Dihydrogen Trioxide (HOOOH) Photoelimination from a Platinum(IV) Hydroperoxo-Hydroxo Complex

Photolysis (380 nm) of <i>trans-</i>Pt­(PEt₃)₂(Cl)­(OH)­(OOH)­(4-trifluoromethylphenyl) (<b>1</b>) at −78 °C in acetone-<i>d</i>₆ or toluene-<i>d</i>₈ yields HOOOH (16–20%) and <i>trans-</i>Pt­(PEt₃)₂(Cl)­(4-trifluoromethylphenyl) (<b>2</b>). Also observed in acetone-<i>d</i>₆ are H₂O₂, (CD₃)₂C­(OH)­(OOH), and (CD₃)₂C­(OOH)₂. Thermal decomposition or room-temperature photolysis of <b>1</b> gives O₂, water, and <b>2</b>. Computational modeling (DFT) suggests two intramolecular hydrogen-bonding-dependent triplet pathways for the photolysis and two possible pathways for the thermolysis, one involving proton transfer from the OOH to the OH ligand and the other homolysis of the Pt–OOH bond, abstraction of the OH ligand, and decomposition of the resulting H₂O₃. Trapping studies suggest the latter pathway

Hydroxo Radicals, C–H Activation, and Pt–C Bond Formation from 77 K Photolysis of a Platinum(IV) Hydroxo Complex

Photolysis (380 nm) of <i>trans</i>,<i>cis</i>-Pt­(PEt₃)₂(Cl)₂(OH)­(4-tft) (4-tft = 4-trifluoromethylphenyl) at 77 K in 2-methyltetrahydrofuran gives triplet emission, platinum­(III), and a hydroxo radical. Benzyl radical emission is observed in toluene from the reaction of a portion of the OH radicals with toluene. Warming the photolyzed solutions gives platinacycle <i>trans</i>-Pt­(CH₂CH₂PEt₂)­(PEt₃)­(Cl)₂(4-tft) by hydrogen-atom abstraction from a PEt₃ ligand and <i>trans</i>-Pt­(PEt₃)₂(Cl)­(4-tft) from net HOCl photoelimination. The platinacycle undergoes thermal reductive elimination at 298 K or photolytic reductive elimination, even at 77 K

Photoreduction of Pt(IV) Halo-Hydroxo Complexes: Possible Hypohalous Acid Elimination

Concentrated hydrogen peroxide addition to <i>trans-</i>Pt­(PEt₃)₂Cl­(R) [<b>1</b> (R = 9-phenanthryl), <b>2</b> (R = 4-trifluoromethylphenyl)] yields hydroxo-hydroperoxo complexes <i>trans-</i>Pt­(PEt₃)₂(Cl)­(OOH)­(OH)­(R) [<b>5</b> (R = 9-phenanthryl), <b>4</b> (R = 4-trifluoromethylphenyl)], where the hydroperoxo ligand is <i>trans</i> to R. Complex <b>5</b> is unstable and reacts with solvent CH₂Cl₂ to give <i>trans</i>,<i>cis</i>-Pt­(PEt₃)₂(Cl)₂(OH)­(9-phenanthryl) (<b>3</b>). Treatment of <b>4</b> with HCl yields analogous <i>trans</i>,<i>cis</i>-Pt­(PEt₃)₂(Cl)₂(OH)­(4-trifluoromethylphenyl) (<b>6</b>) and HBr gives <i>trans</i>-Pt­(PEt₃)₂(Br)­(Cl)­(OH)­(4-trifluoromethylphenyl) (<b>7</b>), where the Br and 4-trifluoromethylphenyl ligands are <i>trans</i>. Photolysis of <b>3</b> or <b>6</b> at 313 or 380 nm causes reduction to <i>trans-</i>Pt­(PEt₃)₂Cl­(R) (<b>1</b> or <b>2</b>, respectively). Expected coproduct HOCl is not detected, but authentic solutions of HOCl are shown to decompose under the reaction conditions. Chlorobenzene and other unidentified products that oxidize PPh₃ to OPPh₃ are detected in photolyzed benzene solutions. Photolysis of <b>3</b> or <b>6</b> in the presence of 2,3-dimethyl-2-butene (TME) yields the chlorohydrin (2-chloro-2,3-dimethyl-3-butanol), 3-chloro-2,3-dimethyl-1-butene, and acetone, all expected products from HOCl trapping, but additional oxidation products are also observed. Photolysis of mixed chloro-bromo complex <b>7</b> with TME yields the bromohydrin (2-bromo-2,3-dimethyl-3-butanol) and <b>2</b>, consistent with <i>cis</i>-elimination of HOBr. Computational results (TDDFT and DFT) and photochemistry of related complexes suggest a dissociative triplet excited state reaction pathway and that HOCl elimination may occur by an incipient hydroxo radical abstraction of an adjacent halogen atom, but a pathway involving hydroxo radical reaction with solvent or TME to generate a carbon-based radical followed by halogen abstraction from Pt cannot be eliminated

Hydroxyl Radical Control through Hydrogen Bonding: Photolysis of Platinum(IV)hydroxido Complexes with Intramolecular H‑Bonding

By introducing hydrogen-bonding groups into the coordination sphere of Pt­(IV) hydroxido complexes photogenerated hydroxyl radicals are tethered and directed to abstract a hydrogen atom from the ethyl group of a triethylphosphine ligand, even at 25 °C, to yield phosphaplatinacycle complexes

Calix[6]azacryptand Ligand with a Sterically Protected Tren-Based Coordination Site for Metal Ions

A new calix[6]azacryptand ligand has been prepared in six steps starting from 1,3,5-trismethoxycalix[6]arene. An X-ray study shows that this ligand has a sterically protected tren-based binding site at the bottom of a polyaromatic bowl and ether sites around its rim. It binds Zn2+ to give a complex in which zinc is in a trigonal bipyramidal geometry with a water bound in one apical position and two additional hydrogen-bonded waters that fill the calixarene cavity.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Reduction of Dinitrogen to Ammonia Catalyzed by Molybdenum Diamido Complexes

[Ar₂N₃]­Mo­(N)­(O-<i>t</i>-Bu), which contains the conformationally rigid pyridine-based diamido ligand, [2,6-(ArNCH₂)₂­NC₅H₃]^2– (Ar = 2,6-diisopropyl­phenyl), can be prepared from H₂[Ar₂N₃], butyllithium, and (<i>t</i>-BuO)₃Mo­(N). [Ar₂N₃]­Mo­(N)­(O-<i>t</i>-Bu) serves as a catalyst or precursor for the catalytic reduction of molecular nitrogen to ammonia in diethyl ether between −78 and 22 °C in a batchwise manner with CoCp*₂ as the electron source and Ph₂NH₂OTf as the proton source. Up to ∼10 equiv of ammonia can be formed per Mo with a maximum efficiency in electrons of ∼43%