Porphyrinato complexes

Tetracyano ligands have been used to bridge between four Ru(NH3)5 moieties. The complexes [ Ru(NH3)5 4(/i-L)] + (L = tetracyanoethene, tetracyano-p-quinodimethane, 1,2,4,5-tetracyano-benzene, 2,3,5,6-tetracyanopyrazine) exhibit intense, long-wavelength electronic absorptions. Oxidation to [ Ru(NH3)5 4(yU-L)] °" " and reduction to [ Ru(NH3)5 4(//-L)] + and [ Ru(NH3)5 4-(/i-L)] + can readily be achieved. The species are fully delocalized with partially reduced ligands or partially oxidized Ru centers. Treatment of [5,10,15,20-tetrakis(4-cyanophenyl)porphyrinato] cobalt(II) or [5,10,15,20-tetrakis(4-cyano-2,6,-dimethylphenyl)porphyrinato]cobalt(II) with [Ru-(NH3)5(0S02CF3)] introduces cyano-bound pendant Ru (NH3)5 groups to the porphyrinato complexes. ... 

Oxidation of 2-methoxyethanol or 1,2-ethanediol by [0s04], in the presence of a porphyrin, is used to prepare [Osn(P)(CO)(X)] complexes [P is a porphyrinato(2-) ligand] (139). Recently, more convenient preparations of porphyrinato complexes were developed using the reactions of LOs3(CO)i2] with the appropriate porphyrin (Section II,C,4,d) (38, 40, 140,141). Electrochemical studies show that both the Os(III) and Os(III)/porphyrin-cation-radical complexes are moderately stable... 

Porphyrinato complexes containing alcoholate and alcohol ligands are discussed in Section II,C,4,d those containing cyano ligands are discussed in Section II,C,2,a, and those containing Schiff bases are... 

Interestingly, the analogous tetra-p-tolyl porphyrinato complex, which is known to form a p-oxo dimer upon oxygenation, was inactive as an oxygenation catalyst. This led the authors to conclude that inhibition of p-oxo dimer formation, via steric hindrance from bulky substituents in the porphyrin ring, is essential for catalytic activity. 

Manganese(V)-oxo-porphyrinato complexes have been presumed to be the active species in the epoxidation of alkenes by iodosylbenzene or hypochlorite catalyzed by manganese(III) porphyrins. This and related oxidations will be examined in more detail in Section 61.3.6.2.2. 

Porous polymers, supported tin hydrides, 9, 347 Porphyrinato complexes, with Zr(IV), 4, 809 Porphyrin-pyridylphosphines, inclusion chemistry, 12, 814 Porphyrins... 

The bis(porphyrinato) complexes of zirconium, Zr(OEP)2 and Zr(TPP)2, have a sandwich structure and have been... 

Detailed analyses of EPR spectra have been performed for [CrO(ehba)2] (ehba = 2-ethyl-2-hydroxybutanoato(2—)) (49b),155 194 195 [CrO(hca)2] (hcaH2= 1-hydroxycyclohexanecarboxylie-acid),196 [CrN(bpb)] (43), [Cr(N Bu )(bpb)Cl],140 and Crv porphyrinato complexes.197,198 Solution structures of the Crv complexes with 1,2-diolato or 2-hydroxycarboxylato complexes have been studied by H ENDOR spectroscopy.199,200 For the latter complexes, the existence of at least two geometric isomers in solutions has been detected,200 in agreement with the EPR spectroscopic... 

There have been relatively few developments in the chemistry of Cr111 porphyrinato complexes since 1985. Syntheses of new octahedral Crin-tpp derivatives (tpp = maso-tetra-phenylporphyrinato(2—)) used the well-known reactions of a five-coordinate (square pyramidal) [Cr(tpp)Cl] complex, such as the exchange of Cl- and/or the addition of a sixth neutral N- or O-donor ligand.1 481 The following complexes have been characterized by X-ray crystallography [Cr(tpp)Cl(py)],482 [Cr(tpp)Cl(MeIm)] (Melm = 1 -methyl- or 1,2-dimethylimidazoles),483... 

The oxo-transfer reactions (illustrated by equations (i) (iii) in Scheme 13) form the basis for the syntheses of stable Crlv porphyrinato complexes (equations (i) and (ii) in Scheme 13 see also Section 4.6.4.2.2), as well as for the use ofJCr(tpp)Cl] and related complexes in redox catalysis (Equations (ii) and (iii) in Scheme 13).1 496 497 The related nitrido-transfer reactions (Equation (iv) in Scheme 13) have also been observed.139,498,499... 

Mechanistic studies of one-electron oxidations or reductions of Cr111 porphyrinato complexes have been performed by pulse-radiolysis and electrochemical methods.500,501 The results (summarized in Equations (v)-(vii), Scheme 13) show that the reduction process can be directed either... 

The use of Cr111 porphyrinato complexes in catalysis became less prominent over the last 20 years due to developments in the Crin-salen and related systems (Section 4.6.5.8.4). The most... 

Lai, T.-S. Kwong, H.-L. Zhang, R. Che, C.-M. Stoichiometric enantioselective alkene epoxidation with a chiral dioxoruthenium(VI) D4-porphyrinato complex. Dalton Trans. 1998, 3559-3564. 

For iron(IlI)-porphyrinato complexes, strong-held ligands lead to low-spin (5 = 2) complexes. A pair of identical weak-held ligands, such as tetrahydro-furan, leads to intermediate-spin (5 = ) species. Five-coordinate species are, with few exceptions, high-spin (5 = f), with all hve 3d electrons in separate orbitals. Spin equilibria 5 = i 5 = f and 5 = 15 = i are not unusual. Specihc examples of these spin systems are given in Table 4.4. Higher oxidation states are found in some other hemoproteins. Fe(V)-porphyrin systems actually occur as Fe(IV)-porphyrin cation radical species, and Fe(I)-porphyrin systems exist as Fe(II)-porphyrin anion radical species. 

Iron(III) favours O-donor ligands and stable complexes such as the green [Fe(ox)3] and red [Fe(acac)3] are commonly encountered. Iron(III) porphyrinato complexes are of relevance for modelling haem-proteins (see Section... 

Lai, T.S., R. Zhang, K.K. Cheung, H.L. Kwong, and C.M. Che. Stoichiometric enantioselective alkene epoxidation with a chiral dioxoruthe-nium(VI) D-4-porphyrinato complex. J. Chem. Soc., Dalton Trans. 21, 3559-3564. 

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