Phthalocyanines, synthesis catalysts

The catalytic formation of cyclic carbonates via aluminium porphyrins was probably the trigger for the investigation run by Kasuga and coworkers in 1996 with aluminium phthalocyanines as catalysts.In general phthalocyanines display the same planar N4-coordination geometry as the porphyrins as shown in Scheme 18.35 with the advantage of an easier synthesis and have been used in many homogeneous catalytic reactions. 

Previous studies by Sorokin with iron phthalocyanine catalysts made use of oxone in the oxidation of 2,3,6-trimethylphenol [134]. Here, 4 equiv. KHSO5 were necessary to achieve full conversion. Otherwise, a hexamethyl-biphenol is observed as minor side-product. Covalently supported iron phthalocyanine complexes also showed activity in the oxidation of phenols bearing functional groups (alcohols, double bonds, benzylic, and allylic positions) [135]. Besides, silica-supported iron phthalocyanine catalysts were reported in the synthesis of menadione [136]. 

We have demonstrated a new class of effective, recoverable thermormorphic CCT catalysts capable of producing colorless methacrylate oligomers with narrow polydispersity and low molecular weight. For controlled radical polymerization of simple alkyl methacrylates, the use of multiple polyethylene tails of moderate molecular weight (700 Da) gave the best balance of color control and catalyst activity. Porphyrin-derived thermomorphic catalysts met the criteria of easy separation from product resin and low catalyst loss per batch, but were too expensive for commercial implementation. However, the polyethylene-supported cobalt phthalocyanine complex is more economically viable due to its greater ease of synthesis. 

Continuous steam distillation, 147, 148 Cooling baths, 61 Cooling curve method, 26 Copper bronze, activated, 193 Copper - chromium oxide catalyst, for aldehyde synthesis, 318, 321 for hydrogenation, 872, 873 hydrogenolysis with, 872J Copper phthalocyanine, 983 Copper powder, 192 Copper sulphate, as desiccant, 40, 41 Cork stoppers, 55 boring of, 56... 

The use of heterogeneous catalysts in the synthesis of urethanes from aliphatic and aromatic amines, C02 and alkyl halides has been explored only recently. Titanosilicate molecular sieves [60a], metal phthalocyanine complexes encapsulated in zeolite-Y [60a], beta-zeolites and mesoporous silica (MCM-41) containing ammonium cations as the templates [60b, c], and adenine-modified Ti-SBA-15 [60d, e] each function as effective catalysts, even without any additional base. 

Two processes are commonly used for the production of copper phthalocyanine the phthalic anhydride-urea process patented by ICI [33,34] and the I.G. Farben dinitrile process [48], Both can be carried out continuously or batchwise in a solvent or by melting the starting materials together (bake process). The type and amount of catalyst used are crucial for the yield. Especially effective as catalysts are molybdenum(iv) oxide and ammonium molybdate. Copper salts or copper powder is used as the copper source [35-37] use of copper(i) chloride results in a very smooth synthesis. Use of copper(i) chloride as starting material leads to the formation of small amounts of chloro CuPc. In the absence of base, especially in the bake process, up to 0.5 mol of chlorine can be introduced per mole of CuPc with CuCl, and up to 1 mol with CuCl2. 

As apparatus for the batch process, an enamel or steel reactor with an agitator and pressure steam or oil heating suffices. Apparatuses used in the continuous synthesis in the presence of solvents and in the bake process are described in [50] and [51,52], respectively. The choice of process depends on the availability and cost of the starting materials phthalodinitrile or phthalic anhydride. Although the phthalodinitrile process has certain advantages over the phthalic anhydride process, the latter is preferred worldwide because of the ready accessibility of phthalic anhydride. In this process the molar ratio of phthalic anhydride, urea, and cop-per(i) chloride is 4 16 1, with ammonium molybdate as catalyst. The mixture is heated in a high-boiling solvent such as trichlorobenzene, nitrobenzene, or kerosene. The solvent is removed after the formation of copper phthalocyanine. Fre-... 

Di-iminoisoindoline was used as a precursor for Pc in different protic and aprotic systems, without catalysts or promoters, to study the solvent effect on the possibility of phthalocyanine formation [32], As can be observed (Example 13), it is possible to carry out the chemical and electrochemical synthesis of metal-free Pc in aprotic solvents, such as DMF or DMSO, in contrast to the results with PN. It is surprising that the yields of Pc in ROH are comparatively small. The N,N-dimethyletanolamine is characterized by the best yields, as in the case when PN was used as precursor. 

The Takai-Utimoto reaction of alkyl halides 360 with aldehydes 361 is a convenient method for the synthesis of branched alcohols 363 with high functional group tolerance [455]. Vitamin B12 362 or cobalt phthalocyanine served as the catalyst and CrCl2 as the stoichiometric reducing agent (Fig. 99). The reactions proceeded well with aromatic and aliphatic aldehydes. 

Over iron-phthalocyanine encaged in zeolite Y and using tertiary-butylhydroperoxide (t.-BHP) as oxidant, even cyclohexane can be converted to adipic acid. Selectivities of up to 35 % at conversions around 85 % have been reported. Unfortunately, however, a reaction time of 33 hours at 60 °C was required to achieve this conversion. Although the activity of the latter catalyst is certainly much too low to compete with the conventional catalytic systems for adipic acid synthesis, it provides interesting prospects for further developments. For the near future, we perceive that more and more groups will be working in this interesting field of catalysis by zeolite inclusion compounds. 

