Titanium complexes porphyrins

Titanium(IV)-porphyrin [TiO(TPP)] as well as molybdenum(V)-porphyrin [MoO(OMe)(TPP)] complexes were found to be active for the catalytic epoxidation of alkenes by alkyl hydroperoxides, whereas their peroxo derivatives are inactive.632 Iron(III)-porphyrin-peroxo complexes such as Fe(TPP)02NMe4 did not react with hydrocarbons, but form sulfato complexes upon reaction with S02.632 Manganese(III)-porphyrin-peroxo complexes Mn(02)(TPP) K+ were recently characterized by X-ray crystallography.634... 

Convergent dendrimers, with their versatile three-dimensional scaffold, may be tailored to mimic, perhaps crudely, some elements of enzymatic structures. Numerous catalytic moieties, including manganese porphyrins,253,254 bis(oxazoline) copper complexes,304 305 tertiary amines,306 binaphthol titanium complexes,285 307 titanium taddolates,292,308 thiazolio-cyclophanes,309 and fullerene-bound bisoxazoline copper complexes,310 have been incorporated at the core of dendritic molecules to determine the effect of dendritic encapsulation on their catalytic activity. 

Some of the metallic constituents were somewhat soluble in the propane-oil portion, but all tended to be concentrated in the asphaltic portion. Although vanadium (0.02% by weight in the original crude petroleum) was present in all fractions, the greater part was found in the cyclohexane and benzene fractions. From the similarity of the absorption spectra of the vanadium concentrates from petroleum and those of synthetic vanadium porphyrin complexes, Skinner arrived at the conclusion that vanadium compounds from the petroleum of the Santa Maria Valley Field in California exist as porphyrin complexes. Additional metallic constituents were detected by Skinner as these became concentrated in the various solvent fractions, including aluminum, titanium, calcium, and molybdenum. 

The lack of adequate experimental data on chelates of germanium, boron, titanium, and vanadium prevents a similar comparison for these elements however, their high ionic potentials do indicate that they should form stable chelates. Vanadium does occur naturally in the very stable vanadium porphyrin complex. For similar reasons, molybdenum and tin are not discussed further. 

Dioxygen binds to metal porphyrins in the three expected modes, i.e. u-superoxo, peroxo and bridging peroxo. In contrast to die simple complexes discussed previously, dioxygen coordination occurs with a wide range of transition metals from titanium and niobium through to the Group VIII metals. 

Titanium can be inserted into a porphyrin by heating TiPh2Cl2, TiO(acac)2 or TiCL, in high boiling solvents.17 The complex is isolated as TiO(Por), which serves as a precursor of halide derivatives.36 The reaction of an oxotitanium porphyrin with benzoyl peroxide or hydrogen peroxide gives a peroxy compound (v(0—O) 895 cm-1). X-Ray structure analyses confirmed the triangular side-on structure with the O—O bond ( 1.45 A) parallel to one of the —Ti—directions. 

TV-phenylbenzohydroxamic acid, 506, phthalocyanines, 865 polypyrazolylborates, 248 porphyrins, 823 pseudohalides, 228 Titanium(III) complexes octaethylporphyrin reaction with dioxygen, 325 Titanium(IV) complexes 1,3-diketones, 376 triazines... 

H. J. Ledon, F. Varescon, Role of peroxo vs. alkylperoxo titanium porphyrin complexes in the epoxidation of olefins, Inorg. Client. 23 (1984) 2735. 

Molybdenum catalysts, Ruthenium porphyrins, Ruthenium(lll) complexes, Iron catalysts, Titanium catalysts. Sharpless epoxidation, Tungsten catalysts, Methyltrioxorhenium, Cobalt, Nickel, Platinum, Aerobic epoxidation, Lanthanum, Ytterbium, Calcium, BINOL-complexes. 2008 Elsevier B.v. 

Inoue et al. ( ) found that a porphyrin-Zn alkyl catalyst polymerized methyloxirane to form a polymer having syndio-rich tacticity. The relative population of the triad tacticities suggests that the stereochemistry of the placement of incoming monomer is controlled by the chirality of the terminal and penultimate units in the growing chain. There is no chirality around the Zn-porphyrin complex. Achiral zinc complex forms syndio-rich poly(methyloxirane), while chiral zinc complex, as stated above, forms isotactic-rich poly(methyloxirane). The situation is just the same as that for propylene polymerizations. Achiral vanadium catalyst produces syndiotactic polypropylene, while chiral titanium catalyst produces isotactic polypropylene. 

VIV. As with the titanium porphyrins, these complexes occur as vanadyl complexes with an axial oxo group and produce a "normal electronic spectrum which changes to a hematin spectrum when trifluoroacetic acid is added [Bonnett (9)]. The vanadyl porphyrins contain a single unpaired electron (/i=l,4B.M.) and their esr spectra have been studied in some detail [Kivelson (113a), Roberts (152)]. The rich redox chemistry of the inorganic vanadium salts is not reflected in the vanadyl porphyrins, where the +4 state seems to be exceptionally stable. 

---