A Novel Iron-Based Catalyst for the Biphasic Oxidation of Benzene to Phenol with Hydrogen Peroxide

Self-assembly of copper and cobalt complexes with hierarchical size and catalytic properties for hydroxylation of phenol

A feasible and effective self-assembly method to synthesize different scale coordination polymers in highly dilute solution (from nanocrystals to microcrystals and to bulk crystals) without any blocking agent has been described. The growth of crystalline particles was controlled by removing the particles at different reaction times to interrupt the growth at the desired size. The nano and microscale particles show better catalytic conversions and selectivities in the hydroxylation of phenols than the bulk crystals.

Synthesis and characterization of iron(II) quinaldate complexes

Treatment of iron(II) chloride or iron(II) bromide with 2 equiv of sodium quinaldate (qn = quinaldate or C(10)H(6)NO(2)(-)) yields the coordinatively unsaturated mononuclear iron(II) quinaldate complexes Na[Fe(II)(qn)(2)Cl].DMF and Na[Fe(II)(qn)(2)Br].DMF (DMF = N,N-dimethylformamide), respectively. When a similar synthesis is carried out using iron(II) triflate, a solvent-derived linear triiron(II) complex, [Fe(II)(3)(qn)(6)(DMF)(2)], with two five-coordinate iron(II) centers and a single six-coordinate iron(II) center is obtained. Each of these species has been characterized using X-ray diffraction. The vibrational features of these complexes are consistent with the observed solid-state structures. Each of these compounds exhibits an iron(II)-to-quinaldate (pi*) charge-transfer band between 520 and 550 nm. These metal-to-ligand charge-transfer bands are sensitive to substitution of the quinaldates as well as alteration of the first coordination sphere ligands. However, the (1)H NMR spectra of these paramagnetic high-spin iron(II) complexes are not consistent with retention of the solid-state structures in a DMF solution. The chemical shifts, longitudinal relaxation times (T(1)), relative integrations, and substitution of the quinaldate ligands provide a means to fully assign the (1)H NMR spectra of the paramagnetic materials. These spectra are consistent with coordination equilibria between five- and six-coordinate species in a DMF solution. Electrochemical studies are reported to place these oxygen-sensitive compounds in a broader context with other iron(II) compounds. Iron complexes of bidentate quinoline-2-carboxylate-derived ligands are germane to metabolic pathways, environmental remediation, and catalytic applications.

Fe-g-C3N4-catalyzed oxidation of benzene to phenol using hydrogen peroxide and visible light

A bioinspired iron-based catalyst with semiconductor photocatalytic functions in combination with a high surface area holds promise for synthetic chemistry via combining photocatalysis with organosynthesis. Here exemplified for phenol synthesis, Fe-g-C(3)N(4)/SBA-15 is able to oxidize benzene to phenol with H(2)O(2) even without the aid of strong acids or alkaline promoters. By taking advantage of both catalysis and photocatalysis functions of g-C(3)N(4) nanoparticles, the yield of the phenol can be markedly promoted.

A one-step conversion of benzene to phenol with a palladium membrane

Existing phenol production processes tend to be energy-consuming and produce unwanted by-products. We report an efficient process using a shell-and-tube reactor, in which a gaseous mixture of benzene and oxygen is fed into a porous alumina tube coated with a palladium thin layer and hydrogen is fed into the shell. Hydrogen dissociated on the palladium layer surface permeates onto the back and reacts with oxygen to give active oxygen species, which attack benzene to produce phenol. This one-step process attained phenol formation selectivities of 80 to 97% at benzene conversions of 2 to 16% below 250 degrees C (phenol yield: 1.5 kilograms per kilogram of catalyst per hour at 150 degrees C).