Ruthenium complex polymers synthesis

Subsequent to isolation of the polymer, the metallization could be conducted in a similar manner as that of the complexes reported elsewhere for DCH-Ru complexes (27-28). The ruthenium complex polymers, shown in Figure 2, thus made would be expected to exhibit similar electrochromic properties as the dinuclear ruthenium complexes while possessing the film forming characteristics of the parent polymer. We report herein the synthesis and characterization of these polymers. 

Fig. 11. Gibson and coworkers synthesis of a polymer displaying the nucleobase thymine using ROMP initiated by Grubbs ruthenium complex... 

For the synthesis of carbohydrate-substituted block copolymers, it might be expected that the addition of acid to the polymerization reactions would result in a rate increase. Indeed, the ROMP of saccharide-modified monomers, when conducted in the presence of para-toluene sulfonic acid under emulsion conditions, successfully yielded block copolymers [52]. A key to the success of these reactions was the isolation of the initiated species, which resulted in its separation from the dissociated phosphine. The initiated ruthenium complex was isolated by starting the polymerization in acidic organic solution, from which the reactive species precipitated. The solvent was removed, and the reactive species was washed with additional degassed solvent. The polymerization was completed under emulsion conditions (in water and DTAB), and additional blocks were generated by the sequential addition of the different monomers. This method of polymerization was successful for both the mannose/galactose polymer and for the mannose polymer with the intervening diol sequence (Fig. 16A,B). 

Ruthenium is not an effective catalyst in many catalytic reactions however, it is becoming one of the most novel and promising metals with respect to organic synthesis. The recent discovery of C-H bond activation reactions [38] and alkene metathesis reactions [54] catalyzed by ruthenium complexes has had a significant impact on organic chemistry as well as other chemically related fields, such as natural product synthesis, polymer science, and material sciences. Similarly, carbonylation reactions catalyzed by ruthenium complexes have also been extensively developed. Compared with other transition-metal-catalyzed carbonylation reactions, ruthenium complexes are known to catalyze a few carbonylation reactions, such as hydroformylation or the reductive carbonylation of nitro compounds. In the last 10 years, a number of new carbonylation reactions have been discovered, as described in this chapter. We ex-... 

Arene ruthenium complexes are used frequently in metal-mediated organic synthesis for a wide range of reactions.5 For the purposes of our studies we have focused attention mainly on enol formate synthesis as a representative reaction for comparing the activity of 2 with its non-supported analogue 5. As with the supported cobalt complex, we find that attachment of 5 to a polymer support has little effect in its catalytic activity with a range of enol formates being prepared in high yield. 

Here, we shall focus on ruthenium-catalyzed nucleophilic additions to alkynes. These additions have the potential to give a direct access to unsaturated functional molecules - the key intermediates for fine chemicals and also the monomers for polymer synthesis and molecular multifunctional materials. Ruthenium-catalyzed nucleophilic additions to alkynes are possible via three different basic activation pathways (Scheme 8.1). For some time, Lewis acid activation type (i), leading to Mar-kovnikov addition, was the main possible addition until the first anfi-Markovnikov catalytic addition was pointed out for the first time in 1986 [6, 7]. This regioselectiv-ity was then explained by the formation of a ruthenium vinylidene species with an electron-deficient Ru=C carbon site (ii). Although currently this methodology is the most often employed, nucleophilic additions involving ruthenium allenylidene species also take place (iii). These complexes allow multiple synthetic possibilities as their cumulenic backbone offers two electrophilic sites (hi). 

These studies, and their long history, have provided numerous aspects of organic and polymer chemistry in which a variety of transition metal complexes and salts actually behave as efficient catalysts. In particular, certain ruthenium complexes, of which typical examples are illustrated in Figure 13.1, sometimes show distinctly different activity and/or selectivity from those available with other catalysts. The purpose of this chapter is to describe special features of ruthenium catalysts in these radical reactions, and to highlight the importance of ruthenium-catalyzed radical reactions in organic and polymer synthesis. 

Metathesis polymerization has become an important tool for polymer synthesis and has even attracted a Nobel Prize [46-49]. Acyclic diene molecules are capable of undergoing intramolecular and intermolecular reactions in the presence of appropriate transition metal catalysts, for example, molybdenum alkylidene and ruthenium carbene complexes. The intramolecular reaction, called ring-closing olefin metathesis (RCM), leads to cyclic compounds and the intermolecular reaction, called acyclic diene metathesis (ADMET) polymerization, leads to oligomers and polymers. Altering the dilution of the reaction mixture can to some extent control the intrinsic competition between RCM and ADMET. 

More recently, a soluble polymer (32) was prepared via reaction of l,l -ferrocenedimethanol with 4,4 -biphenyltetraamine in the presence of [RuCl2(P(C6115)3)3] (70). Approximately 20% of the iron centers were foimd to be in the Fe(III) state as a result of oxidation by ruthenium complexes formed during the polycondensation reaction. Wright and co-workers have reported the synthesis of ferrocene-based polymers possessing nonlinear optical properties (33) (71-73). These polymers were formed by polycondensation of a difunctionabzed ferrocene monomer (71). 

The synthesis of DCH-Ru polymers 5-8 was performed in the same manner as that of the comparable dinuclear ruthenium complexes previously reported, since early experimentation revealed that the poljdiydrazines were freely soluble in weak aqueous base solutions. The ruthenium-containing polymers were isolated by precipitation, but unfortunately could not be further purified by filtering through a neutral alumina-packed column as was used for purificaticm of DCH-Ru complexes. The DCH-Ru polymers were absorbed strongly on the alumina gels and therefore were used as synthesized for all physical characterization reported herein. 

Scheme 21 shows the synthesis of polystyrenes functionalized with cationic ruthenium complexes." These polymers (81) were prepared via coordination of Ru Cp, Ru CgHii, or Ru+H(PCy3)2 to the aromatic rings of polystyrene. Depending on the bulkiness of the hgand attached to rutheniiun, 25-90% of the aromatic rings in the polymers became complexed to the ruthenium. There have not yet been any reports on the polymerization of analogous styrene monomers. 

Polyamides and polyesters containing ruthenimn bipyridine complexes in their structures have been synthesized by Chan and coworkers." " Scheme 14 depicts the synthesis of polymer 64 by reaction of the metal-containing dicarboxylic acid complex 61 and the organic dicarboxylic acid (62) with an aromatic or aliphatic diamine (63). These polymers were thermally stable to temperatures between 320 and 500°C. Many of the polymers exhibited liquid crystalline characteristics. The photoconductivity of this class of polymer increased with increasing metal content." Chan also reported that polybenzo-bw-oxazoles and polybenzo-Z>w-thiazoles that contain ruthenium complexes coordinated to 2,2 bipyridyl units in the backbone... 

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