Hexacyano

The existence of anode and cathode areas can be seen by the following experiment. A few drops of phenolphthalein are added to a solution of potassium hexacyanoferrate(III) and hydrochloric acid added, drop by drop, until the solution is colourless. (The phenolphthalein turns pink due to hydrolysis of the potassium hexacyano-ferrate(III).) Drops of this solution, about 1 cm in diameter, are now placed on a sheet of freshly abraded steel when pink cathode areas and blue anode areas appear. 

Potassium hexacyano-ferrate(II). K,Fe(CN)(, Potassium hexacyano-ferrateilll), K3Fe CN)6 Potassium thiocyanate. K.CNS... 

Polyether Polyols. Polyether polyols are addition products derived from cyclic ethers (Table 4). The alkylene oxide polymerisation is usually initiated by alkah hydroxides, especially potassium hydroxide. In the base-catalysed polymerisation of propylene oxide, some rearrangement occurs to give aHyl alcohol. Further reaction of aHyl alcohol with propylene oxide produces a monofunctional alcohol. Therefore, polyether polyols derived from propylene oxide are not truly diftmctional. By using sine hexacyano cobaltate as catalyst, a more diftmctional polyol is obtained (20). Olin has introduced the diftmctional polyether polyols under the trade name POLY-L. Trichlorobutylene oxide-derived polyether polyols are useful as reactive fire retardants. Poly(tetramethylene glycol) (PTMG) is produced in the acid-catalysed homopolymerisation of tetrahydrofuran. Copolymers derived from tetrahydrofuran and ethylene oxide are also produced. 

These acids (51) are organic molecules that contain a plurality of cyano groups and are readily ionized to hydrogen ions and resonance-stabilized anions. Typical cyanocarbon acids are cyanoform, methanetricarbonitrile (5) 1,1,3,3-tetracyanopropene [32019-26-4] l-propene-l,l,3,3-tetracarbonitrile (52) 1,1,2,3,3-pentacyanopropene [45078-17-9], l-propene-l,l,2,3,3-pentacarbonitrile (51) l,l,2,6,7,7-hexacyano-l,3,5-heptatriene [69239-39-0] (53) 2-dicyanomethylene-l,l,3,3-tetracyanopropane [32019-27-5] (51) and l,3-cyclopentadiene-l,2,3,4,5-pentacarbonitrile [69239-40-3] (54,55). Many of these acids rival mineral acids in strength (56) and are usually isolable only as salts with metal or ammonium ions. The remarkable strength of these acids results from resonance stabilization in the anions that is not possible in the protonated forms. 

Similarity with cobalt is also apparent in the affinity of Rh and iH for ammonia and amines. The kinetic inertness of the ammines of Rh has led to the use of several of them in studies of the trans effect (p. 1163) in octahedral complexes, while the ammines of Ir are so stable as to withstand boiling in aqueous alkali. Stable complexes such as [M(C204)3], [M(acac)3] and [M(CN)5] are formed by all three metals. Force constants obtained from the infrared spectra of the hexacyano complexes indicate that the M--C bond strength increases in the order Co < Rh < [r. Like cobalt, rhodium too forms bridged superoxides such as the blue, paramagnetic, fCl(py)4Rh-02-Rh(py)4Cll produced by aerial oxidation of aqueous ethanolic solutions of RhCL and pyridine.In fact it seems likely that many of the species produced by oxidation of aqueous solutions of Rh and presumed to contain the metal in higher oxidation states, are actually superoxides of Rh . ... 

The Ni /CN system illustrates nicely the ease of conversion of the two stereochemistries. Although, as already pointed out, there is no evidence of a hexacyano complex, a square pyramidal pentacyano complex is known ... 

