Group 2 metal chlorides

Both SeCLj and TeCl4 are readily hydrolysed by water, but with group 1 metal chlorides in the presence of concentrated HCl, yeUow complexes such as K2[SeCl6] and K2[TeCl6] are formed. Reaction 16.80 is an alternative route to [TeClg] , while [SeCl ] is formed when SeCLj is dissolved in molten SbCl3 (eq. 16.81). 

To obtain vinylsilanes from alkynes, transition metal complexes of Group VIII combined with a main group metal chloride are particularly effective." In the presence of a heterogeneous catalyst like Pd/y-alumina, Rh/carbon and polymer bound Pt, trichlorosilane gives trichlorovinylsilane with atmospheric pressure of acetylene." Platinum supported on sulfur-containing silica gel is a practical catalyst for 1,2-dihydrosilylation, as exemplified in equation (10). ... 

Anion Retention. Transition metal chlorides are often favored as catalyst precursors because of their ready availability, high solubility, and their ease of reduction. However, residual chloride anions (from incomplete catalyst reduction) can have a very marked effect on the properties of the catalysts. While the platinum group metal chlorides are, from a thermodynamic standpoint, very easy to reduce (Pt > Ru > Ir > Rh), residual chloride ions on the metal surface can be tenaciously bonded. The severity necessary to remove all the surface chloride reflects the surface energy of the metal (Ru, Mo, Ir > Rh > Pt > Pd). In the case of ruthenium, although bulk reduction apparently occurs at around 470 K, extended reduction above 700 K can be necessary to remove all chloride anions. The presence... 

Treatment of impure gold is largely via the Miller process (30) in which chlorine is bubbled through the molten metal and converts the base metals to chlorides, which volatilise. Silver is converted to the chloride, which is molten and can be poured. The remaining gold is less pure (99.6%) than that produced by the WohlwiU process and may require additional treatment such as electrolysis. If platinum-group metals (qv) are present, the chlorine process is unsuitable. 

Platinum-group metals (qv) form complexes with chelating polymers with various 8-mercaptoquinoline [491-33-8] derivatives (83) (see Chelating agents). Hydroxy-substituted quinolines have been incorporated in phenol—formaldehyde resins (84). Stannic chloride catalyzes the condensation of bis(chloromethyl)benzene with quinoline (85). 

Dirubidium phthalocyanine (PcRb2) and dicesium phthalocyanine (PcCs2) can be prepared by chemical-vapor deposition of benzene-1,2,4,5-tctracarbonitrile and the metal chloride.135 In the solid phase, additional rubidium atoms are complexed between peripheral cyano groups. 

Colour - A striking feature of transition-metal compounds is their colour. Whether it is the pale blue or pink hues of copper(ii) sulfate and cobalt(ii) chloride, or the intense purple of potassium permanganate, these colours tend to be associated most commonly with transition-metal compounds. It is rare for compounds of main group metals to be highly coloured. 

The graphite-metal halides constitute the most populous group of intercalation compounds. Most of the investigative efforts have been directed towards the metal chlorides, particularly FeCls, whereas considerably less is known about the metal bromides S21). Compounds... 

Scheme 23 Synthesis of group 10 metal polysulfido complexes by the reaction of the metal chlorides with polysuhide dianions...

To optimize the alkylation conditions, ferrocene was reacted with allyldimethyl-chlorosilane (2) in the presence of various Lewis acids such as aluminum halides and Group lO metal chlorides. Saturated hydrocarbons and polychloromethanes such as hexane and methylene chloride or chloroform were used as solvents because of the stability of the compounds in the Lewis acid catalyzed Friedel-Crafts reactions. The results obtained from various reaction conditions are summarized in Table IV. 

As shown in Table IV, the highest catalytic activity of metal halides used as Lewis acid for the alkylation reaction of ferrocene with 2 was observed in methylene chloride solvent. Among Lewis acids such as aluminum chloride, aluminum bromide, and Group 4 transition metal chlorides (TiCl4, ZrCU, HfCU), catalytic efficiency for the alkylation decrea.ses in the following order hafnium chloride > zirconium chloride > aluminum chloride > aluminum bromide. Titanium chloride... 

All metals, except those belonging to the platinum group, form chlorides and the free energy change for the reaction (referred to as reaction (1))... 

Alam, M. S. Inoue, K. Extraction of rhodium from other platinum group metals with Kelex 100 from chloride media containing tin. Hydrometallurgy 1997, 46, 373-382. 

Vest, P. Schuster, M. Konig, K. H. Influence of tin(II) chloride on the solvent-extraction of platinum group metals with N,N-di-normal-hexyl-N -benzoylthiourea. Fresenius J. Anal. Chem. 1991, 339, 142-144. 

Table 1 Costs of representative group 4-7 metal chlorides...

That this is possible is demonstrated by the formation of [Ta(CH2CMe3)3(CHCMe3)] (Ref.62 ) and [Cp2Ta(CH2)Me] Ref.63. A quantitative indication of the extent to which initial decomposition may be favoured can be obtained from the stepwise dissociation enthalpies of some metal chlorides (Table 8). These show that the difference, A, between >] and D increases from group four to group six (i.e. with the value of ) and that A decreases with increasing atomic number within a group. 

Mixed metal ruthenium/group 9 clusters also show rich chemistry. Synthetically, such clusters are generally synthesized by the addition of a metal chloride to an anionic boridocluster in a cluster expansion reaction. For example, [Ru3(CO)9BH4]- undergoes cluster expansion with [Ru(776-arene)Cl2]2 (arene = CgHsMe, MeCgH4-... 

The sol-gel methodology can also be applied to non-hydrolytic processes. The preparation of methylsilsesqui-oxane-titanium oxide hybrid by the etherolysis-condensation of a mixture of methyltrichlorosilane and metal chloride,353 354 and by the condensation of preformed poly(methylsilsesquioxane) carrying Si-OH and Si-OCHj groups with titanium(iv) -butoxide,355 has been reported. 

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