Stoichiometry, anion, lead

On the other hand, polytellurides only seem to oxidize metals to the +1 or +11 state. Reaction of equimolar amounts of Te4 with M(CO)6 results in disubstitution of CO forming a cu-complex (CO)4MTe4 (M = Cr (45), W (47)47). If an excess of metal carbonyl is used in the presence of poly-telluride anion, multinuclear products can be isolated and metal-metal bonds can also form, leading to clusters. Careful manipulation of reaction conditions and choice of the polychalcogenide anion used makes possible partial oxidation of the metal centers and cluster formation. The reaction of iron carbonyls with polytelluride anions can lead to a wide array of cluster compounds, the identities of which are controlled by the stoichiometries and compositions of the starting telluride anions. For instance, reaction of [Fe(CO)5] with Te2 leads to the formation of [Fe3(CO)9(ju.3-Te)]2 (48),48 whereas its reaction with increasing amounts... 

Bulk structures of oxides are best described by assuming that they are made up of positive metal ions (cations) and negative O ions (anions). Locally the major structural feature is that cations are surrounded by O ions and oxygen by cations, leading to a bulk structure that is largely determined by the stoichiometry. The ions are, in almost all oxides, larger than the metal cation. It does not exist in isolated form but is stabilized by the surrounding positive metal ions. 

The sample solution contains a fixed concentration of supporting electrolyte E" L and a varying concentration of primary salt M X . The ionophore I is confined in the membrane. Only the primary cation can be complexed with the ionophore I (given stoichiometry 1 1 stability constant The complex MI and the anionic site are the lipophilic species that are present only in the membrane phase. In this system, the electroneutrality condition at the membrane bulk leads to... 

The separation mechanism is based on stereoselective ion-pair formation of oppositely charged cationic selector and anionic solutes, which leads to a difference of net migration velocities of the both enantiomers in the electric field. Thus, the basic cinchona alkaloid derivative is added as chiral counterion to the BGE. Under the chosen acidic conditions of the BGE, the positively charged counterion associates with the acidic chiral analytes usually with 1 1 stoichiometry to form electrically neutral ion-pairs, which do not show self-electrophoretic mobility but... 

Theoretical calculations [43] based on first principles molecular dynamics discussed in Sect. 3.2.6 have suggested that Mg Al LDHs are most stable for n = 3 (i.e. x = 0.25) and indeed many minerals, including hydrotalcite itself, have this stoichiometry [4]. It has been reported that the synthesis of LDHs (with benzoate or terephthalate anions in the interlayers) from solutions containing Mg/Al = 2, leads to LDHs having the same composition when the synthesis is carried out at moderate temperatures but LDHs with Mg/Al = 3 (plus AlOOH) when the reaction is carried out under hydrothermal conditions [44]. It was proposed that the latter ratio represents the thermodynamically most favorable product. A similar observation has been reported [45] for solutions with Ni VPe = 2, where hydrothermal preparation led to segregation of an LDH with Ni VPe = 3 and Ni Fe 204. An attempt to synthesize a Co sAl LDH resulted in partial oxidation of the Co and formation of a Co o.yCo o.s LDH with complete migration of Al " from the layers to generate interlayer aluminum oxy-species [46]. 

The first evidence that post-transition elements, the metals especially, could be reduced to highly colored anions was published over 90 years ago by Joannls (O who discovered that sodium and lead or their alloys dissolve In liquid ammonia to yield an Intensely green-colored solute. A stoichiometry of 2.25 lead atoms per sodium ( ) for what was evidently an anion led Kraus ( ) to formulate this as Pbg ". Until the past decade the principal Information regarding this and many other species were the stoichiometries obtained by Zintl and coworkers from... 

Surprisingly, Screttas et al. (1996) have found that the reaction of the lithium naphthalene anion-radical with methanol in THF follows the 2 1 stoichiometry and leads to the CjqHj—C oHjo mixture in the 95 5 ratio. The authors proposed the following alternative ... 

The extraordinary feature of this process is that over a period of time, random CS planes can become ordered, with regularly spaced CS planes separated by slabs of an unperturbed parent matrix, leading to new phases. The overall stoichiometry of such a crystal depends on the spacing of the CS planes and the matrix slabs. At certain levels of anion deficiency this will produce the so-... 

Apart from the above-mentioned interest in m-octahedral species [M(bipy)2(anion)2] from the point of view of high-spin to low-spin transitions,72 this geometry is also of interest for the formation of reactive species, leading to, for example, dinuclear species with catalytic properties, such as the cobalt-peroxo compound shown in Figure 21. This compound is active in oxidative phenol coupling.132 With Cu the stoichiometry Cu(bipy)2X2 results in a variety of five-coordinate and distorted six-coordinate structures (see Figure 3).21... 

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