Showing papers on "Tetrahedral molecular geometry published in 1993"
TL;DR: In this article, the crystal structures of fructose-1,6-bisphosphatase (EC 3.11) complexed with substrate alone or with substrate analogues in the presence of divalent metal ions have been determined.
Abstract: The crystal structures of fructose-1,6-bisphosphatase (EC 3.1.3.11) complexed with substrate alone or with substrate analogues in the presence of divalent metal ions have been determined. The substrate analogues, 2,5-anhydro-D-glucitol-1,6-bisphosphate (AhG-1,6-P2) and 2,5-anhydro-D-mannitol-1,6-bisphosphate (AhM-1,6-P2), differ from the alpha and beta anomers of fructose-1,6-bisphosphate (Fru-1,6-P2), respectively, in that the OH on C2 is replaced by a hydrogen atom. Structures have been refined at resolutions of 2.5 to 3.0 A to R factors of 0.172 to 0.195 with root-mean-square deviations of 0.012-0.018 A and 2.7-3.8 degrees from the ideal geometries of bond lengths and bond angles, respectively. In addition, the complex of substrate with the enzyme has been determined in the absence of metal. The electron density at 2.5-A resolution does not distinguish between alpha and beta anomers, which differ for the most part only in the position of the 1-phosphate group and the orientation of the C2-hydroxyl group. The positions of the 6-phosphate and the sugar ring of the substrate analogues are almost identical to those of the respective anomer of the substrate. In the presence of metal ions the positions of the 1-phosphate groups of both alpha and beta analogues differ significantly (0.8-1.0 A) from those of anomers of the substrate in the metal-free complex. Two metal ions (Mn2+ or Zn2+) are located at the enzyme active site of complexes of the alpha analogue AhG-1,6-P2. Metal site 1 is coordinated by the carboxylate groups of Glu-97, Asp-118, and Glu-280 and the 1-phosphate group of substrate analogue, while the metal site 2 is coordinated by the carboxylate groups of Glu-97, Asp-118, the 1-phosphate group of substrate analogue, and the carbonyl oxygen of Leu-120. Both metal sites have a distorted tetrahedral geometry. However, only one metal ion (Mg2+ or Mn2+) is found very near the metal site 1 in the enzyme's active site in complexes of the beta analogue AhM-1,6-P2 or for Mg2+ in the complex of the alpha analogue AhG-1,6-P2. This single metal ion is coordinated by the carboxylate groups of Glu-97, Asp-118, Asp-121, and Glu-280 and the 1-phosphate group of substrate analogue in a distorted square pyramidal geometry.(ABSTRACT TRUNCATED AT 400 WORDS)
85 citations
TL;DR: In this article, a series of 14-20 membered tetraamide macrocyclic complexes, [ML n ] 2+, where M = Ni II and Cu II, or a tetrahedral geometry for M = Co II and Zn II have been assigned.
67 citations
TL;DR: In this paper, the crystal structure of [Cu(PPh3)2(pymtH)I] has been determined by single-crystal X-ray diffraction methods.
48 citations
TL;DR: A family of rigid tetrahedral molecules based on tetraphenylmethane has been synthesized as discussed by the authors, which are used for molecular engineering of architecturally regular macromolecular systems.
Abstract: A family of rigid tetrahedral molecules based on tetraphenylmethane has been synthesized. The primary preparative chemistry involved Suzuki coupling. Reactions typically proceeded in good yields providing synthetic entry to tetrahedral building blocks for molecular engineering of architecturally regular macromolecular systems.
40 citations
TL;DR: In this article, the geometries and energy separations of several electronic states of Yn (n=2-4) were computed using the complete active space self-consistent field (CASSCF) followed by multireference singles+doubles configuration interaction (MRSDCI).
