Polymers coordinative bonds

Chapter 2 Coordinative polymer bond in metal chelates... 

The porphyrins mth coordinative polymer bond are prepared under inert as follows ... 

The experimental evidence for the availability of the coordinative insufficiency of the transition metal ion in the propagation centers was obtained (175) in the study of the deactivation of the propagation centers by coordination inhibitors. On the introduction of such inhibitors as phosphine and carbon monoxide into the polymerization medium, the reaction stops, but the metal-polymer bond is retained. It shows that in this case the interaction of the inhibitor with the propagation center follows the scheme ... 

Olefin polymerization by catalysts based on transition metal halogenides is usually designated as coordinated anionic, after Natta (194). It is believed that the active metal-carbon bond in Ziegler-Natta catalysts is polarized following the type M+ - C. The polarization of the active metal-carbon bond should influence the route of its decomposition by some compounds ( polar-type inhibitors), e.g. by alcohols. When studying polymerization by Ziegler-Natta catalysts tritiated alcohols were used in many works to determine the number of metal-polymer bonds. However, as it was noted above (see Section IV), in two-component systems the polarization of the active bond cannot be judged by the results of the treatment of the system by alcohol, as the radioactivity of the polymer thus obtained results mainly from the decomposition of the aluminum-polymer bonds. 

Other Fe(II) btr coordination polymers with monovalent anions have been obtained [9, 67, 68]. [Fe(btr)3](CF3S03)2 is a HS compound. The stabilisation of the HS state is presumably due to the large size of the trifluo-romethanesulfonate anion, which could increase the size of the cavities and, by mechanical influence, the Fe-N bond lengths, precluding the thermal spin crossover [9]. X-ray investigations should clarify this behaviour. Iron(II) btr compounds with BF4 and PF6 anions exhibit incomplete TSCO, with Ti/2 150 K and 170 K, respectively. Interestingly, the 3D architecture of [Fe(btr)3](Cl04)2 is not retained in these derivatives as water molecules are detected in the coordination sphere of some Fe species [68]. 

The network structures to be discussed will all involved hydrogen bonding as the supramolecular synthon. It should be noted however that other interactions such as coordinate bonds and host-guest interactions may also organise host molecules into network structures. Coordination polymers constructed from molecular hosts may involve functionalised calixarenes [8-11], cyclotriveratrylene [12], or cucurbituril [13]. Calixarenes have also been used to build up network structures via host-guest interactions [14,15]. It is also notable that volatile species may be trapped within the solid state lattice of calix[4] arene with a structure entirely composed of van der Waals interactions [16]. 

In this report, both the structure-based and source-based nomenclature rules are extended to regular double-strand (ladder and spiro) organic polymers. Biopolymers, however, such as DNA are not considered here. Rules for quasi-single-strand coordination polymers, resembling spiro polymers yet not covalently bonded, are not included. 

Bailar listed a number of principles that can be considered in designing coordination polymers as follows (1) Little flexibility is imparted by the metal ion or within its immediate environment thus, flexibility must arise from the organic moiety. Flexibility increases as the covalent nature of metal-ligand bond increases. (2) Metal ions only stabilize ligands in their immediate vicinity thus, the chelates should be strong and close to the metal ions. (3) Thermal, oxidative, and hydrolytic stabilities are not directly related polymers must be designed specifically for the properties desired. (4) Metal-ligand bonds have sufficient ionic character... 

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