Table salt, square crystals

In this reaction, the crystal stmcture of each compound has been noted in the square brackets. An interesting feature of the compounds on the right-hand side is that neither of them is in the crystal structure that is the stable structure at ambient conditions. MgO, for example, prefers the NaCl structure at ambient conditions (i.e., the same crystal structure as everyday table salt). The behavior of Si02 is similar but more complicated this compound goes through several intermediate structures between ambient conditions and the conditions relevant for MgSi03 dissociation. These transformations in the structures of MgO and Si02 allow an important connection to be made between DFT calculations and experiments since these transformations occur at conditions that can be directly probed in laboratory experiments. The transition pressures... 

Bis(dialkyldithiophosphinato)nickel(II) complexes were prepared by the direct synthesis of an alkali metal or ammonium salt of the dithiophosphinic acid and a nickel salt in aqueous solution.2039,2061"2063 Ni(S2AsR2)2 and Ni(Se2PR2)2 complexes were prepared in a similar way.2064"2066 All of these complexes are square planar like their dithiophosphate analogues. X-Ray crystal structures of the complexes Ni(S2PR2)2, with R = Me,2067 Et, Ph,1983 R2 = Me/ Et 2°w r2 = Me/2-thienyl,2069 and Ni(Se2PPh2)21984 have been reported (Table 90). 

When the salt of PMAA is formed the rigidity of polymer chain is increased a little that leads to little increase of values of mean-square length of monomer unit and distance between polymer chain ends. The result obtained under addition to polymer salt solvent in methanol (40 vol. % of water, at large content of water the solution is not vitrificated, but is crystallized) represents special interest at that the macromolecule in solid state keeps conformation of Gauss ball (Figure 2), however, as we should expect, rigidity (parameter a) and sizes of ball are increased (Table 1). 

Table 5.2. Coordination numbers, C, Madelung constants, M, and calculated bond distance ratios, R R, for gaseous, monomeric alkali metal halides MX, gaseous square dimers M2X2, for cubic tetramers M4X4 and for MX crystals with rock-salt structures.

Treatment of K2[PdCl4] with 14S4 in MeCN/CH2Cl2 affords [Pd(14S4)] + as yellow crystals after recrystallization from water and metathesis to the hexa-fluorophosphate salt (Eqs. 32a, b). X-ray diffraction confirms the expected square-planar geometry of a cation with syn stereochemistry (Fig. 13 Table 1) [129, 136]. 

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