Abstract: We compute the geometries and energy separations of several electronic states of Yn (n=2–4). The complete‐active‐space self‐consistent‐field (CASSCF) followed by multireference singles+doubles configuration interaction (MRSDCI) calculations which included up to 2.6 million configurations are made in this study. We find two nearly degenerate states, namely, 3T1 and 1A1 of tetrahedral geometry, as candidates for the ground state of Y4. The Y–Y bond lengths are computed as 3.41 and 3.42 A for 3T1 and 1A1 states, respectively. The electronic states with the rhombus structures are found to be ≥0.34 eV above the tetrahedral ground state for Y4. We found two nearly degenerate electronic states with D3h geometries as candidates for the ground state of Y3 (2A‘2 and 2A’1). Two electronic states of Y2, namely, 5Σu− and 1Σg+ (short R) are also studied.
36 citations
TL;DR: In this article, a series of complexes with the tridentate dibasic Schiff base ligand o-vanillin isonicotinoyl hydrazone (o-VINH) were prepared and characterized by i.a.p. and electronic spectral studies, magnetic susceptibility measurements and t.m.
Abstract: A new series of complexes with the tridentate dibasic Schiff base ligand o-vanillin isonicotinoyl hydrazone (o-VINH) were prepared and characterized by i.r., 1H n.m.r. and electronic spectral studies, magnetic susceptibility measurements and t.g.a. The disappearance of low field signals due to OH, NH protons at 10.23 and 9.31 p.p.m. and downfield shift of the −CH=N proton signal at 8.17 p.p.m. in the n.m.r. spectrum confirms the involvement of these groups in coordination. Both t.g.a. and i.r. spectral data show evidence for one molecule of coordinated H2O. These results taken in conjunction with electronic spectral data allow assignation of tetrahedral geometry for manganese(II), nickel(II) and palladium(II) complexes but a square planar configuration to cobalt(II), copper(II) amd zinc(II) complexes.
28 citations
TL;DR: In this paper, the first two members of a homologous series of model alkane-like molecules which incorporate the identities of the backbone and substituent atoms as hard-sphere sites are examined.
Abstract: The equation of state of the first two members of a homologous series of model alkane-like molecules which incorporate the identities of the backbone and substituent atoms as hard-sphere sites is examined. These polyatomic molecules are formed from tangentially bonded hard spheres with diameters σ1 and σ2, where spheres of type 1 make up the backbone of the chain, and spheres of type 2 represent the substituent atoms. The spheres are bonded together in a tetrahedral geometry so that all of the bond angles are ω = 109°; for the second and higher homologues dihedral angles χ about the 1–1 bonds also have to be specified. In order to test the predictions of a recent bonded hard-sphere (BHS) theory, isothermal-isobaric Monte Carlo (MC-NPT) simulations are undertaken for methane- and ethane-like molecules with different diameter ratios σ2/σ1 over a range of densities in the fluid state. In the case of the ethane-like molecules trans (χ = 30°) and freely rotating geometries are examined. The simulation data are...
28 citations
TL;DR: In this article, the spectral invariants gamma1 and alpha1, proportional to the zeroth and first spectral moments, due to bimolecular collisions between CH4 and N2 were obtained from these data and compared with theoretical values.
Abstract: The far infrared absorption of a CH4-N2 mixture was measured at 297, 195, and 162 K from 30 to 650/cm. The spectral invariants gamma1 and alpha1, proportional, respectively, to the zeroth and first spectral moments, due to bimolecular collisions between CH4 and N2 were obtained from these data and compared with theoretical values. The theory for collision-induced dipoles between a tetrahedral and a diatomic or symmetrical linear molecule includes contributions not previously considered. Whereas the theoretical values of gamma1 are only somewhat greater than experiment at all temperatures, the theoretical values of alpha1 are significantly lower than the experimental values. From the theoretical spectral moments for the various induced dipole components, the parameters of the BC shape were computed, and theoretical spectra were constructed. Good agreement was obtained at the lower frequencies, but with increasing frequencies the theoretical spectra were increasingly less intense than the experimental spectra. Although the accuracy of the theoretical results may suffer from the lack of a reliable potential function, it does not appear that this high frequency discrepancy can be removed by any conceivable modification in the potential.
