Potassium tris

Iodine is a dark-coloured solid which has a glittering crystalline appearance. It is easily sublimed to form a bluish vapour in vacuo. but in air, the vapour is brownish-violet. Since it has a small vapour pressure at ordinary temperatures, iodine slowly sublimes if left in an open vessel for the same reason, iodine is best weighed in a stoppered bottle containing some potassium iodide solution, in which the iodine dissolves to form potassium tri-iodide. The vapour of iodine is composed of I2 molecules up to about 1000 K above this temperature, dissociation into iodine atoms becomes appreciable. 

Synthetically useful stereoselective reductions have been possible with cyclic carbonyl compounds of rigid conformation. Reduction of substituted cyclohexanone and cyclopentan-one rings by hydrides of moderate activity, e.g. NaBH (J.-L. Luche, 1978), leads to alcohols via hydride addition to the less hindered side of the carbonyl group. Hydrides with bulky substituents 3IQ especially useful for such regio- and stereoselective reductions, e.g. lithium hydrotri-t-butoxyaluminate (C.H. Kuo, 1968) and lithium or potassium tri-sec-butylhydro-borates or hydrotri-sec-isoamylborates (=L-, K-, LS- and KS-Selectrides ) (H.C. Brown, 1972 B C.A. Brown, 1973 S. Krishnamurthy, 1976). 

A noteworthy development is the use of KH for complexing alkylboranes and alkoxyboranes to form various boron hydrides used as reducing agents in the pharmaceutical industry. Potassium tri-j -butylborohydride [54575-50-7] KB(CH(CH2)C2H )2H, and potassium trisiamylborohydride [67966-25-0] KB(CH(CH2)CH(CH2)2)3H, are usefiil for the stereoselective reduction of ketones (66) and for the conjugate reduction and alkylation of a,P-unsaturated ketones (67). 

Interaction of the thiophene-containing organomercury compounds 272 (R = H, Me, Et) [74MI1, 79JCS(D)2037] with potassium tris(3-methylpyrazolyl) borate (KTp ) yields 273 [96JOM(515)213],... 

Triphenylsulfonium tetrafluoroborate [(C6Hs)3 S" BF4 ] is used instead of diphenyl iodonium chloride to give phenyl radical as the initiating species. Potassium [tris(oxalato) cobaltate) (III)] with diphenyl iodonium chloride also has been used as the photoinitiator of acryl-... 

In a potassium acetate-acetic acid medium, 2-fluoro- and 4-fluoroanisole can be oxidized at platinum to afford 2-acetoxy- and 4-acetoxyanisole, respectively [19]. Using a platinum anode in a trifluoroacetic acid-potassium tri-fluoroacetate solution, Blum and Ny-berg [20] electrooxidized hexafluoroben-zene to tetrafluorobenzoquinone in 75% yield, and octafluoronaphthalene was converted into hexafluoronaphthoquinone in 60% yield. 

The action of bromine on potassium tris-malonatocobalt(iii) leads only to decomposition however, with iV-bromosuccinimide in CC, K3[Co(bromo-malonatelj] is formed.The structure of [Co(amidoxalato)2(H20)2]2H20 shows it to have a rra s-octahedral structure, the amido-oxalate ligands chelating via one carboxylate oxygen and the amidic oxygen. 

Replacement of hydrogen by alkyl groups gives compounds like lithium triethylborohydride (Super-Hydride ) [100], lithium tris sec-butyl)borohydride [101] (L-Selectride ) and potassium tris sec-butyl)borohydride (K-Selectride ) [702], Replacement by a cyano group yields sodium cyanoborohydride [103], a compound stable even at low pH (down to 3), and tetrabutylammonium cyanoborohydride [93],... 

After the resolution of 1-2-chloro-ammino-diethylenediamino-cobaltie chloride many analogous resolutions of optically active compounds of octahedral symmetry were carried out, and active isomers of substances containing central cobalt, chromium, platinum, rhodium, iron atoms are known. The asymmetry is not confined to ammines alone, but is found in salts of complex type for example, potassium tri-oxalato-chromium, [Cr(Ca04)3]K3, exists in two optically active forms. These forms were separated by Werner2 by means of the base strychnine. More than forty series of compounds possessing octahedral symmetry have been proved to exist in optically active forms, so that the spatial configuration for co-ordination number six is firmly established. 

A variety of alkali metal and metallocene-containing magnesium amides are known. Thus, attempted metallation of ferrocene using potassium tris(amido)magnesiate KMg N-(SiMe3)2 3 unexpectedly led to n-coordination of neutral ferrocene moieties to a pota-... 

A. A. Noyes 5 to the belief that the number of molecules in the soln. is not changed by the addition of more iodine because polyiodides are formed MI+mI2=MI2 +i. Y. Osaka showed that the rise of the f.p. which occurs when iodine is added to hydriodic acid or to aq. soln. of potassium iodide is proportional to the amount of iodine added, and is greater for hydriodic acid than for the potassium salt. Hence, the total concentration of the ions and of unionized molecules is decreased by the addition of iodine. A. A. Jakowkin inferred from the partition coeff. of iodine in dil. soln. that potassium tri-iodide was formed, and that with more cone. soln. still more complex polyiodides are produced. Still further, the change in the partition coeff. of iodine between aq. soln. of potassium iodide and nitrobenzene led H. M. Dawson and R. Gawler to infer that polyiodides as high as potassium ennea-iodide, KI9, are probably present in soln., although no such compound has been obtained in the solid state. H. L. Wells and H. L. Wheeler and others, however, have prepared several solid alkali polyiodides for example ... 

The lowering of the conductivity is not attributed to a change in the degree of ionization of the soln., but rather to the decreased mobility of the anions during the change from I to I3. At 25°, the mobility of the T-ion is 76 5 and of the I3 -ion, 410. The diffusion constant of I3 -ions, according to E. Brunner, is 0 9 per sq. cm. per day at 20°, that is, approximately the same as that of free iodine. When iodine dissolves in potassium iodide soln., W. C. Bray and G. M. J. McKay calculate that there is an expansion of 0 2376 c.c. per gram of iodine or 60 31 c.c. per mol. of iodine per litre of soln. The colour of dil. soln. of potassium tri-iodide is yellowish-brown which with increased cone, becomes very dark blue, almost opaque, in thin layers dark red. 

Potassium di-iodate. Potassium tri-iodate. Potassium molybdamo- Potassiumsulphato-... 

D. L. Chapman, for potassium tri-iodide. 0. Gropp measured the effect of temp, on the conductivity of solid and frozen soln. of sodium iodide. For the effect of press, on the electrical properties, vide alkali chlorides. A. Reis found the free energy for the separation of the ions of K1 to be 144 lrilogrm. cals, per mol. for iN al, 158 Lil, 153 and for HI, 305. S. W. Serkofi 35 measured the conductivity of lithium iodide in methyl alcohol P. Walden, of sodium iodide in acetonitrile P. Dutoit in acetone, benzonitrite, pyridine, acetophenone. J. C. Philip and H. R. Courtman, B. B. Turner, J. Fischler, and P. Walden of potassium iodide in methyl or ethyl alcohol J. C. Philip and H. P. Courtman in nitromethane P. Dutoit in acetone. H. C. Jones, of rubidium iodide in formamide. S. von Lasczynsky and S. von Gorsky, of potassium and sodium iodides in pyridine. A. Heydweiller found the dielectric constants of powdered and compact potassium iodide to be respectively 3 00 and 5 58. 

Table 81 The Electronic Spectrum of Potassium Tris(oxalato)chromate(III) (after ref. 889)...

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