Distortions trigonal

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... 

Blue copper in azutin Trigonal distorted toward tetrahedral... 

Fig. 5. The piezospectroscopic behavior of the two ls-like levels of differently oriented, trigonal shallow acceptor complexes, based on the equivalent stress model, (a) Trigonal distortion equivalent to a stress of + 0.205 kbar (tensional). (b) Trigonal distortion equivalent to a stress of —0.810 kbar (compressional). Roman numerals denote the four possible orientations of the complexes. A4 and A5 6 denote the representations of C3v according to which the states transform in the absence of externally applied stress. The energy shifts are shown for externally applied compressional stress under applied tensional stress, the behavior of (a) and (b) is reversed, as explained in the text.

Gas phase photoelectron studies [57] have shown that [Fe(HB(pz)3)2] is in the high-spin state at 400 K as is also the case [58] for [Fe(B(pz)4)2] between 480 and 560 K. Although both complexes are in the high-spin state, the steric effects mentioned above for [Fe(B(pz)4)2] are revealed as a more pronounced trigonal distortion for this complex as compared to [Fe(HB(pz)3)2]. 

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 electrochemical reversibility of the Cu(II)/Cu(I) process E° = + 0.36 V vs. NHE) is in agreement with the X-ray structure of reduced plastocyanin, which shows that the active site maintains its trigonally distorted tetrahedral geometry with a slight lengthening (of about 0.1 A) of the Cu-N distances. 

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. 

Figure 7.18. Comparison of experimental and predicted phase equilibria in the system CaC03-MgC03 using CVM in the tetrahedron approximation for a trigonally distorted f.c.c. Ising lattice. Semi-quantitative agreement is achieved for the calcite-dolomite segment but the Mg-rich side of the diagram indicates the need to include a more complex model (Burton and Kikuchi 1984b).

This compound is isostructural with brucite (Mg(OH)2) and Cdl2. The unit cell is hexagonal with a = 0.3258 nm and c = 0.4605 nm. The structure consists of sheets of corner-sharing, trigonally distorted Fe(OH)6 octahedra stacked along the [001] direction. The Fe" ions occupy only half the available octahedral interstices and this results in a structure in which each filled layer of sites alternates with an empty layer of sites. The OH radical behaves as a single entity. Amakinite is a rare mineral of the composition (Fe,Mg,Mn)(OH)2, also with brucite structure. Fe(OH)2 is readily oxidized by air and even by water, upon which the colour changes from white to brownish. The structure can be maintained up to a replacement of one tenth Fe" by Fe " (Bernal et al., 1959). 

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. 

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