Planar compounds white

Orthoboric acid, B(OH)3, is the normal end product of hydrolysis of most boron compounds and is usually made ( 160 000 tonnes pa) by acidification of aqueous solutions of borax. Price depends on quality, being 805 per tonne for technical grade and about twice that for refined material (1990). It forms flaky, white, transparent crystals in which a planar array of BO3 units is joined by unsymmetrical H bonds as shown in Fig. 6.25. In contrast to the short O—H O distance of 272 pm within the plane, the distance between consecutive layers in the ciystal is 318 pm, thus accounting for the pronounced basal cleavage of the waxy, plate-like ciystals, and their low density (1.48 g cm ). B(OH)3 is a very weak monobasic acid and acts exclusively by hydroxyl-ion acceptance rather than proton donation ... 

Figure 8.12 An illustration of the planar (TIN)2 ring in the compound [(TI N(SiMe3)2 )2]. Thallium, nitrogen and silicon atoms are shown as black spheres and carbon atoms are white. Selected bond lengths TI1-N1 2.581(7), TI1-N2 2.576(7) A...

D. J. White, J. T. Stewart, and I. L. Honigberg, Quantitative Analysis of diazepam and related compounds in drug substance and tablet dosage form by HPTLC and scanning densitometry, J. Planar Chromatogr., 4 413 (1991). 

Boric acid, B(OH)3, is the archetype and primary source of oxo-boron compounds. It is also the normal end product of hydrolysis of most boron compounds. It forms flaky, white and transparent crystals, in which the BO3 units are joined to form planar layers by O-H- O hydrogen bonds, as shown in Fig. 13.5.1. 

The one form of tellurium is silvery-white, semimetallic, and isomorphous with grey Se. Like the latter it is virtually insoluble in all liquids except those with which it reacts. Even though Te8 rings are not found in elemental tellurium, they do occur in the compound C Te, 5 which also contains unusual planar nets of Te atoms. 

Copper(I) Carboxylates, Triflate, Alkoxides, and Dialky lamides. Thecarbox-ylates have varied structures. The acetate that is obtained as white air-sensitive crystals by reduction of Cu11 acetate by Cu in pyridine or MeCN has a planar chain structure (17-H-I). By contrast the trifluoroacetate [Cu02CCF3]4-2C,H6, and benzoate [Cu02CPh]4 complexes are tetramers with bridging carboxylates as in (17-H-II). This is only one type of Cut polynuclear structure (see later). There are also bridged pyrazole and pyrazolylborate compounds. 

A fascinating analogy between cp and Ps became apparent by the isolation of the mixed ferrocene cp Fe(P5), where cp represents pentamethylcyclopentadienyl and (P5) the planar, strictly pentagonal phosphoras unit (52). The compound is prepared in the thermolysis of [cp Fe(CO)2]2 in the presence of white phosphorus. The Ps unit, which clearly acts as a six-electron donor in this mononuclear complex, can also function as a central unit in a cationic triple-decker cation [(cp)Fe(P5)Fe(cp )]+ (53).i ... 

The reaction between catechol and Si/Cu alloy at high temperature and pressure affords the spiro compound (9) as a glassy white material.The structure of (9) has been the subject of some dispute. Although it was originally thought to have a planar geometry at silicon this has not been confirmed, and it is likely that it has a normal tetrahedral arrangement as found in the related (10) and (H).251,252... 

---