A Molecular Orbital Study of the Stereochemistry of Pentacoordinated Aluminium

1979 ◽  
Vol 32 (2) ◽  
pp. 231 ◽  
Author(s):  
RJ Hill ◽  
GV Gibbs ◽  
RC Peterson
Keyword(s):  
Total Energy ◽  
Molecular Orbital ◽  
Minimum Energy ◽  
Edge Length ◽  
Hydroxyl Groups ◽  
Bond Lengths ◽  
Pyramidal Geometry ◽  
Trigonal Bipyramidal ◽  
Square Pyramidal Geometry ◽  
Shared Edge

An attempt has been made to characterize the stereochemical requirements of an aluminium atom coordinated by five hydroxyl groups (AlO5H52-) within the framework of CNDO/2 molecular orbital formalism. Total energy surfaces calculated for this system as the valence angles are varied within the constraints of C2v symmetry clearly show the 'reaction coordinate' for the so-called Berry pseudo- rotation mechanism. With all Al-O and O-H bond lengths fixed at 1.84 and 1.00 Ǻ respectively, the activation energy for trigonal-bipyramidal/square-pyramidal interconversion is 7.1 kJ mol-1. In addition, the minimum energy O(axial)-Al-O(basal) angle for the square-pyramidal group is estimated to be c. 103.5°. When one bond is lengthened relative to the other four the trigonal-bipyramidal configuration is further stabilized, but approaches tetrahedral geometry. When one bond is shortened square-pyramidal geometry is stabilized and the minimum energy O(ax)-Al-O(bs) angle increases. With two bonds lengthened (or shortened) the favoured trigonal-bipyramidal configuration is the one with long bonds directed towards the axial positions and at no stage is there a stabilization of square-pyramidal geometry. These results agree with trends in calculated Mulliken bond overlap populations and with observed ratios of axial-to-basal bond lengths in suggesting that for trigonal- bipyramidal stereochemistry the axial bonds are weaker, whereas for square-pyramidal geometry the axial bond is stronger. Moreover, consideration of the total energy for various isomers of Al(OH)4F2- indicates that more electronegative substituents prefer to enter the apical and basal positions in a trigonal bipyramid and a square pyramld respectively. For a cluster Al2(OH)82-, consisting of two aluminium trigonal-bipyramidal groups sharing a common edge of variable length, an energy minimum (62.2 kJ mol-1 lower than the undistorted case) is found at a shared edge length of 2.246 A, 13 % shorter than for the undistorted polyhedron. The corresponding observed distance for a similar dimer in the mineral andalusite, Al2SiO5, is 2.247(7) Ǻ. Plots of minimum energy shared edge length against mean bond length for various clusters M2(OH)8n-, where M = Al or Mg, clearly demonstrate an essentially linear relationship between the two parameters consistent wlth trends observed for natural systems in which M = Co, Cu, Mn and Zn.

Synthesis and crystal structure analyses of tri-substituted guanidine-based copper(II) complexes

2021 ◽  
Vol 76 (3-4) ◽  
pp. 193-199
Author(s):  
Muhammad Said ◽  
Sadia Rehman ◽  
Muhammad Ikram ◽  
Hizbullah Khan ◽  
Carola Schulzke
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Molecular Structures ◽  
Hydroxyl Groups ◽  
Synthesis And Crystal Structure ◽  
Pyramidal Geometry ◽  
Tautomeric Forms ◽  
Square Planar ◽  
Nitrogen Donor ◽  
Square Pyramidal Geometry

Abstract Three guanidine-derived tri-substituted ligands viz. N-pivaloyl-N′,N″-bis-(2-methoxyphenyl)guanidine (L1), N-pivaloyl-N′-(2-methoxyphenyl)-N″-phenylguanidine (L2) and N-pivaloyl-N′-(2-methoxyphenyl)-N″-(2-tolyl)guanidine (L3) were reacted with Cu(II) acetate to produce the corresponding complexes. The significance of the substituent on N″ for the resulting molecular structures and their packing in the solid state has been studied with respect to the structural specifics of the corresponding Cu(II) complexes. The key characteristic of the guanidine-based metal complexation with Cu(II) is the formation of an essentially square planar core with an N2O2 donor set. As an exception, in the complex of L1, the substituent’s methoxy moiety also interacts with the Cu(II) center to generate a square-pyramidal geometry. The hydroxyl groups of the imidic acid tautomeric forms of L1–L3, in addition to N″, are also bonded to Cu(II) in all three complexes rather than the nitrogen donor of the guanidine motif.

