Octahedral shape

S is the central atom. All atoms have zero formal charge in the Lewis structure. This molecule is of the AX6 type it has an octahedral electron-group geometry and an octahedral shape. Even though each S — F bond is polar toward F, the bonds symmetrically oppose each other resulting in a molecule that is nonpolar. 

Figure 15. The HRTEM micrograph of three MoS2 nanoparticle with octahedral shape and its image simulation (77).

Determine if the molecule XeFe will have an octahedral shape. 

Figure 2.15 Schematic representation of the silica supported metallic particle with a cubo-octahedral shape (a) and a real particle size distribution of platinum nanoclusters supported on silica (b).

The SbF6 ion has a central antimony atom with a ground state of 5s25p2 which is trivalent. If the 5s electrons were to be unpaired and one promoted to a 5d orbital the antimony would then be five-valent. If it accepted an electron to make it Sb and the electron was accommodated in another 5d orbital the ion would be six-valent and could accept the six electrons from the six ligand fluorine atoms to give a valence shell of six a pairs. This would indicate that the ion should have a regular octahedral shape. 

By linking edge-sharing octahedra to form a layer as in Fig. 16.8, all X atoms act as bridging agents, and every one of them simultaneously belongs to two octahedra. This kind of layer encloses voids that have an octahedral shape (see also the figure on the cover). The composition of the layer is MX3 Numerous trichlorides, tribromides... 

Figure 1. Optical micrograph of an as-grown crystal of Py-D3C exhibiting a characteristic truncated octahedral shape. Domains are apparent in transmitted cross-polarized light.

In SF6, six sp d orbitals are needed to provide an octahedral shaped molecule. 

Platinum (IV) Structures. The oxidation state of the platinum atom in platinum coordination compounds determines the steric configuration of the molecule platinum(II) structures are planar molecules, while platinum(IV) derivatives assume an octahedral shape. Though it was hoped that these differences could be used to circumvent platinum resistance, the two compounds developed in the clinic, iproplatin and ormaplatin, have not proven useful. In the case of the former, testing in Phase-II trials failed to reveal activity. In the case of ormaplatin, the platinum(IV) configuration is not maintained under biological conditions conversion to a platinum(II) metabolite occurs within minutes [14], A series of novel platinum(IV) and mixed ammine/amine derivatives being developed at the Institute for Cancer Research are described in this volume by Kelland. 

Spinel is another simple oxide mineral. It is commonly seen today as a synthetic and may be any color. Natural red spinel was most prized as a gem, and usually was used as an imitation of ruby. Some notable pieces in the British and Russian crown jewels include large uncut spinels. These crystals are a deep red color and are distinctive because of their rough octahedral shape. 

Figure 2-60. Shapes and various modes of linkage of truncated octahedral-shaped sodalite units [97], Used by permission from Plenum Press and Brian Beagley.

The versatility of transition-metal-ligand combinations in stabilizing localized, partially localized and delocalized cluster bonding is evident in the three examples discussed to this point. But we still have no analog of a late metal-carbonyl cluster that follows the main-group counting paradigm for an octahedral shape. Centered zirconium chloride clusters provide an example of an octahedral cluster with seven... 

The natural octahedral shape for a hoinopolar semiconductor, with a possible truncation of the corners. 

So-called superlattices of 5mn alkylthiolate protected silver particles having truncated octahedral shapes as well as thiol-stabilized 5 6 mn gold particles can be obtained from solution. Fractional crystallization is a very usual method to separate chemical compounds from other compounds and impurities. Mixtures of thiolate stabilized gold nanoparticles between 1.5 and 3.5 nm could successfully be fractioned into real monodisperse species containing 140, 225, 314, and 459 atoms. 2D assemblies have also become available of these fcc-structured nanoparticles. The decisive criterion to successhilly fraction and crystallize metal nanoparticles is to protect them perfectly by strongly bound ligand molecules in order to avoid coalescence. 

Fig. 7 Cubo-octahedral shapes for different values of <100> growth rate/<111 > growth rate. ...

Complex Fluorides of Platinum iv).— Although hexafluoroplatinic(iv) acid cannot be synthesized in water, its hydrolysis is so slow that the alkali, alkaline-earth, and rare-earth salts have aU been made from the acid in aqueous solution. The crystal structure of the potassium salt shows that the hexafluoroplatinate(iv) ion possesses the regular octahedral shape expected for a dizg electron configuration. 

The recently synthesized Au(V) complex fluorides of the form A AuFjwith A = Xe2F, XeRJ, and Cs have been studied by Mossbauer spectroscopy with the 77.3 keV gamma resonance of Au. The values obtained for isomer shift and electric quadrupole interaction are in harmony with the assigned oxidation state Au(V), as well as with the octahedral shape of the AuFj anion. 

Werner s synthesis and separation of optical isomers proved the octahedral shape conclusively, because none of the other six-coordinate geometries could have similar optical activity. 

Six is the most common coordination number. The most common structure is octahedral some trigonal prismatic structures are also known. If a metal ion is large enough to allow six ligands to fit around it and the d electrons are ignored, an octahedral shape results from VSEPR arguments. Such compounds exist for all the transition metals with to d configurations. 

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