24 citations
TL;DR: In this article, the synthesis and single-crystal structure of Li8(HPO4)(BePO4)6·H2O (BePO-LOS), which is a topological equivalent of the synthetic low-sodium aluminosilicate zeolite losod, Na6(AlSiO4), 6·9 H2O, was reported.
19 citations
TL;DR: In this paper, the Coriolis coupling strength in stretching vibrational states of XH 4 species is investigated as a function of the extent of bond localisation by use of the Darling-Dennison resonance formalism of Mills and Robiette.
17 citations
TL;DR: In this article, the formation constants, enthalpies and entropies of four mononuclear complexes [MIICln](2−n)+(n= 1−4) have been determined for M = Mn and Co at 298 K and for Mn = Mn at 318 K.
Abstract: The formation of chloro complexes of manganese(II) and cobalt(II) has been studied in N,N-dimethylacetamide (DMA) by calorimetry and spectrophotometry. Formation constants, enthalpies and entropies of four mononuclear complexes [MIICln](2–n)+(n= 1–4) have been determined for M = Mn and Co at 298 K and for M = Mn at 318 K. In spite of the similar solvent properties of DMA and N,N-dimethylformamide (DMF), overall formation of [MCl4]2– is strongly favoured and less endothermic in DMA than in DMF. Electronic spectra of the CoII complexes obtained at 278, 298 and 318 K indicate an octahedral geometry for [Co(DMA)6]2+ and tetrahedral geometries for [CoCl(DMA)3]+, [CoCl2(DMA)2], [CoCl3(DMA)]– and [CoCl4]2– at each temperature, though an additional solvation equilibrium is observed for the monochloro complex: [CoCl(DMA)5]+⇌[CoCl(DMA)3]++ 2DMA. The relatively large values of ΔH°1 and ΔS°1 suggest that extensive desolvation occurs on formation of the monochloro complex. Thus, the coordination geometry primarily alters at an earlier step (n= 1) in DMA than in DMA (n= 2). For the MnII system, large ΔH°n and ΔS°n values (n= 1, 2) are also diagnostic of an earlier transition from octahedral to tetrahedral geometry in DMA. The results show that the stability and structure of the complexes are strongly controlled by sterically hindered solvation of DMA molecules towards the metal ion, leading to the more favourable, less endothermic complexation and the tendency to form a less-crowded solvation structure. The steric effect of DMA is more pronounced in the order MnII < CoII < NiII.
TL;DR: In this article, the title compounds were synthesized from [Ge(OH) 2 - {RN(CH 2 CH 2 O) 2 }] (R=H or CH 3 ) and the corresponding ligands in refluxed methanol.
TL;DR: The crystal structure of triamterinium tetrachlorocuprate (II), (C12H13N7)CuCl4, was determined by X-ray diffraction as discussed by the authors.
TL;DR: The title alkene as discussed by the authors, which is calculated to have an approximately tetrahedral geometry at each doubly bonded carbons, has been generated by dehalogenation of 3,7-diiodotricyclo[3.3.1] nonane in the gas phase, using both potassium and cesium vapor, and has been isolated in an argon matrix at 10 K.
Abstract: The title alkene, which is calculated to have an approximately tetrahedral geometry at each of the doubly bonded carbons, has been generated by dehalogenation of 3,7-diiodotricyclo[3.3.1.O 3,7 ]nonane in the gas phase, using both potassium and cesium vapor, and has been isolated in an argon matrix at 10 K. The IR bands belonging to the alkene have been identified by photobleaching the matrix-isolated material and recording the difference spectrum. A weak band at 1496 cm -1 in the IR spectrum is assigned to the double-bond stretch on the basis of both semiempirical and ab initio electronic structure calculations
TL;DR: The bis-benzene cluster [Os6H2(CO)11(η6-C6H6)(µ3-η2:η 2: η2-C 6H6)]3 in this paper showed that the six osmium atoms adopt a bicapped tetrahedral geometry with one benzene ligand in a terminal η6 site and the other in a face-capping µ3-∆ 2.
