Oxidative Imidation of Benzylic and Cycloalkane C(sp)-H Bond Donors Using -Aroyloxyquinuclidinium Salts and Nitriles under Photoredox Catalysis.

A series of -aroyloxyquinuclidinium salts were prepared and used as reagents to perform efficient three-component Ritter-Mumm-type oxidative C-H imidation of donors of 1° and 2° benzylic C-H bonds used as limiting reagents with nitriles as a source of imide nitrogen under photocatalytic conditions; these reagents also exhibit somewhat lower reactivity toward cycloalkanes.

Brownian translation and rotation from the ballistic to the diffusive limit and derivation of the physical properties of dust agglomerates.

We analyzed the translational and rotational Brownian motion of aggregates of micrometer-sized silica spheres under microgravity conditions and in rarefied gas. The experimental data was collected in the form of high-speed recordings using a long-distance microscope as part of the ICAPS (Interactions in Cosmic and Atmospheric Particle Systems) experiment on board of the sounding rocket flight Texus-56. Our data analysis shows that the translational Brownian motion can be used to determine the mass and translational response time of each individual dust aggregate.

Oxidative Trifluoroacetoxylation of 1°, 2°, and 3° Benzylic C(sp)-H Bond Donors Using -Trifluoroacetoxyquinuclidinium Salts under Photoredox Catalysis.

-Trifluoroacetoxyquinuclidinium trifluoroacetate was prepared from quinuclidine -oxide and (CFCO)O. Except for some electron-poor substrates, this reagent allows for the high-yielding oxidative trifluoroacetoxylation of 1°, 2°, and 3° benzylic C-H bonds under photocatalytic conditions. The trifluoroacetoxylation of an ibuprofen methyl ester allowed the selective functionalization of a 2° benzylic C-H bond.

Spectroscopic studies of methyl paraoxon decomposition over mesoporous Ce-doped titanias for toxic chemical filtration.

The ever-constant threat of chemical warfare agents (CWA) motivates the design of materials to provide better protection to warfighters and civilians. Cerium and titanium oxide are known to react with organophosphorus compounds such Sarin and Soman. To study the decomposition of methyl paraoxon (CWA simulant) on such materials, we synthesized ordered mesoporous metal oxides (MMO) TiO, CeTiO (x = 0.

Reversible Pt-CH deuteration without methane loss: metal-ligand cooperation ligand-assisted Pt-protonation.

Di(2-pyridyl)ketone dimethylplatinum(ii), (dpk)Pt(CH), reacts with CDOD at 25 °C to undergo complete deuteration of Pt-CH fragments in ∼5 h without loss of methane to form (dpk)Pt(CD) in virtually quantitative yield. The deuteration can be reversed by dissolution in CHOH or CDOH. Kinetic analysis and isotope effects, together with support from density functional theory calculations indicate a metal-ligand cooperative mechanism wherein DPK enables Pt-CH deuteration by allowing non-rate-limiting protonation of Pt by CDOD.

Aryl C(sp)-X Coupling (X = C, N, O, Cl) and Facile Control of N-Mono- and N,N-Diarylation of Primary Alkylamines at a Pt(IV) Center.

We present the first example of an unprecedented and fast aryl C(sp)-X reductive elimination from a series of isolated Pt(IV) aryl complexes (Ar = -FCH) LPtF(py)(Ar)X (X = CN, Cl, 4-OCHNO) and LPtF(Ar)(HX) (X = NHAlk; Alk = -Bu, PhCH, cyclo-CH, -Bu, cyclopropylmethyl) bearing a bulky bidentate 2-[bis(adamant-1-yl)phosphino]phenoxide ligand (L). The C(sp)-X reductive elimination reactions of all isolated Pt(IV) complexes follow first-order kinetics and were modeled using density functional theory (DFT) calculations. When a difluoro complex LPtF(Ar)(py) is treated with TMS-X (TMS = trimethylsilyl; X= NMe, SPh, OPh, CCPh) it also gives the corresponding products of the Ar-X coupling but without observable LPtF(py)(Ar)X intermediates.

An Electron-Poor Dioxa-[2.1.1]-(2,6)-pyridinophane Ligand and Its Application in Cu-Catalyzed Olefin Aziridination.

A novel macrocyclic 1,7-dioxa-[2.1.1]-(2,6)-pyridinophane ligand has been synthesized and crystallographically characterized.

Reductive C(sp)-N Elimination from Isolated Pd(IV) Amido Aryl Complexes Prepared Using HO as Oxidant.