Different ZnIIcation coordination geometries in di-μ-acetato-bis{2-chloro-6-[(pyridine-2-ylmethylimino)methyl]phenol}dizinc(II) chloroform monosolvate

2013 ◽  
Vol 69 (11) ◽  
pp. 1348-1350 ◽  
Author(s):  
Young-Inn Kim ◽  
Jin Young Lee ◽  
Young-Kwang Song ◽  
Sung Kwon Kang
Keyword(s):  
Quantum Yield ◽  
Title Compound ◽  
The Other ◽  
Bidentate Coordination ◽  
Strong Emission ◽  
Pyramidal Geometry ◽  
Trigonal Bipyramidal ◽  
Coordinate Geometry ◽  
Square Pyramidal Geometry ◽  
Distorted Trigonal Bipyramidal

In the title compound, di-μ-acetato-κ2O:O;κ2O:O′-bis[(6-chloro-2-{(E)-[(pyridin-2-yl)methylimino]methyl}phenolato-κ3N,N′,O)zinc(II)], [Zn2(C13H10ClN2O)2(C2H3O2)2]·CHCl3, the ZnIIcation adopts a five-coordinate geometry and is coordinated by two N atoms and one O atom of a tridentate 6-chloro-2-{(E)-[(pyridin-2-yl)methylimino]methyl}phenolate ligand and two O atoms of two bridging acetate groups, but their coordination geometries differ. One ZnIIcation adopts a distorted trigonal bipyramidal geometry and the other a square-pyramidal geometry. The two acetate ligands bridge two ZnIIcations with mono- and bidentate coordination modes. The title compound exhibits a strong emission at 460 nm upon excitation at 325 nm with a quantum yield of 23.1%.

Dependence of the Distortion of the Square Pyramids in N, N-Dimethylethylenediammonium Pentachloroantimonate(III) on the Geometry of Hydrogen Bonds

2001 ◽  
Vol 56 (6) ◽  
pp. 521-525 ◽  
Author(s):  
Maciej Bujak ◽  
Jacek Zaleski
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Intermolecular Interactions ◽  
Mean Value ◽  
The Other ◽  
Monoclinic System ◽  
Bond Lengths ◽  
Pyramidal Geometry ◽  
The Mean ◽  
Square Pyramidal Geometry

AbstractN ,N-Dimethylethylenediammonium pentachloroantimonate(III) crystallizes in the monoclinic system, in space group P21/c (a = 12.460(2), b = 10.252(2), c = 10.330(2) Å, β = 97.75(3)°, V = 1307.5(4) Å3, Z = 4, dc = 1.997, dm = 1.99(2) g/cm3). The crystal structure of [(CH3)2NH(CH2)2NH3][SbCl5] consists of isolated [SbCl5]2- anions and [(CH3)2NH(CH2)2NH3]2+ cations. The [SbCl5]2- anion has a distorted square pyramidal geometry, presenting one short axial and four long equatorial Sb-Cl bonds. The square pyramids are characteristically stacked one close to the other, parallel to the c axis. The voids between the anionic sublattice are filled by [(CH3)2NH(CH2)2NH3]2+ cations. The five non-equivalent Sb-Cl bond distances within the [SbCl5]2- square pyramid are significantly different. The equatorial Sb-Cl bonds are in the range 2.427(2)-2.968(2) Å, whereas the axial one is 2.384(1) Å long. The study reveals that N-H...C1 hydrogen bonds are responsible for the deformation of equatorial Sb-Cl bonds from the mean value of 2.654(7) Å. Analysis of intermolecular interactions between the [SbCl5]2- pyramids in the structure, reflected in changes of Sb-Cl bond lengths from the values characteristic of non-interacting pyramids, leads to the conclusion that the van der Waals radius of Sb is significantly smaller than that estimated by Pauling.

scholarly journals Crystal structure of di-μ-hydroxido-bis{aqua[ethyl (1,10-phenanthrolin-3-yl)phosphonato-κ2N,N′]copper(II)} heptahydrate

2018 ◽  
Vol 74 (12) ◽  
pp. 1751-1754
Author(s):  
Alexander Yu. Mitrofanov ◽  
Yoann Rousselin
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Water Molecule ◽  
Title Compound ◽  
Binuclear Complex ◽  
Three Dimensional ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Pyramidal Geometry ◽  
Square Pyramidal Geometry