Heating with the following solids, their fusions, or vapours (a) oxides, peroxides, hydroxides, nitrates, nitrites, sulphides, cyanides, hexacyano-ferrate(III), and hexacyanoferrate(II) of the alkali and alkaline-earth metals (except oxides and hydroxides of calcium and strontium) (b) molten lead, silver, copper, zinc, bismuth, tin, or gold, or mixtures which form these metals upon reduction (c) phosphorus, arsenic, antimony, or silicon, or mixtures which form these elements upon reduction, particularly phosphates, arsenates,... 

To illustrate how the use of standard potentials may occasionally lead to erroneous conclusions, consider the hexacyanoferrate(II)-hexacyano-ferrate(III) and the iodide-iodine systems. The standard potentials are ... 

Meisel etal. [18-20] were the first to investigate how the addition of a polyelectrolyte affects photoinduced ET reactions. They found that charge separation was enhanced as a result of the retardation of the back ET when poly(vinyl sulfate) was added to an aqueous reaction system consisting of tris(2,2 -bipyridine)ruthenium(II) chloride (cationic photoactive chromophore) and neutral electron acceptors [21]. More recently, Sassoon and Rabani [22] observed that the addition of polybrene (a polycation) had a significant effect on separating the photoinduced ET products in an aqueous solution containing cir-dicyano-bis(2,2 -bipyridine)ruthenium(II) (photoactive donor) and potassium hexacyano-ferrate(III) (acceptor). These findings are ascribable to the electrostatic potential of the added polyelectrolytes. 

Entries where the oxidation state of a metal has been specified occur after all the entries for the unspecified oxidation state, and the same or similar entries may occur under both types of heading. Thus cyanide appears under Chromium complexes, Chromium(O) complexes, Chromium(I) complexes, etc. More specific entries, such as Chromium, hexacyano-, may also occur. Similar ligands may also occur in different entries. Thus a carboxylic acid-metal complex may occur under Carboxylic acid complexes, under entries for specific carboxylic acids, and under the specific metal. Coordination complexes may also be listed in the Cumulative Formula Index. 

Chromium, hexacyano-, 3, 703, 777 hexaamminecobaltate coordination isomerism, 1, 183 ligand field photochemistry, 1, 398 photochemistry excited states, 1, 398 production, 3, 704 Chromium, hexafluoro-, 3, 927 Chromium, hexabalo-, 3, 889 Chromium, hexaiodo-, 3, 766 Chromium, hexakis(dimethyl sulfoxide)-photoanation, 1, 399 Chromium, u-oxalatodi-reduction... 

Aldehydes 2,4-Dinitrophenyl- hydrazine Formation of colored hydrazones or osazones. It is possible to distinguish between saturated and unsaturated hydrazones using potassium hexacyano-ferrate(III) [5]. [3,4]... 

C20-0015. Explain why hexacyano complexes of metals in their +2 oxidation state are usually yellow, but the corresponding hexaaqua compounds are often blue or green. 

FIG. 1 (a) Cyclic voltammogram of the heterogeneous oxidation of ferrocene by the hexacyano-... 

See Copper(II) nitrate Ammonium hexacyanoferrate(II), or Potassium hexacyano-ferrate(II)... 

Figure 3 Schematic representation of hexacyano derivatives of examined molecules. The site of deprotonation is denoted by asterisks.

Caesium Chelation as copper hexacyano ferrate(II) on silica AAS - [864]... 

Caesium 137Cs adsorption on strong cation exchange resin ammonium hexacyano cobalt ferrate, dissolution in hydrochloric hydrofluoric acid /f counted for 137Cs lOpCi/1 [865]... 

In contrast to 51, hexacyano[3]radialene (50) proved difficult to obtain in pure form. Freshly prepared samples are bright-yellow, but mm brown on exposure to air and blue on contact with many solvents. Potassium bromide and sodium iodide reduce 50 to the radical anion and the dianion, respectively24. 

