Aluminum complexes cyanides

Beryllium, calcium, boron, and aluminum act in a similar manner. Malonic acid is made from monochloroacetic acid by reaction with potassium cyanide followed by hydrolysis. The acid and the intermediate cyanoacetic acid are used for the synthesis of polymethine dyes, synthetic caffeine, and for the manufacture of diethyl malonate, which is used in the synthesis of barbiturates. Most metals dissolve in aqueous potassium cyanide solutions in the presence of oxygen to form complex cyanides (see Coordination compounds). 

Cyanadons. Aluminum complexes of BINOLs (1) that are armed at C-3 and C-3 with diarylphosphine oxide groups possess both Lewis acid and base centers. Asymmetric cyanation of aldehydes and mines with MeaSiCN, and of quinolines and isoquinolines in a manner analogous to the Reissert reaction is successful (ee 70-90%). The asymmetric Strecker synthesis is applicable to conjugated aldimines and the higher reactivity of Me SiCN than HCN in the presence of 10 mol% of PhOH enables its use in catalytic amount while supplying stoichiometric HCN as the cyanide source. 

Ooi and Maruoka found that aluminum alkoxide (83) prepared from aluminum complex (82) and tertiary propargyl alcohol reacts with highly electrophilic aldehydes, such as chloral and pentafluorobenzaldehyde, to give alkynyl transfer products in good yield (Scheme 6.65) [84]. Bisphenol structure of ligands on aluminum center is the most important feature to obtain the alkynylated products, and thus, in reactions with (84) or (85) instead of (83) dramatical decrease in the yield of alkynyl product was observed. Same group also reported that cyanide transfer reaction with acetone cyanohydrin as a cyanide donor catalyzed by complex (82) [84]. 

Electroplating. Aluminum can be electroplated by the electrolytic reduction of cryoHte, which is trisodium aluminum hexafluoride [13775-53-6] Na AlE, containing alumina. Brass (see COPPERALLOYS) can be electroplated from aqueous cyanide solutions which contain cyano complexes of zinc(II) and copper(I). The soft CN stabilizes the copper as copper(I) and the two cyano complexes have comparable potentials. Without CN the potentials of aqueous zinc(II) and copper(I), as weU as those of zinc(II) and copper(II), are over one volt apart thus only the copper plates out. Careful control of concentration and pH also enables brass to be deposited from solutions of citrate and tartrate. The noble metals are often plated from solutions in which coordination compounds help provide fine, even deposits (see Electroplating). 

The metal may he analyzed hy atomic absorption or emission spectrophotometry (at trace levels). Other techniques include X-ray diffraction, neutron activation analysis, and various colorimetric methods. Aluminum digested with nitric acid reacts with pyrocatechol violet or Eriochrome cyanide R dye to form a colored complex, the absorbance of which may be measured by a spectrophotometer at 535 nm. 

The problem of the stability of the complexes of the transition metals was for many years a puzzling one. Why is the cyanide group so facile in the formation of complexes with these elements, whereas the carbon atom in other groups, such as the methyl group, does not form bonds with them Why do the transition metals and not other metals (beryllium, aluminum, etc.) form cyanide complexes In the ferro-... 

In the presence of aluminum chloride, which presumably lowers the energy of the LUMO of the heterodiene by Lewis acid complexation, electron-rich alkenes give dihydropyrans on reaction with acyl cyanides at room temperature (82AG(E)859). Unsaturated esters further extend the range of diene components of value in these Diels-Alder reactions with inverse electron demand (82TL603). 

Virtually all chelate complexes of the type M(Ox)m derived from the cation Mm+ are extractable into chloroform and, being coloured, form the basis of spectrophotometric determinations. The extractions can be made more selective by controlling the pH (cf. Section 10.2.2.1) and/or by using suitable masking agents. Thus extraction of the yellow aluminum trisoxinate can be made almost specific at pH 8.5—9.0 if EDTA, cyanide ions and sulfite ions (to reduce FeI I to Fe11) are present. Since the range for extraction of individual metal oxinates extends from pH 1.6 to 14, separation of individual species is facilitated.52 59... 