We have shown that perfluorination of the phthalocyanine ligand enhances the stability and catalytic activity of RuFiePc. Encapsulation of this complex in zeolite NaX by the synthesis method dramatically improves the activity and selectivity of RuFiePc. These results suggest that RuFi Pc-NaX is one of the best alkane oxidation catalysts of its kind. Although cycloalkanes are readily oxidized, the complete range of possible substrates is uncertain at this point. The oxidation of other alkanes and olefins will be the subject of continuing studies. 

Electrocatalysis at metal electrodes in aqueous (1.2) and non-aqueous ( ) solvents, phthalocyanine ( ) and ruthenium ( ) coated carbon, n-type semiconductors (6.7.8),and photocathodes (9,10) have been explored in an effort to develop effective catalysts for the synthesis of reduced products from carbon dioxide. The electrocatalytic and photocatalytic approaches have high faradaic efficiency of carbon dioxide reduction (1,6). but very low current densities. Hence the rate of product formation is low. Increasing current densities to provide meaningful amounts of product, substantially reduces carbon dioxide reduction in favor of hydrogen evolution. This reduction in current efficiency is a difficult problem to surmount in light of the probable electrostatic repulsion of carbon dioxide, or the aqueous bicarbonate ion, from a negatively charged cathode (11,12). 

Transition metal complexes of phthalocyanine encaged in faujasite type zeolites have been reported as efficient catalysts in the oxidation of alkanes at room temperature and atmospheric pressure [6-13]. These catalysts constitute potential inorganic mimics of remarkable enzymes such as monooxygenase cytochrome P-450 which displays the ultimate in substrate selectivity. In these enzymes the active site is the metal ion and the protein orientates the incoming substrate relative to the active metal center. Zeolites can be used as host lattices of metal complexes [14, 15]. The cavities of the aluminosilicate framework can replace the protein terciary structure of natural enzymes, thus sieving and orientating the substrate in its approach to the active site. Such catalysts are constructed by the so-called ship in a bottle synthesis the metal phthalocyanine complexes are synthesized in situ within the supercages of the zeolite... 

The hydroxylation reaction of phenol with hydrogen peroxide and zeolite encapsulated MePc has received considerable attention. With the perchlorinated phthalocyanine (ClnPc) and tetra-nitro ((N02)4Pc) substituted ligands, catalysts with superior activity have been obtained [32], Such catalysts have been prepared via the zeolite synthesis method around the individual complexes. With the former more bulky complex only the slimmer hydroquinone (HQ) has been obtained, while with the encapsulated perchloroPc equal ratios of catechol (CAT) and the para-isomer have been obtained (see table). The unsubstituted Pc in zeolite Y both with Co and Cu as metallating ion, show an excess of the ortho-isomer (CA T) [32J, corresponding to the approximate thermodynamic ratio. This points to the critical importance of the available space close to the encapsulated Pc as selectivity determining parameter when there is more space, the catalyst yields more catechol. 

Cobalt phthalocyanine has recently been employed as a catalyst to activate oxygen in a fuel cell (167a). Phthalocyanines have been used to develop a photographic method of Fourier synthesis (46) and have also been used in qualitative analysis (164). 

Polymeric phthalocyanines (Chap. 5.2) indude a great variety of properties. The construction of electrical devices or catalysts for spedal use is most hopeful. But all these applications depend on the reproduribility of well defined structural uniform polymers. Preparative work must help to standardize synthetic procedures and to investigate structures. The well reproducible in situ synthesis of thin layers of pure polymeric phthalocyanines from the gas phase opens a way for electrocatalysis and visible light energy changing devices. Another new kind of preparation goes via prepolymers which may be converted to mechanically and thermally stable, infusible polymers. 

Uses of bases of this type, such as DBU and DBN have been reviewed [15] and more recently they have been used as stoichiometric bases in the synthesis of 2H-isoindoles [ 16],biaryl thioethers [17],phthalocyanines [18] and the related macrocyclic compounds [18], 2,4-dioxo-l,2,3,4-tetrahydroquinazolines [19], dihydro alanine-containing peptides [20] and [[pyrazolylmethyl)amino]-propyl azepinones and -pyrrolidinones [21]. Chiral DBU/DBN-related molecules have also been synthesized which were fovmd to be useful as catalysts in an asymmetric Michael reaction [22]. 

More recently, Farrusseng and coworkers [119] described the encapsulation of large metal phthalocyanine (MPc) in the cavities of MIL-101 for the selective oxidation of tetrahn into 1-tetralone, a diesel fuel additive and an intermediate for the synthesis of agricultural chemicals (Figure 10.18). After a catalytic screening of different rmsupported metal phthalocyanine catalysts in aerobic tetralin oxidation, the MPc-MOF composite materials were prepared by wet infiltration of MPc... 

Besides their potential applicability as NLO materials noncentrosymmetri-cal phthalocyanines with different substituents on adjacent pairs of isoindole units promise intriguing new aspects in phthalocyanine chemistry polymeric phthalocyanines without crosslinking could lead to linear polymers, controlled binding of the phthalocyanine ring to a substrate could improve the synthesis of novel catalysts [188] and the preparation of highly ordered thin films should be possible [189]. 

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