Octaethylporphyrin

Of great importance for porphyrin chemistry is the introduction of carbon substituents by Vilsmeier formylation100 or Friedel-Crafts acylation.100 The introduced substituents allow further carbon-chain elongations and other transformations so that interesting porphyrin derivatives can be synthesized. The Vilsmeier formylation of copper octaethylporphyrin (5) takes place at themethine position. The copper can then be easily removed by treatment with acid.105... 

Chlorins are also accessible by carbene additions to C-C double bonds on the periphery of metalloporphyrins. The most effective reaction on a preparative scale is the addition of ethyl diazoacetate in refluxing benzene to copper octaethylporphyrin (4) or meso-tetraphenylpor-phyrin in the presence of copper(I) iodide,100108b 110 which gives a diastereomcric mixture of chlorins, e.g. 5. 

A mixture of 2,3.7,8.12,13.17.18-octaethylporphyrin (1. M = H2 500 mg. 0.94 mmol), anhyd K2CO, (3.8 g. 27 mmol) and freshly distilled 3-methylpyridine (25 inL) was refluxed under N2 and a solution of p-lol-uenesulfonylhydrazide (5.0 g. 27 mmol) in 3-mcthylpyridine (15 mL) was added dropwise over a period of 2.5 h. The mixture was refluxed for a further 2 h, cooled and extracted with benzene, which was washed with cold dil HC1 and extracted with 85% H3P04 (3 x 35 mL). The combined aqueous extracts were diluted to 60 % H3P04 (by addition of 40 mL of H20) and extracted with benzene. The benzene extracts were then washed with 60% H2P04 and H20 and evaporated to dryness. Crystallization (CHCI, /MeOH) gave the title compound yield 56 mg (11 %). 

The formal addition of a methane molecule to a ft-pyrrolic C — C double bond can be achieved when bishydroxytin(IV) octaethylporphyrin 17 is first treated with a chloroform/aluminum tribromide mixture to give 18 which can subsequently be reduced with sodium borohydride and dcmctalated with acid to give the methylated chlorin 19.23... 

The oxidation of octaethylporphyrin 418 with hydrogen peroxide in sulfuric acid leads under pinacol rearrangement to a mixture of hydroporphyrinones, among them the expected three constitutionally isomeric isobacteriochlorins. 

Porphyrin complexes have been the most intensively studied macrocyclic complexes of these metals [129]. They are formed in a wide range of oxidation states (II-VI) and they are, therefore, treated together under this heading, though most of the chemistry for ruthenium lies in the II-IV states. Octaethylporphyrin (OEP) complexes are typical. 

The olive-green osmium(VI) octaethylporphyrin complex 0s02(0EP) (IR v(0s—0) 825 cm-1) is representative of a number of osmyP porphyrins [185] they can readily be transformed into a number of osmium porphyrins in lower oxidation states (Figure 1.73). 

Photolysis of the rhodium(III) complex of octaethylporphyrin gives a rhodium(II) dimer that readily undergoes addition reactions to afford rhodium(III) species (Figure 2.42). 

Figure 2.42 Synthesis of a dimeric rhodium(II) octaethylporphyrin complex.

Reaction of [Rh(CO)2Cl]2 with porphyrins (e.g. H2TPP) leads to Rh(por-phyrin)(CO)Cl, which readily lose CO. Some of the chemistry of the octaethylporphyrin complexes [102] is shown in Figures 2.51 and 2.52. 

With their preference for square planar coordination, palladium(II) and platinum(II) are well suited to binding to porphyrins and related N4 donor macrocycles. Therefore, Pd(octaethylporphyrin) is readily synthesized starting from the labile PhCN complex (like the platinum analogue) [92]... 

---