Macroligands complexes

Table 3-1. Stability constants and thermodynamic data for the M -macroligand complexes.

Complex formation takes place in an organic solvent or in a water/monomer mixture by reaction of the macroligand with a metal compound (e.g. a Cu(I)-ha-lide). It is supposed that the conditions in the reaction mixture are comparable to those in conventional emulsion polymerization, where monomer droplets stabilized by surfactant molecules coexist with monomer swollen micelles [64]. Reaction sites are presumably the hydrophobic core of the micelles and the monomer droplets as well. Initial results of the micellar-catalyzed ATRP of methyl methacry-... 

It seems worth pointing out, that 137 and human semm albumin contain no pendant phosphines and the donor atoms in the complexes formed with rhodium can be only O (137) or O, N and perhaps S (HSA), which are not the most suitable for stabilizing low oxidation state metal ions. Still these macroligands gave active and stable catalysts with rhodium, which shows that perhaps in the high local concentration provided by the polymer even these hard donor atoms are able to save the metal ion against hydrolysis or other deterioration. 

P-Cyclodextrin was modified by attaching 2-(diphenylphosphinoethyl)-thio- (127) and 2-bis(diphenylphosphinoethyl)amino- (126) moieties at the C-6 position [8-11]. The resulting macroligands were reacted with [ RhCl(NBD) 2] to provide the corresponding cationic rhodium-bisphosphine complexes. These catalysts showed pronounced selectivity due to complexation of the substrate by the CD unit adjacent to the catalyticaUy active metal center. For example, in competitive hydrogenation of similarly substituted terminal olefins (Scheme 10.4), 4-phenyl-but-l-ene was... 

Macromolecular metal complexes can be classified into three main categories, taking into consideration the manner of binding of a metal compound to suitable macroligands [33] (Fig. 1). Type 1 metal complexes are those with the metal ion or metal chelate at a macromolecular chain, network, or surface. One possible approach to synthesize such polymers is using the polymerization of vinyl-substituted metal complexes. 

The assessment of the chelating ability of macroligands and applicability of such systems requires the data on the quantitative evaluation of the chelation processes such a stability constants and formation function. Contemporary methods are largely based on the composition of the products formed. The major methods of analyzing the quantitative parameters of MX chelation use predominantly the same techniques that are applied to the description of complexing reactions with participation of monofunctional macroligands [5, 7b, 13a]. 

The macroligand permits us to trace the stagewise mechanism of PCMU formation, to isolate the intermediate and stabilize (in the case of unstable low-molecular weight analogs) complexes. 

Interestedly that this metallopolymer is distinguished by strong fluorescence which is proportional to metal content as distinct from complexes produced by the interaction of EuC13 with macroligands containing 2-carboxybenzoyl (14) or 2-carboxynaphthoyl (15) groups (Fig. 7) [67]. A similar method was used to copolymerize MMA and MCM of Eu(III) with l-(vinylphenyl)-3-phenyl-l,3-propandione [89]. 

As shown in Eq. 1, the support acts as a macroligand for the metal. Depending on the number of bonds between the metal and the support (y = 1, 2 or 3), the metal can be considered as singly, doubly, or triply bonded to the support. The value of y may vary with the reactivity, concentration, and nature of both the OH and the coordination metal complex, and also with the reaction temperature. 

The results of dimerization of ethylene in the presence of the obtained nickel, titanium and zirconium complexes with different macroligands and OAC are given in Table 1. The temperature in all the experiments was 313 K pressure 0,2 MPa OAC/Ni molar ratio of 10 and OAC/Ti or Zr of 4. 

It can be also seen from Table 1 that nickel complexes with PMAA macroligands demonstrate 86% selectivity with respect to 1-butene, whereas in case of homogeneous nickel complexes, as it was already mentioned, the selectivity does not exceed 3 %. 

Recently, it has been shown that coupling the chiral ligand PPM with a water-soluble poly(acrylic acid) gave a macroligand 9, the rhodium complex of which allowed the reduction of amino acid precursors in water or water/ethyl acetate as the solvents with enantioselectivity up to 56 and 74%, respectively [41]. 

The last term of the equation involves the additional entropy caused by different structures of the chain at the same composition. Minimizing the equation is carried out for chains of infinite length taking material balance equations into consideration. In general, if there are q metal ions on the polymer chain containing m active centers, it is necessary to consider the combinatorial analysis of complexes formed having different structures, i.e. the number of combinations (/) of q molecules on m centers of the macroligand t =... 

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