In the title compound, [Cu2(OH)2{C12H7N2(PO3C2H5)}2(H2O)2]·7H2O, two Cu2+cations are bridged by two hydroxide groups, forming a centrosymmetric binuclear complex. Each Cu2+cation is further coordinated by the N atoms of a bidentate ethyl (1,10-phenanthrolin-3-yl)phosphonate anion and a water molecule in a square-pyramidal geometry. In the crystal, a network of O—H...O hydrogen bonds involving the P(O)(O−)(OEt) groups, bridging hydroxyl groups, coordinated and uncoordinated water molecules generates a three-dimensional supramolecular structure. The ethyl group exhibits disorder and was modelled over three sites with occupancies of 0.455, 0.384 and 0.161.

scholarly journals Bis{μ4-N-[phenyl(pyridin-2-ylazanidyl)methyl]pyridin-2-aminido}tetrakis(tetrahydrofuran)tetralithium

2013 ◽  
Vol 69 (12) ◽  
pp. m683-m683 ◽  
Author(s):  
Juan Chen
Keyword(s):  
Complex Molecule ◽  
Title Complex ◽  
Coordination Modes ◽  
Bond Lengths ◽  
Pyramidal Geometry ◽  
Metal Atoms ◽  
Square Pyramidal Geometry

The title complex, [Li4(C17H14N4)2(C4H8O)4], bears a novel tetradentate diamido ligand. In the tetranuclear centrosymmetric complex molecule, the metal atoms exhibit two kinds of coordination modes. The middle two Li+cations are coordinated by four N (ligand) and one O (tetrahydrofuran, THF) atoms, resulting in a distorted square-pyramidal geometry. The outer two Li+cations are in distorted tetrahedral environments consisting of three N (ligand) and one O (THF) atoms. The Li—N bond lengths vary from 2.020 (7) to 2.441 (6)Å.

A CNDO/2 Molecular Orbital Study of Shared Tetrahedral Edge Conformations in Olivine-Type Compounds

1979 ◽  
Vol 32 (5) ◽  
pp. 949 ◽  
Author(s):  
TJ McLarnan ◽  
RJ Hill ◽  
GV Gibbs
Keyword(s):  
Detailed Analysis ◽  
Molecular Orbital ◽  
Minimum Energy ◽  
Orbital Energy ◽  
Molecular Orbital Calculations ◽  
Molecular Orbital Study ◽  
The Individual ◽  
Olivine Structure ◽  
Semi Empirical ◽  
Shared Edge

Semi-empirical molecular orbital calculations have been used to study the shortening of tetrahedral shared edges in olivine-type compounds. The shared edge conformation in forsterite was modelled by a cluster of SiO3(OH)Mg3(OH)107- composition, consisting of a silicate tetrahedron sharing edges with three magnesium-containing octahedra. Predicted tetrahedron edge lengths agree well with observed values. Calculations on similar clusters representing shared edge conformations in sinhalite, chrysoberyl, and γ-Na2BeF4 also predict shortening of shared edges with d(X2-X3) < d(X3-X3), (X = O,F), as observed. Calculations on Mg2SiS4 fail to predict shortened shared edges. Detailed analysis of the individual molecular orbital energy terms indicates that the minimum energy configuration is determined by a complex sum of one- and two-centre energies. Distortions due to dimensional misfit of polyhedra in olivine structure space group P bnm appear to have relatively little importance in shortening the shared edges of the tetrahedron.

scholarly journals Tetrakis[μ3-2-(piperidin-1-yl)ethanolato]tetrakis[chloridocopper(II)]

2014 ◽  
Vol 70 (5) ◽  
pp. m194-m194
Author(s):  
Mei Luo ◽  
Yong-Hua Huang ◽  
Jing-Cheng Zhang
Keyword(s):  
Intermolecular Interactions ◽  
Minor Component ◽  
Chair Conformation ◽  
Hydroxyl Groups ◽  
Tetranuclear Complex ◽  
Pyramidal Geometry ◽  
A Minor ◽  
Square Pyramidal Geometry

In the title tetranuclear compound, [Cu4(C7H14NO)4Cl4], each CuIIcation isN,O-chelated by a piperidineethanolate anion and coordinated by a Cl−anion and two O atoms from neighboring piperidineethanolate anions in a distorted NO3Cl square-pyramidal geometry. The deprotonated hydroxyl groups of the piperidineethanolate anions bridge CuIIcations, forming the tetranuclear complex. All piperidine rings display a chair conformation. In the crystal, there are no significant intermolecular interactions present. The crystal studied was an inversion twin refined with a minor component of 0.18 (5).