Abstract: Treatment of [Os5H4(CO)11(η6-C6H6)]1 with 1,8-diazabicyclo[5.4.0]undec-7-ene in CH2Cl2 gives the dianion [Os5H2(CO)11(η6-C6H6)]2–2, and subsequent reaction of 2 with [Os(η6-C6H6)(MeCN)3][BF4]2 provides the new bis-benzene cluster [Os6H2(CO)11(η6-C6H6)(µ3-η2:η2:η2-C6H6)]3 in ca. 35% yield, the X-ray analysis of which shows that the six osmium atoms adopt a bicapped tetrahedral geometry with one benzene ligand in a terminal η6 site and the other in a face-capping µ3-η2:η2:η2 site.
TL;DR: The crystal structures of the compounds [M(NMTP)] 4 (BF 4 ) 2 (M=Zn 2+, Ni 2+ ; NMTP=N-methyl-2-thioxopyrrolidine) are reported in this article.
Abstract: The crystal structures of the compounds [M(NMTP)] 4 (BF 4 ) 2 (M=Zn 2+ , Ni 2+ ; NMTP=N-methyl-2-thioxopyrrolidine) are reported. Whereas the zinc(II) complex has a nearly regular tetrahedral geometry, the nickel(II) complex is significantly distorted in the manner predicted by the Jahn-Teller theorem, with trans-SNiS angles decreasing from the tetrahedral value of 109.5 to 85 o . Metal-ligand bonding parameters have been derived from an analysis of the optical spectrum of [Ni(NMTP)] 4 (BF 4 ) 2
TL;DR: In this article, a solid hetero-bimetallic complex of Ba+2 and Cu+2 was prepared by slow evaporation of a 3/1 CH3CN/CH3OH mixture containing 15-crown-5 and the chloride salts of Ba, Cu, and Y+3.
Abstract: A solid hetero-bimetallic complex of Ba+2 and Cu+2 was prepared by slow evaporation of a 3/1 CH3CN/CH3OH mixture containing 15-crown-5 and the chloride salts of Ba+2, Cu+2, and Y+3. The resulting complex was studied using single crystal X-ray diffraction. [Ba(15-crown-5)2][CuCl4] crystallizes in the monoclinic space group Pn with cell parameters (20°C), a=12.119(2), b=9.386(2), c=13.475(3)A, β=93.81(2)°, and D calc=1.70 g cm−3 for Z=2. Ba+2 is coordinated to all 10 oxygen atoms of two 15-crown-5 molecules in a sandwich geometry. Cu+2 is coordinated to the four chloride anions and exhibits a distorted tetrahedral geometry. The two shortest Cu…Ba separations are 6.855(2) and 6.902(2)A.
TL;DR: In this article, the magnetic susceptibility of the title compound has been measured in the range 74-300 K and shows linear Curie-Weiss behaviour with C - 14.3, θ = 1.2 K and μeff = 10.77 B.
TL;DR: In this article, a large number of triorganodiiododophophosphorus compounds with unactivated cobalt metal in dry diethyl ether have been studied, and the reactions produce the novel ionic complexes [PR3I][Co(PR3)I3] in quantitative yield.