Discovery. These catalysts were discovered during a study of the use of transition metal cyanides in combination with metal alkyl and hydride reducing agents in polymerizations. The combination of nickel cyanide and lithium aluminum hydride complexed very strongly with tetrahydrofuran. A similar complexing action occurred with propylene oxide and nickel hexacyanoferrate(II)-lithium aluminum hydride. This led to speculation as to the role of the double-metal cyanide itself. 

Formation of Complex Ions.—In certain cases the solubility of a sparingly soluble salt is greatly increased, instead of being decreased, by the addition of a common ion a familiar illustration of this behavior is provided by the high solubility of silver cyanide in a solution of cyanide ions. Similarly, mercuric iodide is soluble in the presence of excess of iodide ions and aluminum hydroxide dissolves in solutions of alkali hydroxides. In cases of this kind it is readily shown by transference measurements that the silver, mercury or other cation is actually present in the solution in the form of a complex ion. The solubility of a sparingly soluble salt can be increased by the addition of any substance, whether it... 

Dichloro(l, 3-propanediyl)platinum and its bis(pyridine) derivative have been studied by a number of authors. Dichloro(l,3-propanediyl)platinum, and the corresponding substituted 1,3-propanediyl platinum compounds release the parent cyclopropane on treatment with potassium cyanide, potassium iodide, a tertiary phosphine, carbon monoxide, and other ligands.2,6 Reduction by means of hydrogen or lithium aluminum hydride yields chiefly isomeric substituted propanes. Dichlorobis(pyridine)(l,3-propanediyl)platinum in refluxing benzene yields a pyridinium ylid complex, - (CH3CH2CHNC5Hs)-PtpyCla. 

The only known metal catalyst for the asymmetric catalytic Strecker reaction is the aluminum salen catalyst 465 (Sch. 65) recently reported by Sigman and Jacobsen [97]. They prepared 11 different chiral salen complexes from different transition and main group metals and screened these complexes for the addition of trimethylsilyl cyanide to imine 460 at room temperature. The aluminum catalyst 465 was optimum in terms both of asymmetric induction and rate. This constitutes the first aluminum salen complex successfully developed for an asymmetric catalytic reaction. 

Diverse chemicals have been reported to affect measured endpoints of fish thyroidal status. These chemicals include aromatic hydrocarbons, planar halogenated aromatic hydrocarbons (dioxans, furans, coplanar PCBs), organochlorine, organophosphorus and carbamate pesticides, chlorinated paraffins, cyanide compounds, methyl bromide, phenol, ammonia, metals (aluminum, arsenic, cadmium, lead and mercury), low pH conditions, environmental steroids and a variety of pharmaceutical agents. For the following reasons their modes of action appear complex and are poorly understood16. 

In contrast to the low yield when hydrogen chloride is employed, an 88% yield of 2,4,6-triphenyl- 1,3,5-triazine (7) is obtained when chlorosulfonic acid is used as catalyst in a molecular ratio of 3 1 (CiSOjH/PhCN) at 0-5 C C and a reaction time of 12 to 24 hours.174 Trifluo-romethanesulfonic acid as a catalyst and solvent trimerizes benzonitrile at 91 °C in a yield of 66%.175 Lewis acids alone, such as aluminum, zinc, iron or titanium chlorides, phosphorus pentachloride, and boron trifluoride, have a considerably lower catalytic activity than the corresponding mixtures of Lewis acid with various promotors, such as mineral acids, organic acids and water. These differences are attributed to a change in the structure of the active complexes with the aryl cyanides. 

Enantiopure sulfinimines (thiooxime-S-oxides) 44 have been reported to facilitate the asymmetric Strecker reaction.28 Davis found that typical cyanide sources, such as potassium cyanide and TMSCN, did not possess sufficient reactivity for addition to the sulfinimines. Product 46, however, could be obtained using the more Lewis acidic Et2AlCN. Not only did the coordination of the aluminum to the oxygen of the sulfinimine activate the imine toward nucleophilic addition, this complexation also facilitated the delivery of the nitrile (see 45), These results triggered numerous modifications and variations that have enhanced this approach to chiral a-amino acids. 

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