Halides extended solids

Redox Chemistry of the Group 5 Clusters Ligand Substitution Electronic and Molecular Structure Niobium Iodide Clusters NbJJ"-Materials Chemistry Derived from Soluble Metal Halide Clusters A. Higher Nuclearity Clusters Supported Cluster Materials Charge-Transfer Salt Complexes Extended Solids Chemically Modified Surfaces... 

As illustrated in the previous section, the metal-rich rare earth metal halides and their interstitial derivatives provide a vast collection of compounds that transcends the structural chemistry of both molecules and extended solids. On the one hand, these substances can be considered as connected or condensed clusters of the MgXi2-or MgXg-type, which may contain interstitial species. On the other hand, many of them can be derived from the structures of simple salts, e.g. NaCl or La20jS. 

Based on the similar crystal structure one might expect extended solid solutions between Cdl2-type dihalides and Bila-type trihalides, as well as between CdCl2-type and AlCla-type halides. This, however, appears not to be the case. The systems MgCl2—CrCla, FeCl2—CrCla and MnCl2—CrCla were found to be similar to eutectic-type systems [906]. Moreover, the different anion stacking is sufficient to prevent mixed-crystal formation between CrCla and FeCla [906]. 

For some typical ionic systems, sueh as binary systems of alkali halides or the binary systems of alkali metal salts of dibasic oxy-acids, the solid solubility is chiefly dependent on the ionic radii of cations and anions. By SVM computation, some criteria obtained are useful for the assessment of the relevant phase diagrams. For the binary systems of Me2X04-Me 2X04 (Me, Me = alkali metals, XO4 =S04, C1O4, etc.), most of them obey the criterion of formation of continuous or extended solid solution expressed as follows ... 

For binary systems of alkali halides with common cations or common anions, most of systems obey the criterion of formation of extended solid solution which can be expressed as follows ... 

In extending this direct method of synthesis, we next investigated the possibility of preparing similarly constituted halides from 2-deoxy-D-arabino-hexose (2-deoxy-D-glucose) (21). The hexose was subjected to a partial anomerization procedure described by Bergmann and co-workers (1). The solid material obtained by this procedure is a mixture of the anomeric forms of 2-deoxy-D-arabino-hexose low temperature p-nitro-benzoylation of the latter in pyridine resulted in a mixture of crystalline, anomeric tetrakis-p-nitrobenzoates in a ratio of approximately 1 1. They were readily separable by fractional recrystallization, and treatment of either with an excess of hydrogen bromide in dichloromethane, or with... 

No chalcogenide halides of zinc and cadmium are known. The phase diagrams of CdS-CdCl (7, 198, 210), CdSe-CdCl (220, 314), CdTe-CdClj 368), CdTe-CdBr2 (368), and CdTe-Cdl (323) are of a simple, eutectic type. The system CdS-CdCl shows a range of solubility of CdS in solid CdClj that extends to 5% of CdS at room temperature, and increases to a maximum of 12.5% of CdS at 500°C (7,210). 

The simple procedure for the carbonylation of allyl halides has been extended in the high yielding solid-liquid two-phase conversion of allyl phosphates into amides (60-80%) under the influence of a rhodium carbonyl cluster in the presence of primary or secondary amines (Scheme 8.8). A secondary product of the reaction is the allylamine, the concentration of which increases as the pressure of the carbon monoxide is reduced, such that it is the sole product (ca. 80%) in the absence of carbon monoxide [28],... 

Inorganic bases have been also employed in this system. When Butcher first used alkali carbonates [50], it was reported that, in DMF and at ambient temperature, the carbamation of primary and secondary aliphatic amines (or also arylamines) with alkyl halides under a C02 atmosphere (0.1 MPa) was effectively promoted by Cs2C03 [50, 51]. The Cs+ cations in the solvent used (DMF) did not form ion pairs with counterions, and favored the formation of naked carbamate anions that were more reactive at the O-ends with alkyl halides. Jung further found that the addition of tetrabutylammonium iodide (TBAI) to the system RR NH/ C02/RX/Cs2C03/DMF promoted the carbamation process with a higher yield and selectivity with respect to N-alkylation [51]. The process has been successfully extended to the synthesis of carbamate functionalities on solid phases. In this case, resin-bound carbamates are readily released from the resin by treatment with LiAlH4 in THF, yielding the respective N-methyl secondary amines [51]. 

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