Cationic structures structural analysis

Compounds of the same stoichiometry type usually have the same type crystal structure within the row of alkali metals K - Rb - Cs rarely the same type structure with sodium-containing analogues and never ciystallize similarly with lithium-containing compounds. The crystal structure analysis of different fluoride and oxyfluoride compounds clearly indicates that the steric similarity between all cations and tantalum or niobium must be taken into account when calculating the X Me ratio. 

As well as the neutral compounds, also cationic complexes are available from chlorosilyl compounds by chloride abstraction. One example 12 has been characterized by x-ray structure analysis (Fig. 2). 

Attempts to prepare related hpp complexes of tantalum were only partially successful. Reaction of 2 equivalents of either (hpplSiMes or in situ generated Li[hpp] with Tads afforded a solid that analyzed correctly for the compound (hpp)2TaCl3. X-ray structural analysis of the crystallized product identified the coordination isomer [Ta(hpp)4][TaCl6], with a distorted dodecahedral cation and a regular octahedral anion (Figure 28). °... 

X-ray structural analysis of the methylsulfate compound indicates the orthorhombic crystal unit cell contains two translationally inequivalent cations positioned on mirror planes and tilted at 3 ° relative to the two-fold screw (c) axis (23). This is a compromise orientation for simultaneously, rather than individually, maximizing x ccc and x /> bbc in this polar structure. This structure is therefore consistent with the extremely large SHG intensity reported in Table 1 while, also consistently, preliminary x-ray data show the perrhenate and tetrafluoroborate salts to be isostructural (23.). Details of the packing... 

What shape would an early transition-metal hydride adopt if the ionic component were reduced Structural analysis of the cation HfH3+ (which is isovalent with LaH3) provides insight. The molecular cation exhibits bond angles (98.1°) that are nearly 10° less than those of LaH3, even though the Hf—H bond ionicity (lOOcHf2 = 36.35%) still deviates appreciably from the covalent limit. 

In order to obtain more information about the receptor-active conformation of muscimol, X-ray structure analysis, and ab initio quantum chemical studies have been applied to this compound (14). The flexibility of muscimol exclusively resides in the side chain (O-C-C-N bond) and a calculated potential energy curve for the rotation about this bond of muscimol in its zwitterionic form is shown in Fig. 3. These studies have demonstrated that in order for muscimol to obtain the conformation displayed by THIP, a conformational energy of 8.9 kcal/mol is required, which makes it less likely that the receptor-active conformation of muscimol corresponds to that of THIP. On the contrary, the conformation of THIP seems to mimic a high-energy conformation of muscimol as shown on the energy curve in Fig. 3, where the dihedral angles corresponding to the solid-state conformations of the muscimol zwitterion and the THIP cation are denoted. 

In the course of elaboration of effective new synthetic routes, the compound 63 had been synthesized <1999JHC183>. X-Ray structure analysis provided a final and firm proof of the structure and, thereby, the applicability of the invented method. Rusinov et al. < 1998ZOR290> investigated the structures of the cation of salt 64 and the zwitterionic compound 65 obtained by an addition of triazolopyrimidine derivatives on A -methylpyridinium compounds. The cation 64 was found to form hydrogen-bonded dimers, whereas 65 formed a co-crystal with acetonitrile. 

The formula as deduced from chemical and X-ray structural analysis is Na lgSi C S There is an open framework of Si04 tetrahedra with shared corners. Some silicon ions are replaced by aluminium ions, however, and to preserve electrical neutrality sodium cations are needed. These are in excess and the overall balance is maintained by the S2, S22 and S32- ions present. Consequently, chemical formulae containing fractional proportions of elements are possible. 

The first derivative of carba-nido-tetraboranes(7), 16a, was prepared by reaction of anionic 17 with iodomethane and characterized by NMR spectroscopy and by model computations (Scheme 3.2-10) [28]. The structurally analyzed 16b is obtained by deuteration of the dianion 10a2 [20] mentioned in Section 3.2.2.2. The results of an X-ray structural analysis of its dilithium salt are discussed in Section 3.2.8.3. The lithium cations are coordinated side-on to the B-B 2c2e bonds just as predicted for the aromatic U2B3H3 [6]. Obviously, (Li+)210a2 is a 2e homoaromatic. Since the positions of the lithium cations resemble those of the deuter-... 

Takano S, Tsuji K (1983) Analysis of cationic and amphoteric surfactants. III. Structural analysis of imidazolinium cationic surfactants. J Am Oil Chem Soc 60 870... 

---