Coordination chemistry, supported metal complexes

The smaller p -tert-butyl-calix [4] arenes have a rich coordination chemistry as well (65). Of these, however, only the upper-rim modified calixarenes seem to support metal complexes with confined binding sites (66), except in those cases where the lower-rim substituents form an appended cavity. Thus, Matt and coworkers have reported (67) a pocket-shaped calix[4]arene ligand L2 bearing two lower-rim [([Pg.410]

In the sixties of past century, a few patents issued to Bergbau Chemie [5,48,49] and to Mobil Oil [50-52], respectively described the use of CFPs as supports for catalytically active metal nanoclusters and as carriers for heterogenized metal complexes of catalytic relevance. For the latter catalysts the term hybrid phase catalysts later came into use [53,54], At that time coordination chemistry and organo-transition metal chemistry were in full development. Homogeneous transition metal catalysis was expected to grow in industrial relevance [54], but catalyst separation was generally a major problem for continuous processing. That is why the concept of hybrid catalysis became very popular in a short time [55]. 

The development, synthesis, and the coordination chemistry of novel metal complexes with deep binding cavities have been described. It was demonstrated that the doubly deprotona-ted forms of the macrocycles (LR)2 support the formation of... 

It is evident from the preceding discussion that the field of C02 coordination chemistry is still a new area, but enough work has been reported to allow the several different modes of C02 coordination to be identified. These include (1) binding to the metal center as a Lewis acid through carbon alone, (2) n-complexation involving one of the C=0 units, and (3) supported coordination in which an additional weak interaction stabilizes the bound C02. In all cases except for the irreversible reactions of C02 leading to bound carbonate, carboxylate, etc., the metal-C02 interaction is relatively weak and the C02 is easily liberated. 

The same coordination geometry was also inferred from the analysis of the lowest energy LMCT bands (see Ligand-to-Metal Charge Transfer) in the far-UV absorption spectra of Zu7- and Cd7-MT, and those of corresponding tetrahedral halide complexes (see Cadmium Inorganic Coordination Chemistry see Zinc Inorganic Coordination Chemistry) Further support came from... 

One of the consequences of the large increase in the number of structurally characterized compounds reported since the publication of Comprehensive Coordination Chemistry (CCC, 1987) is that some of the long-standing expectations for Group 1 and 2 chemistry need to be qualified. A conventional generalization holds that the coordination number (c.n.) of a complex should rise steadily with the size of the metal ion, and there is in fact abundant data to support this assumption for small monodentate ligands. For example, analysis of water-coordinated ions indicates that the most common c.n. for Mg +, and Ca + are four, six, and six to eight,... 

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