2) Å,c = 6.354(2) Å, = 70.61 (2)°, = 86.52(2)°, = 68.43(2)°,Z = 1, Raumgruppe ,R = 0.035 für 1674 Reflexe mit sin / 0.90 Å^–1.Na₄Cu(AsO₄)₂:a = 4.882(2) Å,b = 5.870(2) Å,c = 6.958(3) Å, = 98.51(2)°, = 90.76(2)°, = 105.97(2)°,Z = 1, Raumgruppe ,R = 0.028 für 2157 Reflexe mit sin / 0.90 Å^–1.KCu₄(AsO₄)₃:a = 12.234(5) Å,b = 12.438(5) Å,c = 7.307(3) Å, = 118.17(2)°,Z = 4, Raumgruppe C2/c,R = 0.029 für 1896 Reflexe mit sin / 0.80 Å^–1.Die Cu-Atome in diesen drei Verbindungen sind durch O-Atome quadratisch planar [4], tetragonal pyramidal [4 + 1] und tetragonal dipyramidal [4 + 2]-koordiniert; eine Ausnahme ist das Cu(2)^{[4 + 1]}-Atom in Cu₃(AsO₄)₂-III: Das Koordinationspolyeder stellt einen Vertreter des Übergangs von einer tetragonalen Pyramide zu einer trigonalen Dipyramide dar. In KCu₄(AsO₄)₃ haben das Cu(1)^[4]O₄-Quadrat und das As(1)O₄-Tetraeder eine gemeinsame O—O-Kante von 2.428(5) Å, was eine Verzerrung der beiden Koordinationsfiguren CuO₄-Quadrat und AsO₄-Tetraeder bedingt. Die zwei Na-Atome in Na₄Cu(AsO₄)₃ sind durch O-Atome [6]-koordiniert, das K-Atom in KCu₄(AsO₄)₃ ist [8]-koordiniert.

---

Zur Kristallchemie dreier Kupfer (II)-Arsenate: Cu₃(AsO₄)₂-III, Na₄Cu(AsO₄)₂ und KCu₄(AsO₄)₃

     

Mechanisms of Heterogeneous Processes in the System SiO2 + CH4: III. Products of >Si

Permenov  D. G.  Radzig  V. A. 《Kinetics and Catalysis》2004,45(2):273-278

Chiral coordination polymers based on Re cluster complexes,Cu<Superscript>2+</Superscript> cations,and 1,2<Emphasis Type="Italic">S</Emphasis>,3<Emphasis Type="Italic">S</Emphasis>,4-tetraaminobutane

Reactions of octahedral and tetrahedral chalcocyanide cluster complexes of Re with Cu²⁺ cations and 1,2S,3S,4-tetraaminobutane (Threo-tab) were used to synthesize and study the structures of the following six novel chiral complexes: [{Cu₂(NH₃)(Threo-tab)₃}Re₆S₈(CN)₆] 3H₂O (I) (where Threo is 1,2S,3S,4-tetraaminobutane), [{Cu₂(NH₃)(Threo-tab)₃}Re₆Se₈(CN)₆] 2H₂O (II), [{Cu(Threo-tab)}₂Re₆Te₈(CN)₆] 13.5H₂O (III), [{Cu(Threo-tab)}₂Re₄Te₄(CN)₁₂] 6.5H₂O (IV), [{Cu₂(NH₃)(Threo-tab)₂}Re₄Te₄(CN)₁₂] 4H₂O (V), and [{Cu(NH₃)(Threo-tab)}]₂[Re₄S_3.4Te_0.6(CN)₁₂] 1.25H₂O (VI). The structures of complexes I–IV contain extended channels of sufficiently large size capable of including guest molecules.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 289–301.Original Russian Text Copyright © 2005 by Mironov, Naumov, Brylev, Efremova, Fedorov, Hegetschweiler.     

2,6-Dioxa-3,7-dioxotricyclo[3.3.3.01,5]undecane, a Propellanoid Dilactone Representing a New Tricyclic Ring System

The title material, tetrahydro-3a,6a-propanofuro-[3,2-b]furan-2,5-dione (C₉H₁₀O₄), is a new compound representing a previously unreported ring system. Its asymmetric unit lacks an axis of symmetry because of nonplanarity in the carbon ring. Although the bulk material is racemic, only single enantiomers are incorporated into the crystal, which is unusually dense. Several intermolecular C–H O close contacts were found.     

