The reaction of MoCl62" or MoCl6" with Mo(CO)4Cl3~inCH2Cl2 results in the formation of Mo2Cl,3" and MoCl92", respectively. The temperature dependence of the magnetic moment of the latter is shown to be hi accord with the thermal equilibrium 5 = */2 4* S = 3/2, while its infrared spectrum can be readily assigned assuming a bioctahedral, D3h structure. It is easily reduced to Mo2C193_. The reaction of Mo2Cl92' with Mo(CO)4Cl3" leads to Mo3C1123" whose trinuclear structure was verified from conductivity measurements. Both the electronic and the infrared spectra are in accord with a linear, trioctahedral, face-shared structure (unlike Re3Cl123"). Magnetic moments in solution are in qualitative agreement with the thermal equilibrium 5 = '/2 & S = 3/2.
A study of the distribution coefficients (K0) of the alkali metals between solutions containing HCI or HN03-crown ether-80 % (v/v) methanol and Aminex A7 resin was performed. The KD's of Na between solution and resin phase were studied as a function of the methanol concentration, acidity, and crown ether concentration. Measured KD's were compared to KD's calculated from the Independently measured partition coefficients and formation constants of the sodium crown ether complexes. Predictive modeling equations for the KD's of the alkali metals In solutions containing either the A or B isomers of dicyclohexyl-18-crown-6 (DCH) were derived. These equations were used to devise separations of the alkali metals by high efficiency Ion exchange chromatography. Finally, the chromatographic separation of the sodium isotopes, 22Na and 24Na, was investigated. Isotopic exchange constants for 18-crown-6 and DCH were measured as a function of temperature.Within the past decade many macrocyclic polyethers, commonly called crown ethers, have been synthesized. These compounds exhibit the unique property of forming not only very stable complexes with the alkali and alkaline earth metals but also of showing a large selectivity for these ions. Although many studies have been devoted to their synthesis, structural characterization, and general complexating properties (1-4), the use of these reagents for analytical separations has been lacking. This report describes a high performance liquid chromatography (HPLC) system which uses the ligating properties of the crown ethers to affect separations of the alkali metals. A 9-µ diameter particle of Dowex 50W-X8 cation exchange resin (trade name, Aminex A7) is used as support, and the mobile phase is HCI + crown ether in 80% methanol.The crown ethers studied were the cis-syn-cis and cisanti-cis isomers of dicyclohexyl-18-crown-6 (DCH(A) and DCH(B), respectively) and 18-crown-6. These ethers were chosen because: (1) They are all commercially available at modest cost; (2) Methods of purification have been published and are relatively simple; (3) The thermodynamic properties of complexation have been well characterized for the alkali metals in several solvents (4-6).
EXPERIMENTALReagents and Radioisotopes. All solutions were prepared using ultrapure water obtained from a MÜ1Í-Q2 system water purifier (Millipore Corp., Bedford, Mass.), methanol distilled in glass from Burdick and Jackson, and Ultrex grade acids from J.T. Baker Chemical Co. Crown ethers were obtained from either PCR, Inc. (18-crown-6), or Aldrich Chemical Company, Inc. (dicyclohexano-18-crown-6). The isomers of the latter ether were obtained as described in Ref. 7.The radionuclides, 22Na, 134Cs, and ^^Rb, were obtained from laboratory stocks and purified by cation exchange chromatography. The 24Na was prepared in the ANL cyclotron. The tritium labeled dicyclohexyl-18-crown-6 (3H-DCH) was prepared by New England Nuclear Corp. One mCi of the tritiated crown was diluted with 1 g of inactive crown before separation into the A and B is...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.