Distorted octahedral complex

The compound Ag(TaF6)2 crystallizes in triclinic syngony with cell parameters (A, grad.) as follows a = 9.061, b = 5.607, c = 5.207, a = 118.7, p = 91.61, y = 102.3. Ag(TaF6)2 is composed of two separate layers made up of octahedral ions AgF64 and distorted octahedral complexes NbFe that are linked through the planes. 

Besides complexes of thiosemicarbazones prepared from nitrogen heterocycles, iron(III) complexes of both 2-formylthiophene thiosemicarbazone, 26, and 2-acetylthiophene thiosemicarbazone, 27, have been isolated [155]. Low spin, distorted octahedral complexes of stoichiometry [Fe(26)2A2]A (A = Cl, Br, SCN) were found to be 1 1 electrolytes in nitromethane. Low spin Fe(27)3A3 (A = Cl, Br, SCN) complexes were also isolated, but their insolubility in organic solvents did not allow molar conductivity measurements. Infrared speetra indicate coordination of both via the azomethine nitrogen and thione sulfur, but not the thiophene sulfur. The thiocyanate complexes have spectral bands at 2065, 770 and 470 cm consistent with N-bonded thiocyanato ligands, but v(FeCl) and v(FeBr) were not assigned due to the large number of bands found in the spectra of the two ligands. 

In the trigonal point group 3, the axis of quantization is chosen along the three-fold axis, while the x and y axes may be selected anywhere in the plane perpendicular to the z axis. In the point group 3m, which occurs for many distorted octahedral complexes, there are also vertical mirror planes. The relation to the cubic axes is described by the transformation... 

Electron Density Studies of Octahedral and Distorted Octahedral Complexes... 

Octahedral and distorted octahedral complexes of first-row transition metal atoms were subjected to X-ray charge density analysis in the pioneering studies of Iwata and Saito in the early 1970s (Iwata and Saito 1973). 

TABLE 10.5 Comparison of Orbital Populations in a Number of Octahedral and Distorted Octahedral Complexes (From Treatment with Zero 4s Population)... 

The highly distorted octahedral complex [mer-V (pic) 3] (pic = picolinic acid, a tryptophan metabolite) oxidizes over time to the [VO(pic)2] complex in aqueous solution [39]. Conductivity measurements revealed that the species is a nonelectrolyte, and voltammetry indicated a reversible oxidation at 0.635 V and reduction at — 1.01 V versus Ag/AgCl, values which are more positive than usually observed for comparable complexes. This feature was attributed to delocalization of d electrons [39]. 

As for V(III), trigonal prismatic complexes, and trigonally distorted octahedral complexes are not uncommon for V(IV) [56]. The ligand set exerts a stronger influence on the redox potentials, whether the coordination geometry is octahedral or trigonal prismatic, at least to a first approximation. A series of compounds made with tridentate and tetradentate ligands with N- and O-donor atoms such as the azophenol derivative shown in Fig. 8 has both reversible oxidations and reductions. 

Chromium(II) complexes of bipyridyls, terpyridyl and the phenanthrolines have been discussed in Section 35.2.2.1. Complexes of the ligands 2-aminomethylpyridine (pic, 2-picolyl-amine) and 8-aminoquinoline (amq), which have one heterocyclic and one amino nitrogen donor atom, have been prepared by methods similar to those in Scheme 10. The bis(amine) complexes are typical high-spin, distorted octahedral complexes, and the mono(amine) complexes, from their antiferromagnetic behaviour and reflectance spectra, are six-coordinate, halide-bridged polymers (Table 15).103 No tris(amine) complexes could be prepared so the attempt to find spin isomeric systems in octahedral chromium(II) systems was unsuccessful ([Cr(en)3]X2 are high-spin and [Cr(bipy)3]X3 and [CrX2(bipy)2] low-spin). 

Co11 complexes containing phosphoramides (O = P(NR2)3)591 iminophosphoranes (RN = PPh3)592 and phosphinates ( 02PR R2)593 are known, as are distorted octahedral complexes containing the neutral chelating ligands (171),m (172)595 and (173).596... 

The overwhelming tendency is for the EX5 molecules to interact with an electron donor (L) to give octahedral or distorted octahedral complexes, EX5L° . When L = X, which is perhaps the most important case, the strictly octahedral hexahalo anions (EX ) are obtained. 

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