Hexacyano[3]radialene (50) is a very powerful electron acceptor according to both experiment23,24 35 and MNDO calculations of LUMO energy and adiabatic electron affinity25. The easy reduction to the stable species 50" and 502- by KBr and Nal, respectively, has already been mentioned. Similarly, the hexaester 51 is reduced to 512-by Lil24. Most [3]radialenes with two or three quinoid substituents are reduced in two subsequent, well-separated, reversible one-electron steps. As an exception, an apparent two-electron reduction occurs for 4620. The reduction potentials of some [3]radialenes of this type, as determined by cyclic voltammetry, are collected in Table 1. Due to the occurrence of the first reduction step at relatively high potential, all these radialenes... 

Copper ferrocyanide complex salts, which are occasionally used, are derived from copper-l-hexacyano-iron-2-acid HCu3[Fe(CN)6], Three equivalents of copper are required for each unit of ferrocyanide, which furnishes the following general pigment structure ... 

CF represents copper ferrocyanide (copper-l-hexacyano-iron-II-acid). 

Potassium hexacyano-ferrate(II). K4Fe(CN)6 Potassium hexacyano-ferrateflll), K, Fe(CN), Potassium thiocyanate, KCNS... 

The acidity constants for H4[Fe(C e] are pA i = 2.54, pA 2= 108, pAT3 = 2.65, pACj=4.19. Association constants have been published for alkali metal cations ion pairing with hexacyano-ferrate(II). ... 

The stabilization of Fe by 1,4,7-triathiacyclononane, ([9]-ane-S3, ttcn= (297), has permitted the preparation of the first authentic example of a Turnbull s Blue, i.e., an iron(II)-hexacyano-ferrate(lll) combination, in the form of [Fe(ttcn)2][Fe(CN)6] 2H20. This so-called Ukrainian Red, named in honor of the country of origin of several of the authors, is a valence-trapped (Robin and Day class compound. The redox potential for the [Fe(ttcn)2] " couple is... 

Conventional polyether polyol technology involves alkoxylation of the starters with PO and EO using an alkali metal hydroxide catalyst such as potassium hydroxide. The catalyst can be neutralized and the neutral salt can be left in the final polyol, or optionally the catalyst can be extracted by washing with water or by deposition on an ion exchange medium. In recent years, a new catalyst technology has become widely adopted within the polyols industry, using zinc hexacyano-cobaltate (double metal cyanide catalyst, or DMC), which runs at very high... 

This type of alkoxylation chemistry cannot be performed with conventional alkali metal hydroxide catalysts because the hydroxide will saponify the triglyceride ester groups under typical alkoxylation reaction conditions. Similar competitive hydrolysis occurs with alternative catalysts such as triflic acid or other Brpnsted acid/base catalysis. Efficient alkoxylation in the absence of significant side reactions requires a coordination catalyst such as the DMC catalyst zinc hexacyano-cobaltate. DMC catalysts have been under development for years [147-150], but have recently begun to gain more commercial implementation. The use of the DMC catalyst in combination with castor oil as an initiator has led to at least two lines of commercial products for the flexible foam market. Lupranol Balance 50 (BASF) and Multranol R-3524 and R-3525 (Bayer) are used for flexible slabstock foams and are produced by the direct alkoxylation of castor oil. 

Potassium ferricyanide Ferrate (3-), hexacyano-, tripotassium (8) Ferrate (3-), hexakis(cyano-C)-, tripotassium. (OC-6-11)- (9) (13746-66-2)... 

Dipotassium sodium ferricyanide [dipotassium sodium hexacyano-ferrate(3-)] K2Na[Fe(CN)6] [31940-93-9]... 

Hexacyano-dinickelate (1) ion, 4 141 Hexacyanofeirate ion, 3 24-25 Hexacyanometalate anions, 43 244—245 Hexadecacarbonylhexairidium, reaction with soft nucleophiles, 30 193 Hexadecacarbonylhexarhodium reactions of reduction, 30 176 with soft nucleophiles, 30 193... 

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