Complex, Tetraphenylporphyrin

The metalloporphyrin-catalyzed decomposition of ethyl azidoformate in the presence of an arene has been investigated but with little success in improving the yields of the 1 //-azepines.151 The nickel and copper complexes had no effect, whereas the cobalt-tetraphenylporphyrin complex accelerated the decomposition rate of the azido ester but produced more A-arylurethane rather than 1//-azepine. 

A regio-and stereoselective rearrangement of N-phenylspirooxaziridines 274 was reported by Suda [51e]. A Mn(III) tetraphenylporphyrin complex [Mn(tpp)Cl] served as activating reagent. Six- to eight-membered ketones 273 (n = 1,2,3) were converted into the corresponding seven- to nine-membered lactams 275 and... 

Alkali, alkaline-earth, and rare-earth metal cations also catalyze electron transfer reactions. Thus, in the pair of Co -tetraphenylporphyrin complex with BQ, no redox reaction takes place, or it takes place too slowly to be determined. The metal cations promote this reaction. For example, in the presence of 80(0104)3, the corresponding rate constant of 2.7 X 10 M s was observed. BQ transforms into benzosemiquinone under these conditions (Fukuzumi and Ohkubo 2000). Zinc perchlorate accelerates the reaction between aromatic amines and quinones (Strizhakova et al. 1985). This reaction results in the formation of charge-transfer complexes [ArNHj Q ]. The complexes dissociate in polar solvents, giving ion-radicals ... 

The meso-tetraphenylporphyrin complex [Zr(TPP)Cl2] has been prepared by reaction of H2TPP with ZrCl4 in boiling benzonitrile. The electronic spectrum of [Zr(TPP)Cl2] and the facile kinetics of TPP dissociation in acidic media suggest that the zirconium atom lies considerably out of the plane of the TPP ligand with both chlorine atoms being located on the same side of the TPP plane.708... 

The staggered conformation of terminal oxo ligands observed for MoVI in Mo203+ is not observed for Mov.12e However, in the tetraphenylporphyrin complex [Mo203(TPP)2] the linear Mo—O—Mo structure is retained, and the terminal oxo ligands lie trans to the ju-oxo group giving the opposed Ot—Mo—Ob—Mo—Ot structure.129... 

A number of workers have studied zinc tetraphenylporphyrin complexes, and an intensive study of the luminescence properties of [ZnTPP] has been reported.1180 [ZnTPP] is also used in the well-known synthetic leaf experiments.11806... 

It was reported that cobalt-tetraphenylporphyrin complex (CoTPP) coated on an electrode catalyzes electrocatalytic proton reduction,215 but the activity was not very high. We have found that metal porphyrins and metal phtahlocyanines when incorporated into a polymer membrane coated on an electrode show high activity in electrocatalytic proton reduction to produce H2.22,235 Some data are summarized in Table 19.2. It was shown that this catalyst is more active than a conventional platinum base electrode. 

Other novel initiators include the use of an aluminium-tetraphenylporphyrin complex Et—Al(TPP)12. Only D3 is polymerized at 25 °C over 6 days to give a monodispersed (.Mn/Mw = 1.12, Mn = 1550) polymer. D4 and D5 do not react under similar conditions and linear equilibration is suppressed. In addition, they report that this initiator will oligomerize functional cyclics such as (SiMeHO)4 and (SiPh20)3. 

Pt2(P205H2)4, also known as Pt2(POP)4, in the presence of tetrabutylam-monium (TBA) salts as electrolyte [19,20], ECL has also been observed from palladium and platinum a, 3,y,5-tetraphenylporphyrin complexes, and also via self-annihilation of the electrogenerated anion and cation radicals [21],... 

A novel synthesis of benzosultam 164 involves a Co-based catalytic system for intramolecular C-H animation with azides <07OL4889>. The commercially available cobalt tetraphenylporphyrin complex, Co(TPP) 163, is an effective catalyst for catalyzing C-H animation with arylsulfonyl azides 162 leading to benzosultams 164 in excellent yields. In addition to benzylic C-H bond, non-benzylic C-H bonds can also be intramolecularly aminated. For example, reaction of arylsulfonyl azides 165 with Co catalyst 163 results in a mixture of 5- and 6-membered ring products, 166 and 167. 

It has been found that in noncoordinating solvents, electron-donating substituents on the phenyl rings of substituted tetraphenylporphyrin complexes of Fe stabilize the complex, that is the Hammett p value is negative. This behavior is opposite to that typically expected for Lewis base reactions with Lewis acids, and in particular other metallotetraphenylporphyrins, including Niii 1436 opposite to that observed for... 

Kukufuta E and Nobusawa M. Uphill transport of phosphate ion through an oxomolybdenum(v)-tetraphenylporphyrin-complex-containing bulk liquid membrane Effect of halogen ions on phosphate ion flux. J Mem Sci, 1990 48(2-3) 141-154. 

Some of the earlier work on simpler models can be discussed in more detail here. Much of this focuses on the role of Met-80 in controlling the redox potential of cytochrome c. Low-spin tetraphenylporphyrin complexes of Fe" and Fe " with thioether axial ligands have similar bond lengths (Fe—S = 2.34 and 2.33, 2.35 A respectively). Increase in Fe—S bond length on going... 

A n.m.r. study of the substituted titanyl tetraphenylporphyrin complexes TiO(p-Pr -TPP) and TiOfp-CFj-TPP) showed that at 9 and 17 °C, respectively, rotation of the phenyl rings is slow enough to render the two sides of each ring non-equivalent. Peroxotitaniumoctaethylporphyrin has been prepared and its structure determined (see p. 14) the structure of titanyl octaethylporphyrin has also been determined. The Ti=0 bond is perpendicular to the porphyrin ligand... 

The extremely air-sensitive purple tetraphenylporphyrin complex, CrTPP, has been isolated by reduction of CrCl(TPP) with Cr(acac)2 in toluene or THF. Magnetic studies confirm the presence of Cr with = 4.8 BM for the high-spin d configuration. The other possibility, viz, a Cr radical anion derived from porphyrin ring reduction, was ruled out by electrochemical and visible absorption studies. ... 

Cobalt tetraphenylporphyrin complex promotes a chain-transfer reaction in the radical polymerization of MMA to give an MMA oligomer with vinylidene unsaturation at the chain end.124 An alternative method of introducing the terminal unsaturation was disclosed by Meijs et al,125 Substituted allylic sulphides are used as chain transfer agents in which sulphide groups act as leaving group as follows ... 

Figure 2.2 Simulated structure of the copper tetraphenylporphyrin complex...

The likelihood that alkyl radicals, like their aryl counterparts, bind to the iron before shifting to the nitrogen is supported by the observation that the type II complexes formed between alkyldiazenes and P450 in the absence of oxygen are converted, in the presence of limited amounts of oxygen, to complexes with an absorption maximum at 480 nm characteristic of iron-carbon o-bonded complexes Furthermore, alkyl diazene-iron tetraphenylporphyrin complexes can be prepared under anaerobic conditions. However, the alkyl-iron complexes are much less stable and less well characterized than the aryl-iron complexes and their involvement in heme iV-alkylation reactions remains to be demonstrated. 

Oxidation Potentials for Tetraphenylporphyrin Complexes Benzonitrile vs. SCE, Cyclic Voltammetry ... 

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