Uranyl complexes formamide

ESR spectra, 511 Uranium(VI) complexes dioxoneocupferron, 512 Uranium hexaalkoxides physical properties, 347 Uranyl complexes cupferron, 512 formamide, 491 glycolic acid, 472 hexafluoroacetylacetone, 373, 377 photochemistry, 385 rearrangement, 384 maleic acid conformation, 467 neutral 1,3-diketones, 402 poly ketones, 399 Urea... 

Polymerization of a dicarbonyl compound, a diamine, and a metal salt, is the most direct route to polymeric metal-Schiff bases (VII-12). One of the earliest uses of this reaction was as a colorimetric analytical method for metal ions (16). This reaction has been carried out in aqueous media, dimethyl-formamide (50), and mixed solvents incorporating benzene (50, 75). As with most chelate polymers, insolubility hampers obtention of high molecular weight. Molecular weights of 2000-11,000 were reported for the products obtained from some halogen-substituted bis(salicy aldehyde)-diamine-uranyl complexes (75). 

As has been discussed, ordinary formamides have a barrier of about 21 kcal/ mol, which is a little less than that required for the isolation of atropisomers at room temperature. This means that, at a temperature slightly lower than ambient, it may be possible to obtain stable rotamers. This possibility was first realized by Gutowsky, Jonas, and Siddall (40). They used a uranyl nitrate complex of N-benzyl-N-methylformamide (4) crystallized from dichloromethane. When the crystals were washed with ice water to strip off the uranyl nitrate, a mixture of E and Z forms (Z/E = 1.6) was obtained. Since the equilibrium mixture gives a Z/E value of 0.8, it was possible to perform a kinetic study of equilibration... 

Siddall and his co-workers (46) have examined the barriers to rotation of a series of 2,6-disubstituted anilides. Af-Ethyl-A/-(2,6-xylyl)formamide (9) was recrystallized as a uranyl nitrate complex, and one isomer, which at equilibrium was favored by a factor of 3 1, was enriched up to a 30 1 ratio. The kinetics of rotation were examined at 0 to 29°C. The Arrhenius activation energy was 26 3 kcal/mol and log A was 18.5 2.4 hr-1. Siddall and Gamer (47) were able to obtain an almost pure isomer (which also predominated at equilibrium 1.3 1 for the ethyl compound and 1.1 1 for the methyl compound) of Ar-alkyl- V-(2-methyl-4,6-dibromophenyl)-l-naphthamide (10). The half-lives of... 

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