Thermal,FTIR and XRD study on some 1:1 molecular compounds of theophylline

Thermal stability and structural features of three newly synthesized 1:1 lattice compounds of theophylline (th) with ethylenediamine carbamate (enCO₂), 1,10-phenanthroline (phen), and 5-sulfosalicylic acid (sa-5-SO₃H) have been studied in comparison with those of the theophylline compounds with ethanolamine (ea) and salicylic acid (sa). Simultaneous TG-DTA measurements, FTIR spectroscopy and X-ray diffraction have been carried out to get information on the various structural units of these solid inclusions, especially on the actual form (molecule, anion or cation) of theophylline moieties built in. Theophyllinate and theophyllinium ions have been found in the ethanolammonium-theophyllinate (1:1) (1, eaH⁺th^-) and the theophyllinium salicylic acid 5-sulfonate monohydrate (1:1:1), (5, thH⁺saSO_–³H₂O), respectively. Whilst the 1:1 complexes with 1,10-phenanthroline (2, thphen), ethylenediamine carbamate (3, thenCO₂), and salicylic acid (4, thsa) contain neutral theophylline moieties associated with H-bonds. In compound (3) the zwitterion of N-(2-ammonium-ethyl)carbamate (NH₃⁺-CH₂-CH₂-NH-CO_-²) is present.This revised version was published online in November 2005 with corrections to the Cover Date.     

Crystal Structure of [Co?6H2O][Co?4H2O?2Gly]?2SO4

The crystals of [Co6H₂O][Co4H₂O2Gly]2SO₄ were studied by X-ray diffraction analysis (triclinic, P , a = 5.975(5), b = 15.469(5), c = 6.765(5) , =120.71(5), =83.23(5), =98.77(5)°). The structure contains complex cations of two types: [Co6H₂O]²⁺ and [Co4H₂O2Gly]²⁺ and SO ₄ ^2– anions linked by hydrogen bonds and electrostatic forces. Three chemically nonequivalent charged layers can be distinguished in the structure: one layer is formed by cobalt hexaaqua complexes, another by [Co4H₂O2Gly]^2– complexes, and the third layer consists of sulfate anions interlaying the former two. The layers alternate along the b axis and are connected by a 3D system of hydrogen bonds.     

Products and kinetics of the thermal decomposition of (l-(−)-menthyl)[2,2′-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphite ozonide

Two conformers (chair, boat) of [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphite ozonide have been obtained by the low temperature ozonization (–80 °C) of [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphite. It was determined that decomposition of the ozonide is first order with the rate constant logk ₀ = (10.92±1.10)–(14.02±1.25)/gq ( = 2.303RT, kcal mol^–1), leading to [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphate and oxygen (including singlet oxygen). Conformational transitions (chair-boat) for [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphate have been registered by³¹P NMR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1758–1761, October, 1994.This work was supported by Russian Foundation for Basic Research (Project No. 93-03-532l).     

Nickel complexes of 1-methylimidazoline-2(3H)-thione: crystal structures of trans-dichlorotetrakis(1-methylimidazoline-2(3H)-thione)nickel(II) and tetrakis[1-methylimidazoline-2(3H)-thione]nickel(II) tetrafluoroborate

Summary Crystal structures have been determined for two nickel complexes of the monodentate S-donating ligand 1-methyl imidazoline-2(3H)-thione (mimtH). The parainagnetic trans-octahedral complex, [Ni(mimtH)₄Cl₂], crystallises in an orthorhombic unit cell (a=12.459(1),b=13.078(1),c=15.406(1)Å, V=2510.24ų,Z=4, space group Pbca). Final conventional R from 1848 observed data [F>4(F)] is 0.0273. The Ni–Cl distance is. 2.537(1) Å and the mean Ni–S distance is 2.479 Å.The diamagnetic complex, [Ni(mimtH)₄](BF₄)₂, contains a distorted square-planar cation which is H-bonded. to [BF₄]^– anions. The complex crystallises in an orthorhombic unit cell [a=9.810(1),b=14.585(1),c=20.120(2)Å, V=2878.8ų,Z=4, space group Pbcn]. Final conventional R from 1756 observed data [F>4(F)] is 0.0629. The average Ni–S distance is 2.216Å.     

Molecular Structure of Silicon Tetraiodide

The molecular geometry of silicon tetraiodide was determined by gas-phase electron diffraction at 378 K. The molecule has a regular tetrahedral shape with an Si—I bond length (r _g) of 2.432(5) Å and an II nonbonded distance (r _g) of 3.971(8) Å. There is an apparent anharmonicity in both the stretching and the bending vibrations, with the latter especially pronounced.