Abstract: The reactions of a large number of triorganodiiododophosphorus compounds, R3Pl2[R3= Et3, Prn3, Bun3, PhMe2, Ph2Me, Ph2Prn, Ph3(o-,m-or p-MeC6H4)Ph2, or (m-MeC6H4)3], with unactivated cobalt metal in dry diethyl ether have been studied. All reactions produce the novel ionic complexes [PR3I][Co(PR3)I3] in quantitative yield, illustrated crystallographically for [PPh3I][Co(PPh3)I3]. However, where R3= PhMe2 both the ionic complex and the cobalt(III) complex [Co(PPhMe2)2I3] are produced from the same reaction. The previously reported isolation of the ‘frozen transition-state complex’[Co(PBun3)3I8] from the reaction of Bun3Pl2 with cobalt powder has been reinvestigated; when allowed to proceed to completion, the reaction produces the ionic complex described above. The compound Ph3PlBr reacts with cobalt powder to produce the mixed-halide ionic complex [PR3I][Co(PR3)IBr2]. All the complexes [PR3I][Co(PR3)I3] have been studied using Raman and visible spectroscopy, the latter confirming the tetrahedral geometry of the cobalt anion. Very little reaction is observed with the corresponding dibromophosphorus compounds, R3PBr2, but in some cases visible spectroscopic studies on the trace of complex formed suggest a tetrahedral cobalt(II) species, perhaps similar to the iodo-complexes described above. Additionally, Ph3SbI2 reacts with cobalt metal in an analogous way to Ph3Pl2 to produce the novel complex [SbPh3I][Co(SbPh3)I3].
TL;DR: The nuclear quadrupole interaction (NQI) of 111Cd substituted for Cu(II) on type-1 sites in blue copper proteins is characterized by high values of ω0 in the region of 300 Mrad/s, close to that for the catalytic zinc site in alcohol dehydrogenase as mentioned in this paper.
Abstract: The nuclear quadrupole interaction (NQI) of111Cd substituted for Cu(II) on type-1 sites in blue copper proteins is characterized by high values of ω0 in the region of 300 Mrad/s, close to that for the catalytic zinc site in alcohol dehydrogenase. Type-1 Cu has usually two sulfur ligands and two nitrogen ligands and in some cases an oxygen ligand in either a distorted tetrahedral geometry or in a trigonal bipyramidal geometry. The near tetrahedral arrangement together with the ligand sphere containing the same number of sulfur ligands explains the value of ω0 in the blue copper proteins. The present work determined the partial NQI for methionine using the known structure of azurin. This value was then used in the angular overlap model to calculate the NQI for ascorbate oxidase the structure of which is also known and gave good agreement with experiment. NQI data for laccase and stellacyanin the structures of which are unknown, are also given.
TL;DR: Binuclear complexes of manganese, cobalt, nickel, copper, and zinc with kanamycin sulphate have been synthesized and characterized by elemental analysis, IR, 1 H NMR, electronic and ESR spectra in order to throw more light on their structures.
TL;DR: In this paper, a completely protected L-histidyl(NτBzl)-containing peptides were synthesized and characterized by NMR spectroscopy, and the resulting peptide derivatives appear to be good ligands for CoII, ZnII and CuI.
Abstract: Five small, completely protected, L-histidyl(NτBzl)-containing peptides, were synthesized and characterized by NMR spectroscopy, i.e., R-Ala-His(Nτ-Bzl)-Ala-R′ (1), R-His(Nτ-Bzl)-Ala-Ala-Ala-Met-R′ (2), R-His(Nτ-Bzl)-Ala-Ala-Ala-His(Nτ-Bzl)-R′ (3), R-His(Nτ-Bzl)-Ala-His(Nτ-Bzl)-Ala-His(Nτ-Bzl)-R′ (4), R-His(Nτ-Bzl)-Ala-His(Nτ-Bzl)-R′ (5), in which: R is phenylacetyl (PhCH2CO-), R′ is phenylamino (-NHPh); Bzl is benzyl (PhCH2-).
