Octahedral molecule structure

When a copper(II) salt dissolves in water, the complex aquo-ion [Cu(H2p)6P is formed this has a distorted octahedral (tetragonal) structure, with four near water molecules in a square plane around the copper and two far water molecules, one above and one below this plane. Addition of excess ammonia replaces only the four planar water molecules, to give the deep blue complex [Cu(NH3)4(H20)2] (often written as [Cu(NHj)4] for simplicity). TTo obtain [Cu(NH3)6], water must be absent, and an anhydrous copper(II) salt must be treated with liquid ammonia. 

A transargononic structure for sulfur, with six bonds formed by sp3d2 hybrid orbitals, was suggested for sulfur in the octahedral molecule SF6 long ago, and also for one of the sulfur atoms, with ligancy 6, in binnite (Pauling and Neuman, 1934). Some transargononic structures of metal sulfides have been proposed recently by Franzen (1966). 

C09-0103. How many different structural isomers are there for octahedral molecules with the general formula A Xz Draw three-dimensional structures of each. 

Telluric acid is a white sohd the crystal structure of which is built up of discrete regular octahedral molecules of Te(OH)6. It can conveniently be obtained by oxidizing TeC>2 in aqueous solution by, for example, KMn04. Anhydrous telluric acid can be crystallized in cubic, tetragonal, and monoclinic modifications. Structural data exist for the cubic and monoclinic forms. They both consist of discrete Te(OH)6 molecules that are linked together by hydrogen bonds. 

Our results add little to the question of the structure of ihe xenon hexafluoride molecule. The polarized Raman line al 621 cm could be assigned to the v, (a,) stretch of an octahedral molecule, and the depolarized line at 508 cm to V2 e,) the intensity pattern (v2 is comparable with i/ ) is very reminiscent of the Raman spectra of some isoelectronic molecules which are octahedral, viz. the hexahalogenotellurates(lV). Octahedral symmetry, however, cannot be reconciled with the complicated infrared spectrum of XeFs vapor, at least in the approximation of a simple harmonic force field. Pitzer and Bernstein have in any case provided persuasive evidence for XeFj monomer being substantially distorted in the Ti. bending mode from octahedral symmetry. This is in essential agreement with the bonding model proposed by Bartell and Gavin. ... 

The possible structures may be classified in terms of the coordination number of the central atom and the symmetry of the resulting molecule (Fig. 6.17). Two groups about a central atom will form angular (p2 orbitals, C, symmetry) or linear sp hybrid, D , symmetry) molecules three will form pyramidal (p, C3,) or trigonal planar (sp, Dy) molecules four will usually form tetrahedral (sp, Tj) or square planar (dsp, five usually form a trigonal bipyramidal (Dy,), more rarely a square pyramidal (C4,) molecule (both dsp hybrids, but using different orbitals, see Table 6.2) and six groups will usually form an octahedral molecule (d sp, O,). 

Structural studies have been made of several of these compounds. Ru (CO)4l2 forms octahedral molecules with the I atoms in cis positions (Ru—C, 2-01 A, Ru—I, 2-72 A), and a similar configuration has been assigned to Fe(CO)4l2 on the basis of i.r. evidence. The structure of [Rh(CO)2Cl]2 is more complex. This compound is dimeric in solution and also in the crystal, in which the dimers are bonVed into infinite chains by Rh-Rh bonds as shown in Fig. 22.10(a). To account for the diamagnetism it has been suggested that bent metal-metal bonds are formed by overlap of d sp orbitals at an angle of 56°. 

Platinum(V) fluoride is a tetramer (structurally like 22.5) PtFg is a red solid and has a molecular structure consisting of octahedral molecules neutron powder diffraction data confirm little deviation from an ideal octahedral structure. The hexafluoride is a very powerful oxidizing agent (equation 22.127, and see Section 5.16) and attacks glass. The oxidizing power of the second row rZ-block hexafluorides... 

Fig. 3.2. A scheme cf an octahedral molecule of liquid water structure [4]...

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