Molecular geometry of coordinating

Hargittai, M., Hargittai, I. The molecular geometries of coordination compounds in the vapor phase. Budapest Akad6miai Kiado Amsterdam Elsevier 1977... 

M. Hargittai and 1. Hargittai, Molecular Geometries of Coordination Compounds in the Vapor Phase , Elsevier,... 

Hargittai, M. and Hargittai, I. (1977) The Molecular Geometries of Coordination Compounds in the Vapour Phase. Elsevier, Amsterdam and Akademiai Kiado, Budapest. 

The molecular geometry of a complex depends on the coordination number, which is the number of ligand atoms bonded to the metal. The most common coordination number is 6, and almost all metal complexes with coordination number 6 adopt octahedral geometry. This preferred geometry can be traced to the valence shell electron pair repulsion (VSEPR) model Introduced In Chapter 9. The ligands space themselves around the metal as far apart as possible, to minimize electron-electron repulsion. 

It is especially important to investigate the molecular structure of coordination compounds in the vapor phase because the relatively weak coordination interactions may be considerably influenced by intermolecular interactions in solutions and especially in crystals. It has been shown that the geometrical variations can be correlated with other properties of the molecular complexes ). In particular the structural changes in the F3B N(CH3)3 and CI3B N(CH3)3 molecules ) relative to the respective monomeric species unambiguously indicated boron trichloride to be a stronger acceptor than boron trifluoride. Data on the geometry and force field have also been correlated ). 

Z Matrix. A set of internal coordinates (bond lengths, bond angles and dihedral angles only) describing molecular geometry. Of historical interest only. 

FIGURE 53. Molecular geometry of five-coordinate organomagnesium complexes 108 and 109 in the solid state... 

FIGURE 42. Molecular geometry of 75 in the sohd state. Note that the CH2 groups of the coordinated THE molecules are omitted for clarity... 

The molecular geometry of phospholipid membranes is thus structurally analogous to inorganic phosphate minerals in that corrugated layers of metal ion-phosphate coordination complexes exist in membranes and minerals. In Fig. 5, the structure of a typical phosphate mineral is shown to reveal the type of molecular pattern that is exposed at the ionic surface of phospholipid membranes64,6S. For a recent review on membrane structure see66. ... 

The molecular geometry of Sr(OC6H2-f-Bu3)2(THF)3 can best be described as distorted trigonal bipyramidal. The large aryl oxide groups occupy two of the equatorial sites, which allows the f-Bu groups to better extend into space without causing serious repulsive contacts. The metal center in this compound has an unusually low coordination number of five.132... 

Potential-energy (reaction) surface — is a geometric hypersurface on which the potential energy of a set of reactants is plotted as a function of the coordinates representing the molecular geometries of the system. 

Speciation encompasses both the chemical and physical form an element takes in a geochemical setting. A detailed definition of speciation includes the following components (1) the identity of the contaminant of concern or interest (2) the oxidation state of the contaminant (3) associations and complexes to solids and dissolved species (surface complexes, metal-ligand bonds, surface precipitates) and (4) the molecular geometry and coordination environment of the metal.5 The more of these parameters that can be identified the better one can predict the potential risk of toxicity to organisms by heavy metal contaminants. Prior to the application... 

In all ab initio calculations so far the transition state is early in the reaction coordinate, the C —O distance is greater than 1.9 A and the molecular geometry of ethene is only slightly distorted the dihedral angle H —C — C —H is calculated to be more than 173 . It is therefore not surprising that thermodynamic stabilities (MM250 calculations, see Table 1) of diastereomeric epoxides correlate badly with observed diastereoselectivities of their formation. 

Of great importance is the nature of surface bonding of intermediates to the metal this depends very much on the geometry and orientation of the crystal plane on which the chemisorption takes place, and on the orientation and symmetry of emergent orbitals (especially dsp hybrid orbitals at transition metal surfaces) at the metal surface as emphasized and illustrated by Bond (24, 7) (Fig. 5 A). These factors determine the geometry of coordination of the adspecies at the catalyst or electrocatalyst surface. Since that work (41), a great many papers have appeared on molecular-orbital calculations for bonding at surfaces and on surface states and electron-density distributions. 

Auf der Heyde, T, P. E., and Biirgi, H.-B. Molecular geometry of d five-coordination. 2. Cluster analysis, archetypal geometries, and cluster statistics. Inorg. Chem. 28, 3970-3981 (1989),... 

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