Trigonally distorted octahedral

CsPuF6 was prepared and verified to be isostructural with corresponding compounds of uranium and neptunium. Its decomposition was studied in an inert gas atmosphere and in vacuum. Its spectrum has been measured in the region 400-2000 nm. The energy level structure of Pu5+ in the trigonally distorted octahedral CsPuF6 site was computed from a predictive model and compared with the observed spectrum. 

To start with a relatively simple case, Rb[Cd Ag(CN)2 3] (from RbCl, AgN03, Cd(N03)2, and NaCN in H20) is discussed. In its structure (P312, Z = 1), Cd and the rod-like N-coordinating NC—Ag—CN units create three independent, interpenetrating, 3-D frameworks Cd (symmetry 32 —Z)3) has trigonally distorted octahedral coordination (r(Cd—N) 232.4 pm). Rb occupies one of two types of trigonal channels.218... 

The complex shifts to high-spin on protonation of the apical amino groups. The structure of [Fe(NH3)2sar](N03)4.H20 is a trigonally distorted octahedral (0=29°). Unfortunately, because of the easy oxidation of the NH-CH2 functions to imines, this compound is very air-sensitive, making the spectroscopic characterization rather difficult. 

Oxide mineralogy may influence rates of reductive dissolution in several ways. Hematite (ct-Fe203) and maghemite (y-Fe203), for example, have the same stoichiometry but contain Fe(III) in quite different coordinative environments. Fe(III) in hematite occupies trigonally-distorted octahedral sites, while Fe(III) in maghemite is found in both octahedral and tetrahedral sites (42). Differences... 

The crystal structure of hexaureatitanium(iii)perchlorate has been determined. The structural details of the cations, which involve a trigonally distorted octahedral TiO unit (average Ti—O = 204 pm), are very similar to those found for this ion in the iodide. 

Ti + is able to create a timable laser in a sapphire lattice (Fabeni et al. 1991). It substitutes the ion of the host crystal in a trigonally distorted octahedral lattice site and is characterized by a strongly polarized band peaking at approximately 750 nm with a decay time of 3.1 ps (Fig. 5.40). 

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. 

Figure 4.10 Polarized absorption spectra of ruby (from Bums, 1984). The ruby formula is (AIq 99gCr0 002)203, and the spectra originate from crystal field transitions within Cr3+ replacing Al3+ ions in trigonally distorted octahedral sites in the trigonal corundum structure. Consequently, the spectra differ slightly for light polarized (a) parallel (Ellc) and (b) perpendicular (E c) to the c crystallographic axis. The group theoretical assignments of the absorption bands are also indicated. [Reproduced from Chemistry in Britain, 1984, p. 1004]...

Although the Schiffbase (pyrol)3tren) (17) formed by condensation of pyrrole-2-carboxaldehyde with 2,2, 2"-tris(ethylamino)amine is potentially heptadentate the neutral low-spin complex [Fe (py-rol)3 tren ] has a six-coordinate (trigonally distorted octahedral) structure, the distance between the metal atom and the central tertiary aliphatic nitrogen being greater than the van der Waals contact... 

As previously noted, spin cross-over behaviour is well established in iron(II) complexes and there are also examples involving iron(III) species. For example, a variety of iron(III) dithiocarbamate complexes of the type [Fe(S2CNR2)3j having a trigonally distorted octahedral geometry display high-spin/low-spin cross-over behviour 49,50 Little is known about the spin forbidden d-d transitions of iron(III) complexes due to near-UV charge transfer bands that tail into the visible part of the spectrum. Even simple iron(III) salts in aqueous media are yellow. 

The /3-diketonates resemble those of A1 rather than those of the lanthanides. Thus the acetylacetonate is normally anhydrous and may be sublimed at around 200°C it has a trigonally distorted octahedral structure. 

Reaction of Pb(ACAC)2 with two equivalents of HB(Arf)4 in CH2CI2 followed by HC(pz)3 or HC(3,5-Me2-pz)3 gives the complexes [L2Pb] 4 [B(Arf)4]2 (Arf=3,5-(CF3)2-C6H3). For the HC(pz)3 complex, the lead has a distorted octahedral geometry with a stereochemically active lone pair, while the complex with the more sterically encumbered HC(3,5-Me2-pz)3 has a trigonally distorted octahedral structure with a stereochemically inactive lone pair. ... 

Trigonally distorted octahedral Rh. Mean Rh—S 2.369 A Octahedral Rh atoms. 1 Rh 2 terminal dtc ligands, other Rh 1. Second Rh has 2 dtc ligands which have 1 end bridging... 

X is C or B, Y is H for Co[HCpz3] + or Co[HBpz3] +, pz for Co[BPz4]2. The symmetry of the molecule is and the ligand field is effectively trigonally distorted octahedral. Proton NMR spectra may be seen from the ligand nuclei. 

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