It has been shown that benzylation of histidine residues takes place at the Nτ atom of the imidazole. The resulting peptide derivatives appear to be good ligands for CoII, ZnII and CuI. Titrations of zinc chloride solutions towards peptide solutions (in dmso-d6, dimethyl sulfoxide followed by NMR spectroscopy show the formation of the two species [Zn(NπHis)2Cl2] and [Zn(NπHis)(dmso)Cl2]. Copper(I)-chloride titrations result in formation of trigonal planar and tetrahedral complexes (in dmso-d6). Zinc, copper and cobalt trifluoromethanesulfonates were also investigated, and corresponding tetrahedral species with additional dmso ligands replacing chloride were obtained. In addition, octahedral complexes have been found, as shown for cobalt(II) using ligand-field spectroscopy.
Conductivity experiments of zinc chloride complexes in dmso and chloroform indicate non-electrolytes. Their very low conductivity in methanol indicates only slight dissociation of chloride, in agreement with a tetrahedral geometry for zinc(II). For [Co(NπHis)2Cl2], the UV-VIS adsorption spectra in dmso and in the solid state (diffuse reflection) are comparable, indicating tetrahedral geometry, with a CoN2Cl2 chromophore.
TL;DR: In this article, arylazopyrazolones derived from isoniazid and substituted phenylazoethyl-acetoacetates and two Co(II) complexes with N1-isonicoti-noyl-3-methy1-4-phenylazopyramolone have been synthe-sised.
Abstract: Complexes of Cu(II) with five arylazopyrazolones derived from isoniazid and substituted phenylazoethyl-acetoacetates and two Co(II) complexes with N1-isonicoti-noyl-3-methy1- 4-phenylazopyrazolone have been synthe-sised. The arylazopyrazolones act as neutral bidentate ligands, bonding to the metal through the azo nitrogen and hydroxyl oxygen. The complexes are non-electrolytes in DMSO and acetoni trile, showing that the anions are coordinated to the metal. Analytical, magnetic and electronic spectral data indicate an octahedral geometry for the chloro complexes and tetrahedral geometry for the bromo complexes of Cu(II). The Co(II) complexes are tetrahedral irrespective of the nature of the anion.
TL;DR: In this paper, N-(2-Pyridyl)acetamide was covalently immobilized onto silica gel giving 1.57 × 10-4 mol of this molecule per gram of silica.
Abstract: N-(2-Pyridyl)acetamide was covalently immobilized onto silica gel giving 1.57 × 10–4 mol of this molecule per gram of silica. This new bidentate chelate extracts MCl2(M = Ni, Co, Cu) from ethanol and acetone solutions. The photoacoustic spectra of the solid complexed samples were obtained in the visible and near-infrared spectral regions and were analysed using ligand field theory. The calculated Racah parameters indicate a tetrahedral geometry for nickel and cobalt and a highly distorted octahedral geometry for the copper complex.
TL;DR: In this article, an 18-electron rule was proposed for Fe2(μ-TePh)2(NO)4 on the basis of the 18 electron rule to obtain a Fe-Fe bond of length 2.827.
Abstract: Addition of NOBF4 to fac-[PPN][Fe(CO)3(TePh)3] in THF at ambient temperature results in formation of Fe2(μ-TePh)2(NO)4l Fe2(−TePh)2(CO)6 and organic products. Methylation of fac-[PPN][Fe(CO)3- (TePh)3] by Mel or [Me3O][BF4] leads to the known dimer Fe2(μ.-TePh)2(CO)6 and organic products. Fe2(μ-TePh)2(NO)4 crystallizes in the orthorhombic space group P bca, with a = 12.701(5) A, b = 6.7935(16) A, c = 21.299(9) A, V = 1837.8(11) A3, and Z = 4. The core geometry of Fe2(μ-TePh)2(NO)4 is best described as a Fe2Te2 planar rhombus with Te-Fe-Te bond angle 112.09(4)°. A Fe-Fe bond (length 2.827(2) A) is proposed for Fe2(μ-TePh)2(NO)4 on the basis of the 18-electron rule. The iron atom adopts a distorted tetrahedral geometry with acute bridge Fe-Te-Fe angles 67.91(3)°, and bridging Fe-Te bond of length 2.53(1) A.
