New Titanium Catalysts Containing Tetrazole for Cycloaddition of CO₂ to Epoxides

Abstract

A series of new half-sandwich titanocene [(η5-C5H5)Ti L Cl2] (1) and nonorganometallic titanium complexes [Ti L Cl3(THF)] (2) and [Ti L 2Cl2] (3) containing 5-(2-hydroxyphenyl)tetrazole ( LH) were synthesized in high yield and fully characterized by various spectroscopic methods and X-ray crystallography. In all complexes, the ligand L acted as a monoanionic bidentate ligand and hydrogen bonding between the oxygen of the tetrahydrofuran and hydrogen of the tetrazolyl unit was observed. In the cycloaddition of CO2 to propylene oxide, complex 3 showed the highest activity among the reported Ti complexes.

Iron Catalysts Containing Pyridoxal Ligands for Cycloaddition of CO2 to Epoxides

“…A variety of metal complexes containing such metals as Zn, Al, Cr, and Co have been reported as efficient catalysts for the cycloaddition of CO 2 to epoxides . Recent research is focused on other metal catalytic systems, including Ti and lanthanide complexes . Iron is the most common element on earth, and it is considered as a nontoxic metal .…”

Zirconocene Complexes as Catalysts for the Cycloaddition of CO2 to Propylene Oxide

“…[16] Further studies to determine the effect of the cocatalyst on the catalytic activity were performed by using catalysts 1, 5, and 6 in the cycloaddition reaction (Table 1, entries 14-31). Six different kinds of cocatalysts including nBu 4 PBr, nBu 4 NCl, nBu 4 NBr, nBu 4 NI, PPNCl, and DMAP were used.…”

“…[15] Our group previously reported a novel Ti catalytic system containing tetrazoyl ligands with a high catalytic activity (turnover frequency, TOF = 422 h -1 ) at 75°C. [16] In an effort to develop group 4 metal catalytic systems, we focused on Zr complexes for the cycloaddition of CO 2 to epoxides. To the best of our knowledge, zirconocene complexes have never been used as catalysts for cyclic carbonates, though zirconium phosphate [17] has been used with an ionic liquid and zirconium BINOL (1,1Ј-bi-2-naphthol) complexes [18] have been used enantioselectively with other epoxides.…”

Phenyltetrazole as a New Ligand for Immobilization of Palladium Nanoparticles on SBA‐15: A New Robust Catalyst with High Loading of Pd for Rapid Oxidation and Reduction

“…Tetrazoles can be prepared through a cyclization process. These simple 4 nitrogen‐containing heterocycles may act as polydentate ligands for immobilization of transition metal, because of their aromaticity, excellent coordination capability and the possibility of offering new functionalized materials . Recently, there have been several reports on immobilization of Palladium nanoparticles on heterogeneous support applied in organic transformations.…”