CALCIUM HALIDE

Refluxing perfluorotoluene neat for 4 h with aluminum tnbromide produce p-bromoperfluorotoluene in 54% yield [<8/] Fluoropyndines can be transhalogen-ated at position 2 andfor 4 by heating in the presence of calcium halide in a nonhydroxylic solvent [82] (equation 62)... 

Highly Reactive Calcium for the Preparation of Organocalcium Reagents Preparation of 1-Adamantyl Calcium Halides and Their Addition to Ketones. 

Megagraft 1000, the calcium phosphate bioceramic, is synthesized by chemical reaction between calcium and phosphate ion sources (6-9). This synthesis is done by taking the mixture of a calcium and a phosphate source and heating it to a temperature below the starting melting point for an extended period of time. The calcium source can be from calcium phosphates, calcium hydroxide, calcium halides,... 

R. D. Rieke, T.-C. Wu, and L. 1. Rieke 147 HIGHLY REACTIVE CALCIUM FOR THE PREPARATION OF ORGANO-CALCIUM REAGENTS PREPARATION OF 1-ADAMANTYL CALCIUM HALIDES AND THEIR ADDITION TO KETONES 1 -(1 -ADAMANTYLJCYCLOHEXANOL... 

Highly reactive calcium can be readily prepared by the reduction of calcium halides in tetrahydrofuran solution with preformed lithium biphenylide under an argon atmosphere at room temperature.5 This colored calcium species seems to be reasonably soluble in THF. However, the reactive calcium complex prepared from preformed lithium naphthalenide was insoluble in THF solution and precipitated out of solution to give a highly reactive black solid. The exact nature of this black calcium complex has not been determined. Acid hydrolysis of the black material releases naphthalene as well as THF. Accordingly, the most likely structure of the black material is a Ca-naphthalene-THF complex similar in nature to the soluble magnesium-anthracene complex recently reported.6... 

Ammino-derivatives of Salts oe Subgroup A—Derivatives of Calcium Halides, Strontium Halides, and Barium Halides. 

The alkaline earths, particularly the lighter ones, have more definite water coordination, and a probable coordination number of 4. The heats of sublimation (Table I) of the magnesium salts are about 50 kcal/mole or higher, those for the calcium halides are over 60 kcal/mole, and for the heavier alkaline earths they run over 70 kcal/mole. For the beryllium halides other than the fluoride, however, the values are 30 to 33 kcal/mole. In... 

Halides. Calcium halides are made by reaction of elemental calcium and the halogens directly or more conveniently by the reaction of the corresponding hydrohalic acid and CaC03, CaO, or Ca(OH)2. 

A few calcium complexes having nitrogen ligands are known. Calcium halides form addition complexes with NH3 such as CaCl2wNH3 (n = 2,4,8) and CaBr2fiNH3 (n = 2,4,6,8). Hexaammine calcium [12133-31 -2], Ca(NH3)6, is formed by reaction of calcium metal and anhydrous NH3 (11) (see... 

Organometallic Chemistry. Only a few organocalcium compounds have been reported. Alkyl calcium halides have been prepared by reaction of the halides and calcium in tetrahydrofuran (17). 

Calcium halides and sodium metal react at elevated temperatures to form an equilibrium mixture1-5 of metals and halides ... 

CaSi2 reacts with ammonium halides to calcium halide and a silicon nitride with an Si N ratio of 3 l253- ... 

Reactions within a van der Waals (vdW) complex of calcium with hydrogen halides (HC1 and HBr) lead to electronically excited calcium halides. These reactions have been quite extensively studied in full collisions of excited calcium beams (Brinckmann et al. 1980 Brinckmann and Telle 1977 Rettner and Zare 1981, 1982 Telle and Brinckmann 1990). The electronic excitation of the calcium atom results in a strong chemiluminescence under collisional conditions. The efficiency of this chemiluminescence depends upon the electronic state and the fine structure component, and the final product state is influenced by the preparation conditions of the collision. In the reaction Ca(4s4p1P1) + HC1, the direction of the polarization of the P orbital with respect to the collision relative velocity (pK or pff) has an effect on the branching ratio to the products CaCl, A2n or B2X+ (Rettner and Zare 1981, 1982). 

Magnesium and calcium halides readily absorb water. The tendency to form hydrates, as well as the solubilities in water, decrease with increasing size, and Sr, Ba, and Ra halides are normally anhydrous. This is attributed to the fact that the hydration energies decrease more rapidly than the lattice energies with the increasing size of M2+. 

In addition to monomers of MX2 being present in the vapour state, there is evidence that magnesium and calcium halides form dimers. Electron diffraction data are consistent with the presence of <5% Ca2X4 for calcium halides, while data at 1065 K for magnesium bromide indicate that 12% of the gaseous sample is composed of Mg2Br4. 

Furthermore, both C-H iodinations and brominations can be achieved using the respective hahde salts in combination with oxidants [148]. Scheme 23.46 shows one example of this approach, in which calcium halides act as halide sources for C-H bond halogenations with Cu(02CCF3)j as stoichiometric oxidant [142]. 

This would work for the other calcium halides as well, but the product CaF2 is easier to handle under the reaction conditions (heated to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum [42]. 

How might the calcium halides be readily synthesized starting from the oxides Give a general equation for these reactions as part of your answer. 

Scheme 1 A generalized decomposition route for aryl calcium halide complexes. The acidic proton from the THE co-ligand is abstracted, yielding benzene, followed by liberation of ethene and formation of an aryl calcium ethenolate. The above mechanism is proposed based on observations from NMR experiments [71] and is in agreement with other estabhshed ether cleavage decomposition routes [99, 100]...

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