TL;DR: The cationic complex is five coordinated and shows a distorted geometry intermediate between a square-based pyramid and a trigonal bipyramid as mentioned in this paper, but not all the Zn-N distances are equivalent.
Abstract: The cationic complex is five coordinated and shows a distorted geometry intermediate between a square-based pyramid and a trigonal bipyramid. Not all the Zn-N distances are equivalent. The ZnCl 4 2- anion shows a tetrahedral geometry
TL;DR: The X-ray crystal structure of Ph3Al·N(H2)t-Bu, I, has been determined in this paper, which represents the first structural characterization of a triarylaluminum-primary amine monomer.
Abstract: The X-ray crystal structure of Ph3Al·N(H2)t-Bu, I, has been determined. The title compound was prepared in high yield from reaction of Ph3Al with H2N(t-Bu) in hexane. Refinement of 813 observed reflections converged at R = 0.086. The Al-N bond distance is determined to be 1.98 (2)A while the aluminium atom has a distorted tetrahedral geometry. Compound I represents the first structural characterization of a triarylaluminum-primary amine monomer. Moreover, the title compound exhibits unusual thermal stability.
TL;DR: In this paper, the rotational dynamics of a single deuterated methane molecule in the presence of its twelve nearest neighbours has been studied by using a computer simulation technique, and the three-dimensional motion of the tetrahedral molecule is described by the appropriate algorithm equations, as well as by the well known Lennard-Jones potential.
Abstract: The rotational dynamics of a single deuterated methane molecule in the presence of its twelve nearest neighbours has been studied by using a computer simulation technique. The three-dimensional motion of the tetrahedral molecule is described by the appropriate algorithm equations, as well as by the well known Lennard-Jones potential. The importance of the inverse-twelfth-power repulsive potential for the dynamics of the deuterated methane molecule is also highlighted. The second-nearest neighbour interactions contribute only 7% to the potential energy of the whole system and this hardly affects the dynamics of the central molecule. A detailed analysis of the direction cosine data reveals a change in the dynamical behaviour of the molecule around the transition temperature, which could be attributed to the singularity observed in the specific heat data. Corresponding to the Lennard-Jones potential, the period of oscillation of the central molecule comes out to be 0·38xlO-12 s. Making use of the (dimensionless) average rotational kinetic energy at the transition, (ERK)critical = 6·3, and the period, the transition temperature is found to be 27·7 K, which is in quite good agreement with one of the ..\-type transition temperatures reported by Clusius et al.
TL;DR: The CaO8 complex was found to be dimensionally similar to corresponding complexes in other simple tetrahydrated calcium salts and to conform to rigid-body behavior while the CaO7 complex did not.
Abstract: The structure of the title compound consists of columns of Ca ions surrounded by four columns of perbromate ions and four columns of water molecules alternating in pairs. The CaO8 complex was found to be dimensionally similar to corresponding complexes in other simple tetrahydrated calcium salts. The eight coordinating O atoms form a polyhedron which departs only slightly from a (distorted) square antiprism. Each of the crystallographically inequivalent perbromate ions was found to conform to rigid-body behavior while the CaO8 complex did not. Although the perbromate ions depart moderately from regular tetrahedral geometry, the mean Br--O bond length agrees well with previously determined values. Hydrogen bonds in this structure involve water-oxygen acceptors as well as perbromate-oxygen acceptors.
TL;DR: The structure of methyltris(2,4,6-trimethoxyphenyl)phosphonium iodide, [CH 3 TMPP]I, shows slightly-distorted tetrahedral geometry at phosphorus as mentioned in this paper.
Abstract: The structure of methyltris(2,4,6-trimethoxyphenyl)phosphonium iodide, [CH 3 TMPP]I, shows slightly-distorted tetrahedral geometry at phosphorus. There are no close anion-cation contacts