Calcium complexes coordination compounds

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). 

Site symmetry symbols, I, 128 Six-coordinate compounds stereochemistry, 1, 49-69 Six-membered rings metal complexes, 2, 79 Skeletal muscle sarcoplasmic reticulum calcium pump, 6, 565 Slags... 

Elements with very low electronegativity (alkali metals, alkaline earth metals, such as Na, Ca and Mg) and elements with high electronegativity (halogens such as Cl and I) occur mainly as free ions in biological materials, and are preferably involved in electrostatic interactions. However, even these elements can form less soluble compounds (calcium oxalate), covalent compounds (hormones thyroxine and triiodothyronine are iodinated aromatic amino acids, see Section 2.2.1.2.5) or complex compounds (chlorides as Hgands and some metal ions as central atoms). A ligand is an entity (atom, ion or molecule), which can act as an electron pair acceptor to create a coordinate covalent bond with the central ion. Cd and Hg also tend to form covalent compounds. 

Treatment of the amine 173 (LBu H) in a 2 1 ratio with M[N(SiMe3)2]2(THF)2 (M = Ca, Sr, Ba) in toluene at ambient temperatures affords ( 5-LBut)2M 174 in >93% yields.395 All three compounds possess bent-sandwich structures with -coordinated /3-diketiminato ligands. Similar treatment of the Pr analog of 173 (i.e., LPr H) yields the corresponding calcium and strontium complexes (r 2-LPr )2Ca 175 and (r/s-LPr )2Sr, respectively, in high yield. The reaction of Ba[N(SiMe3)2]2(THF)2 with LPr H yield the -symmetric dinuclear complex 176 (Figure 90). The... 

A metal-nucleotide complex that exhibits low rates of ligand exchange as a result of substituting higher oxidation state metal ions with ionic radii nearly equal to the naturally bound metal ion. Such compounds can be prepared with chromium(III), cobalt(III), and rhodi-um(III) in place of magnesium or calcium ion. Because these exchange-inert complexes can be resolved into their various optically active isomers, they have proven to be powerful mechanistic probes, particularly for kinases, NTPases, and nucleotidyl transferases. In the case of Cr(III) coordination complexes with the two phosphates of ATP or ADP, the second phosphate becomes chiral, and the screw sense must be specified to describe the three-dimensional configuration of atoms. 

Recovery of the resolved alcohols was achieved by extraction or distillation. In special cases ligand exchange (similar to the before mentioned workup procedures of the calcium compounds) was used to liberate the previously complexed alcohol enantiomer. Results of the optical resolutions made by DBTAZn are summarized in Table 3 where the overall numbers of the coordinated auxiliary ligands (nAi and mA2) are also given on the basis of X-ray analysis data. [25]... 

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