Synthesis, Characterization and Crystal Structures of Monomeric and Imidazolate-Bridged Polymeric Copper(II) Complexes of 5-Methyl-1,5,9-triazanonane

2000 ◽  
Vol 53 (10) ◽  
pp. 883 ◽  
Author(s):  
Hai-Liang Zhu ◽  
Xiao-Lan Yu ◽  
Xiao-Ming Chen
Keyword(s):  
Oxygen Atom ◽  
Variable Temperature ◽  
Magnetic Measurement ◽  
Orthorhombic Space Group ◽  
Apical Position ◽  
Space Group ◽  
Pyramidal Geometry ◽  
Trigonal Bipyramidal ◽  
Square Pyramidal Geometry ◽  
Distorted Trigonal Bipyramidal

Two complexes [Cu(mtan)(H2O)(ClO4)](ClO4) (Im = imidazolate) (1) and [Cu(mtan)(Im)]n (ClO4)2n (mtan = 5-methyl-1,5,9-triazanonane) (2) have been prepared and characterized. Single-crystal X-ray analysis reveals that (1) crystallizes in the orthorhombic space group Pbcm, with a 8.906(5), b 12.255(6), c 14.821(4) Å and V 1618(1) Å3, and complex (2) crystallizes in the orthorhombic space group Pca21, with a 11.125(7), b 9.149(6), c 15.180(7) Å and 1545(1) Å3. The copper(II) atom in complex (1) is in a distorted square-pyramidal geometry, being coordinated by three nitrogen atoms from an mtan ligand and one oxygen atom from an aqua ligand at the basal plane and one perchlorate oxygen atom at the apical position. The structure of complex (2) features polymeric cationic chains composed of [Cu(mtan)(Im)]+ repeating units and discrete perchlorate anions. The Cu(1) atom in each unit has a severely distorted trigonal-bipyramidal geometry, being coordinated by three nitrogen atoms from one mtan ligand and two nitrogen atoms from two Im groups. The structural units are linked by -Im groups to give one-dimensional chains. The variable-temperature magnetic measurement on the powder sample of (2) reveals intrachain, medium antiferromagnetic interaction with g = 2.240 and J = –36.45 cm–1 through the -Im bridges.

scholarly journals Crystal structure of {(R)-N2-[(benzo[h]quinolin-2-yl)methyl]-N2′-[(benzo[h]quinolin-2-yl)methylidene]-1,1′-binaphthyl-2,2′-diamine-κ4N,N′,N′′,N′′′}(trifluoromethanesulfonato-κO)zinc(II)} trifluoromethanesulfonate dichloromethane 1.5-solvate

2017 ◽  
Vol 73 (7) ◽  
pp. 949-953
Author(s):  
Shayna R. Skokan ◽  
Monica M. Reeson ◽  
Kayode D. Oshin ◽  
Anastasiya I. Vinokur ◽  
John A. Desper ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Metal Atom ◽  
Title Compound ◽  
Asymmetric Unit ◽  
Torsion Angles ◽  
Positional Disorder ◽  
Bond Lengths ◽  
Pyramidal Geometry ◽  
Imine Bond ◽  
Square Pyramidal Geometry

The zinc(II) atom in the title compound, [Zn(C48H31N4)(CF3SO3)](CF3SO3)·1.5CH2Cl2, adopts a distorted five-coordinate square-pyramidal geometry. It is coordinated by one trifluoromethanesulfonate ligand and four N atoms of theN2-[(benzo[h]quinolin-2-yl)methyl]-N2′-[(benzo[h]quinolin-2-yl)methylidene]-1,1′-binaphthyl-2,2′-diamine ligand. The complex is present as a single-strandedP-helimer monohelical structure incorporating π–π and/or σ–π interactions. One of the imine bonds present in the original ligand framework is reduced, leading to variations in bond lengths and torsion angles for each side of the ligand motif. The imine-bond reduction also affects the bond lengths involving the metal atom with the N-donor atoms located on the imine bond. There are two molecules of the complex in the asymmetric unit. One of the molecules exhibits positional disorder within the coordinating trifluoromethanesulfonate ion making the molecules symmetrically non-equivalent.

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