Prismatic structures

Again, fluoro and oxo complexes of rhenium predominate. The reaction of KF and ReFe in an inert PTFE vessel yields pink K2[ReFs], the anion of which has a square-prismatic structure hydrolysis converts it to K[ReOFs]. 

The trigonal prismatic structure shown in the illustration was once proposed for the [CoC12(NH,)4] complex. Use the fact that only two isomers of the complex are known to rule out the prismatic structure. 

If the prismatic structure were correct, six structural isomers should exist, not two, four of which are shown here (X = NH,) ... 

The versatile binding modes of the Cu2+ ion with coordination number from four to six due to Jahn-Teller distortion is one of the important reasons for the diverse structures of the Cu-Ln amino acid complexes. In contrast, other transition metal ions prefer the octahedral mode. For the divalent ions Co2+, Ni2+, and Zn2+, only two distinct structures were observed one is a heptanuclear octahedral [LnM6] cluster compound, and the other is also heptanuclear but with a trigonal-prismatic structure. 

The fact that the trigonal prismatic structure does not afford the correct number of isomers is a clear indication that the ion actually adopts some other structural form (i.e., the theoretical model is contradicted by the experimental result). We know now of course, that this ion has an octahedral structure and as a result, it can exist only in cis and trans configurations. 

All attempts to produce optical isomers of [Co(en)3]3+ based upon a trigonal prismatic structure are shown below. The ethylenediamine ligand appears as an arc in each diagram below ... 

Btknzl 12.5-20 cm light yellowish brown (10YR 6/4) sandy clay loam, moderate medium prismatic structure... 

Btknz3 27.5—45 cm strong brown (7.5YR 5/6) clay loam, strong medium prismatic structure... 

A 2 2.5-25 cm very dark grayish brown (10YR 3/2) clay, moderate coarse prismatic structure... 

Nine-coordinate (each NOj group is bidentate) tricapped trigonal prismatic structure... 

Different bismuth clusters are apparently formed in reactions between bismuth and bismuth trichloride-aluminum trichloride mixtures, from which the salts (Big) " (AICl4 )3, and (Bi8) + (AICl4 )2 have been isolated 43). A trigonal-bipyramidal structure was predicted for Big (a closo 6 skeletal bond pair system cf. C2B3Hg), and a square anti-prismatic structure for Bi8 , as appropriate for an arachno 8-atom, 11 skeletal bond pair cluster. Similar polyhedral shapes appear likely for other clusters not only of bismuth but also of other heavy main group metals (the anion Pbg ", for example, is isoelectronic with Bi9 " ). 

Prismatic structure layer the layer consisting of polygonal rhombic prismatic aragonite crystals perpendicular to the inner surface of the shell. 

Composite prismatic structure the c-axis of rhombic prisms align parallel to the shell. The rhombic prism is an aggregation of aragonite needle crystals aligned in conical form in its elongation direction. 

S = solution, (e) Prismatic structure (f) foliated structure (g) crossed lamellar structure (h) complex crossed lamellar structure. 

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