Palladium complexes phthalocyanines

Diazaporphyrins - Like the phthalocyanines, a 10,20-diaza-porphinoid palladium complex was composed by cyclooligomerization. The condensation of two suitable bispyrrole halves yielded the tetrapyrrole complex, cis [1,11-dimethoxy-2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18-hexadecamethyl- 10,20-diaza-decahydro-porphyrinato]palladium(II) [124]. 

The rich coordination chemistry of palladium provides a plethora of more or less readily available complexes, almost all applicable in type 1 or type 2 Mizoroki-Heck reactions. Only a limited series of truly robust and almost indefinitely stable ( dead ) palladium complexes, such as palladium porphyrinate or phthalocyanine complexes, as well as salen-type chelates with Schiff bases, are known not to release palladium even under the harshest conditions used in Mizoroki-Heck reactions. Results from the investigation of reactivity of... 

A mild aerobic palladium-catalyzed 1,4-diacetoxylation of conjugated dienes has been developed and is based on a multistep electron transfer46. The hydroquinone produced in each cycle of the palladium-catalyzed oxidation is reoxidized by air or molecular oxygen. The latter reoxidation requires a metal macrocycle as catalyst. In the aerobic process there are no side products formed except water, and the stoichiometry of the reaction is given in equation 19. Thus 1,3-cyclohexadiene is oxidized by molecular oxygen to diacetate 39 with the aid of the triple catalytic system Pd(II)—BQ—MLm where MLm is a metal macrocyclic complex such as cobalt tetraphenylporphyrin (Co(TPP)), cobalt salophen (Co(Salophen) or iron phthalocyanine (Fe(Pc)). The principle of this biomimetic aerobic oxidation is outlined in Scheme 8. 

Palladium, platinum, and silver pthalocyaninates - 5,6-Di-substituted isoindoles were condensed in the presence of Pd(acac)2 or PtCl2 to obtain soluble octa-alkoxy-substituted phthalocyaninato palladium(II) and platinum(II) complexes [121]. Tetrakis-(neopentyloxy) phthalocyaninatosilver(II) was obtained in high yield from AgN03 and the respective metal free phthalocyanine in DMF at 75 °C [122],... 

Zeolite-encapsulated Fe-phthalocyanine and Co-salophen catalysts were used in the palladium-catalyzed aerobic oxidation of hydroquinone to benzoquinone, in the oxidation of 1-octene to 2-octanone and in the allylic oxidation of cyclohexene to 3-acetoxycyclohexene. These catalysts proved to be active in the above reactions and they were stable towards selfoxidation and it was possible to reuse them in subsequent runs. The specific activity of the encapsulated Fe-phthalocyanine catalyst was about four times higher than those of the free complex. 

Palladium forms complexes such as the dithio-oxalate ion, Pd(N2S2H)2, glyoximes, and phthalocyanine which are structurally similar to the compounds of Ni and Pt, and also numerous bridged compounds. Early X-ray studies established the planar trans configuration of (d) and (e) ... 

Several metal macrocycles, like iron phthalocyanine and cobalt salophen were tested in these palladium-catalyzed aerobic oxidation of olefins and dienes. These tnacrocycles were able to activate the molecular oxygen, but in the homogeneous system several problems have arised, such as poor solubility, self-degradation and the difficulty to reuse theses complexes. A... 

Equations (II) to (IX) illustrate basic methods of preparation, but many variations are used, particularly in industry, to obtain an economic yield. Phthalic acid, phthalamide, phthalimide, and phthalic anhydride, together with urea, are often used instead of phthalonitrile, and catalysts such as ammonium molybdate or zirconium tetrachloride may be employed (249, 251, 269). The reaction between phthalonitrile and metals (finely divided or acid-etched) is usually very vigorous at 250°-300°C, sufficient heat being generated to maintain the reaction temperature. This is an illustration of the ease with which the phthalocyanine skeleton is formed. Even more surprising are the observations that palladium black (118) and gold (189) will dissolve in molten phthalonitrile. Reaction (III) between phthalonitrile and a finely divided metal, metal hydride, oxide, or chloride is perhaps the most generally employed. For the unstable phthalocyanine complexes such as that of silver (11), the double decomposition reaction... 

Palladium chlorophthalocyanine is formed when phthalonitrile is heated with palladous chloride. Like other nuclear halogen-substituted phthalocyanines, it will not sublime (11, 278). The unsubstituted derivative may be prepared by the dehydrogenation of tetracyclohexenotetrazaporphin with palladium black (113), or by the action of palladous chloride on lithium phthalocyanine in absolute alcohol (11). It is also possible to prepare the complex by dissolving palladium black in boiling phthalonitrile, a really remarkable reaction. 

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