Phthalocyanine complexe

In order to make these oxidative reactions of 1,3-dienes catalytic, several reoxidants are used. In general, a stoichiometric amount of benzoquinone is used. Furthermore, Fe-phthalocyanine complex or Co-salen complex is used to reoxidize hydroquinone to benzoquinone. Also, it was found that the reaction is faster and stereoselectivity is higher when (phenylsulflnyl)benzoquinone (383) is used owing to coordination of the sulfinyl group to Pd, Thus the reaction can be carried out using catalytic amounts of PdfOAcji and (arylsulfinyl)benzoquinone in the presence of the Fe or Co complex under an oxygen atmosphere[320]. Oxidative dicyanation of butadiene takes place to give l,4-dicyano-2-butene(384) (40%) and l,2-dicyano-3-butene (385)[32l]. 

Halide complexes are also well known but complexes with nitrogen-containing ligands are rare. An exception is the blue phthalocyanine complex formed by reaction of Be metal with phthalonitrile, 1,2-C6H4(CN)2, and this affords an unusual example of planar 4-coordinate Be (Fig. 5.5). The complex readily picks up two molecules of H2O to form an extremely stable dihydrate, perhaps by dislodging 2 adjacent Be-N bonds and forming 2 Be-O bonds at the preferred tetrahedral angle above and below the plane of the macrocycle. 

Indium phthalocyanine (PcInCl) can be prepared by treating indium(III) chloride with phthalonitrile in a high-boiling solvent like quinoline139 or 1-chloronaphthalene.143 Dimeric indium(III) phthalocyanine complexes of the type Pc2In,144 Pc3In2145 as well as a bicyclic phthalocyanine (Pc3/2ln)146 are also known. 

Bis(phthalocyanines) are also accessible by the reaction of isoindolinediimine and suitable metal compounds. For example, zirconium(IV) chloride when treated with isoindolinediimine in refluxing quinoline under a nitrogen atmosphere for 2 hours gives a zirconium(IV) bis(phthalocyanine) complex. 

Many Co11 porphyrins (87)110 131 and phthalocyanine complexes (102)110 have been examined for their ability to function as catalytic chain transfer agents and much mechanistic work has focused on the use of these catalysts. The more widespread application of these complexes has been limited because they often have only sparing solubility and they are highly colored. 

Several examples of carbene complexes have been structurally characterized (Fig. 5), and selected data for Ru(TPP)(=C(C02Et)2)(Me0H). Os(TTP)-(=C(p-C(,H4Me)2)(THF), Os(TTP)(=CHSiMe2)(THF), Os(TTP)(=SiEt2THF)-(THF) and a /x-carbido phthalocyanine complex, Ru(Pc)(py)]2C, are given in Table The ruthenium carbene complex has a Ru=C bond signifi-... 

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. 

Since iron phthalocyanine complexes can be activated and stabilized by a chlorine ring substitution (12), the activity of iron hexadecachlorophthalocyanine (7b) immobilized on silica was examined for the synthesis of 4, 5, and 6 with TBHP as oxidant. 

Coordination of NO to the divalent tetrasulfonated phthalocyanine complex [Co(TSPc)]4 results in a complex formally represented as [(NO )Coin(TSPc)]4 kf= 142M-1s-1, KA 3.0 x 105 M-1). When adsorbed to a glassy carbon electrode, [Co(TSPc)]4- catalyzes the oxidation and reduction of NO with catalytic currents detectable even at nanomolar concentrations. Electrochemistry of the same complex in surfactant films has also been studied.905 Bent nitrosyl complexes of the paramagnetic trivalent tropocoronand complex Co(NO)(TC) ((189), R = NO) have also been reported.849... 

Once again, a representative sample of zinc phthalocyanine complexes is presented highlighting particular areas of importance. 

The X-ray structure of zinc naphthalocyanate has been determined with Zn—N bond lengths of 1.983(4) A.829 Pentanuclear complexes with a zinc phthalocyanine core and four ruthenium subunits linked via a terpyridyl ligand demonstrate interaction between the photoactive and the redox active components of the molecule. The absorbance and fluorescence spectra showed considerable variation with the ruthenium subunits in place.830 Tetra-t-butylphthalocyaninato zinc coordinated by nitroxide radicals form excited-state phthalocyanine complexes and have been studied by time-resolved electron paramagnetic resonance.831... 

The redox potentials of zinc-substituted phthalocyanines are shown to be linearly dependent on the total Hammett substituent constant.837 In 1987, Stillman and co-workers used the absorption and magnetic circular dichroism spectra of the zinc phthalocyanine and its 7r-cation-radical species to assign the observed bands on the basis of theoretical calculations. The neutral and oxidized zinc phthalocyanine complexes with cyanide, imidazole, and pyridine were used with the key factor in these studies the stability of the 7r-cation-radical species.838 The structure of zinc chloro(phthalocyaninato) has been determined and conductivity investigated.839... 

The major types of complexes under intense investigation are the tetraden-tate Schiff base, for example, CoSalen, and phthalocyanine, for example, iron phthalocyanine complexes (Fig. 7.1).69... 

Metal Complexes with Macrocycles 9.10.4.2.1 Phthalocyanine complexes... 

Several metallophthalocyanines have been reported to be active toward the electroreduction of C02 in aqueous electrolyte especially when immobilized on an electrode surface.125-127 CoPc and, to a lesser extent, NiPc appear to be the most active phthalocyanine complexes in this respect. Several techniques have been used for their immobilization.128,129 In a typical experiment, controlled potential electrolysis conducted with such modified electrodes at —1.0 vs. SCE (pH 5) leads to CO as the major reduction product (rj = 60%) besides H2, although another study indicates that HCOO is mainly obtained.129 It has been more recently shown that the reduction selectivity is improved when the CoPc is incorporated in a polyvinyl pyridine membrane (ratio of CO to H2 around 6 at pH 5). This was ascribed to the nature of the membrane which is coordinative and weakly basic. The microenvironment around CoPc provided by partially protonated pyridine species was suggested to be important.130,131 The mechanism of C02 reduction on CoPc is thought to involve the initial formation of a hydride derivative followed by its reduction associated with the insertion of C02.128... 

Figure 8.4 The structure of metal-phthalocyanine complexes, with increased complexity adapting to the requirement of different metal ionic species.

Scheme 8.1 Three key methods of the synthesis of lanthanide(lll) bis(phthalocyanine) complexes. Homoleptic complexes symmetrical (A, B) and unsymmetrical (C1 and C2, D1). Thereby, the thermal fusion group A can be subdivided into (A1) solvent free fusion (A2) refluxing in the mixture of protic solvents in the presence of organic base - DBU and (A3) MW assisted fusion.

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