Prisms, trigonal

Icosahedron Complex Trigonal prism Trigonal prism... 

Porterfield. W. W., 295 Positive oxidation states, halogens in, 837-848 Posttransition metals, 28. 876 Potassium, 309, 582-587 Potentials, electrode, 378-383 Pourbaix diagram, 591-592 Praseo complex, 388,491, 493 Predominance area diagram, 591 Prewitt, C. T., 116-117 Principal axis, 51 Prism, trigonal prism, 489-491 Probability function, 13 Prosthetic group, 919 Proteins, and blue copper proteins, 912-916 Proton... 

Figure 1.1 Top Quartz crystal exhibiting the true symmetry of the crystal class to which quartz belongs. Bottom The forms comprising such a quartz crystal. From left to right, the hexagonal prism, trigonal dipyramid, rhombohedron, and trigonal trapezohedron.

Trigonal trapezohedron, rhombohedron, trigonal dipyramid, ditrigonal prism, hexagonal prism, trigonal prism, pinacoid Low quartz... 

Figure 2-21. Examples of m-n m symmetries from the left, pentagonal prism trigonal bipyramid bicone cylinder.

Yellow prisms (trigonal trapazohedral) from alcohol. d]s 1.23. mp 95°. bp 346-348° bp12 188°. Absorption spectrum Hantzsch, Schwiete, Ber. 49, 216 (1916). uv max (ethanol) 260 nm (e 22,000). Infrared in chloroform 5.93 6.22 6.8S Insol in water sol in alcohol, ether, chloroform, ethyl acetate, benzene, toluene, nitrobenzene. 

The crystal stmcture of the calcium fluoroapatite has two different crystallographic sites for the Ca " ion. The Ca(I) site has a threefold axis of symmetry and is coordinated to six oxygen ions at the vertices of a distorted trigonal prism. The Ca(Il) ions are located at the corners of equilateral... 

The structures of metal-rich borides can be systematized by the schematic arrangements shown in Fig. 6.6, which illustrates the increasing tendency of B atoms to catenate as their concentration in the boride phase increases the B atoms are often at the centres of trigonal prisms of metal atoms (Fig. 6.7) and the various stoichiometries are accommodated as follows ... 

Figure 6.6 Idealized patterns of boron catenation in metal-rich borides. Examples of the structures (a)-(f) are given in the text. Boron atoms are often surrounded by trigonal prisms of M atoms as shown in Fig. 6.7.

The radius of the 24-coordinate metal site in MBs is too large (215-225 pm) to be comfortably occupied by the later (smaller) lanthanide elements Ho, Er, Tm and Lu, and these form MB4 instead, where the metal site has a radius of 185-200 pm. The structure of MB4 (also formed by Ca, Y, Mo and W) consists of a tetragonal lattice formed by chains of Bs octahedra linked along the c-axis and joined laterally by pairs of B2 atoms in the xy plane so as to form a 3D skeleton with tunnels along the c-axis that are filled by metal atoms (Fig. 6.11). The pairs of boron atoms are thus surrounded by trigonal prisms of... 

Figure 7.12 (a) Part of a layer of Al(OH)3 (idealized) the heavy and light open circles represent OH groups above and below the plane of the A1 atoms. In a-Al(OH)3 the layers are stacked to give approximately hep. (b) Structure of y-Al(OH)3 viewed in a direction parallel to the layers the OH groups labelled C and D are stacked directly beneath A and B. The six OH groups A, B, C, D and B, D (behind B and D), form a distorted H-bonded trigonal prism. 

Figure 7.18 (a) 1,4,7,10-letraazacyclododecane triacetic acid, (LH3). (b) Structure of the 7-coordinate compiex InL] the coordination poiyhedron (shown in white) comprises a trigonal prism of 4N and 20 capped on one of its quadrilateral faces by the third O atom. 

A range of shiny metallic compounds featuring trigonal planar anions SnX3 (X = As, Sb, Bi) have been characterized with composition M6(SnX3)Oo.5 (M = Rb, Cs) the Sn and X atoms in SnX3 (isostructural with C03 ) are coordinated by trigonal prisms of 6M+, and the ions occupy octahedral sites in the M+ lattice. 

Ms " clusters have 12 framework bonding electrons as has [BsHs]- (p. 161) the anions are also isoelectronic with the well-known cation [Bis]. Similarly, the alloy NaSn. 2.23 reacts with cryptand in ethylenediamine to give dark-red crystals of [Na(ciypt)]4 [Sng] the anion is the first example of a C41, unicapped Archi-median antiprism (Fig. 10. lOc) and differs from the >3/, structure of the isoelectronic cation [Bis] + which, in the salt Bi+[Bi9] +[HfCl6]5 (p. 591), features a tricapped trigonal prism, as in [BgHg] " (p. 153). The emerald green species [Pb9] , which is stable in liquid NH3 solution, has not so far proved amenable to isolation via ciyptand-complexed cations. 

The influence of electron-count on cluster geometry has been very elegantly shown by a crystallographic study of the deep-red compound [K(ctypt)]g [Ge9]- [Ge9] .2.5en, prepared by the reaction of KGe with cryptand in ethylenediamine. [Ge9] has the C4, unicapped square-antiprismatic structure (10.10c) whereas [Ge9]- , with 2 less electrons, adopts a distorted Dit, structure which clearly derives from the tricapped trigonal prism (p. 153).The field is one of... 

MP (M = Cr, Mn, Fe, Co, Ru, W) distorted trigonal prismatie eoordination of P by M plus two rather short eontaets to P atoms in adjaeent trigonal prisms, thus building up a eontinuous ehain of P atoms NiP is a distortion of this in whieh the P atoms are grouped in pairs rather than in ehains (or isolated as in VP). 

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