Di-2-pyridyl ketone (dpk)-supported amidoarylpallada(II)cycles derived from various 2-(N-R-amino)biphenyls (R = H, Me, CFCO, MeSO, CFSO) react with hydrogen peroxide in MeOH, THF, MeCN or AcOH to form the corresponding C-N coupled products, N-R-substituted carbazoles, in 82-98% yield. For R = MeSO and CFSO, the corresponding reaction intermediates, amidoaryl Pd(IV) complexes were isolated and characterized by single crystal X-ray diffraction and/or NMR spectroscopy. For the first time, the C(sp)-N reductive elimination from isolated amidoaryl Pd(IV) complexes has been studied in detail.

Oxidation of a Monomethylpalladium(II) Complex with O2 in Water: Tuning Reaction Selectivity to Form Ethane, Methanol, or Methylhydroperoxide.

Photochemical aerobic oxidation of n-Pr4N[(dpms)Pd(II)Me(OH)] (5) and (dpms)Pd(II)Me(OH2) (8) (dpms = di(2-pyridyl)methanesulfonate) in water in the pH range of 6-14 at 21 °C was studied and found to produce, in combined high yield, a mixture of MeOH, C2H6, and MeOOH along with water-soluble n-Pr4N[(dpms)Pd(II)(OH)2] (9). By changing the reaction pH and concentration of the substrate, the oxidation reaction can be directed toward selective production of ethane (up to 94% selectivity) or methanol (up to 54% selective); the yield of MeOOH can be varied in the range of 0-40%. The source of ethane was found to be an unstable dimethyl Pd(IV) complex (dpms)Pd(IV)Me2(OH) (7), which could be generated from 5 and MeI.

Selective aryl-fluoride reductive elimination from a platinum(IV) complex.

A difluoro(mesityl)platinum(IV) complex underwent highly selective reductive elimination of 2-fluoromesitylene upon heating in toluene. Kinetic analysis and DFT calculations suggest that the CF coupling involves a five-coordinate Pt(IV) transient intermediate resulting from the rate-limiting dissociation of the pyridine ligand.

Mechanism of O2 activation and methanol production by (di(2-pyridyl)methanesulfonate)Pt(II)Me(OH(n))((2-n)-) complex from theory with validation from experiment.

The mechanism of the (dpms)Pt(II)Me(OH(n))((2-n)-) oxidation in water to form (dpms)Pt(IV)Me(OH)2 and (dpms)Pt(IV)Me2(OH) complexes was analyzed using DFT calculations. At pH < 10, (dpms)Pt(II)Me(OH(n))((2-n)-) reacts with O2 to form a methyl Pt(IV)-OOH species with the methyl group trans to the pyridine nitrogen, which then reacts with (dpms)Pt(II)Me(OH(n))((2-n)-) to form 2 equiv of (dpms)Pt(IV)Me(OH)2, the major oxidation product. Both the O2 activation and the O-O bond cleavage are pH dependent.

Unprecedented 1,3-migration of the aryl ligand in metallacyclic aryl α-naphthyl Pt(IV) difluorides to produce β-arylnaphthyl Pt(II) complexes.

Electrophilic fluorination of aryl α-naphthyl Pt(II) complexes leads to an unprecedented 1,3-migration of the aryl ligand to the β-position of the naphthyl group. The reaction proceeds via the initial oxidative addition of two fluoro ligands to the Pt center followed by C(sp(2))-C(sp(2)) coupling and aryl migration.

Electrophilic fluorination of organoplatinum(II) iodides: iodine and platinum atoms as competing fluorination sites.

A series of diphosphine Pt(II) aryl iodo complexes were reacted with XeF(2) to cleanly produce the corresponding Pt(II) difluoro complexes and free iodoarenes. However, when aryl ligands bearing fluoro substituents in the ortho positions were used, the formation of the corresponding Pt(II) aryl fluoro complexes was observed in the reaction with XeF(2). In the case of the Pt-C(6)F(5) complex, the products of the fluoride-for-iodide exchange were the only products observed by means of (31)P and (19)F NMR spectroscopy.

Oxidation of dimethyldi(2-pyridyl)borato Pt(II)Me(n) complexes, n = 1, 0, with H2O2: tandem B-to-Pt methyl group migration and formation of C-O bond.

New dimethyldi(2-pyridyl)borato (dmdpb) platinum(II) complexes, (dmdpb)Pt(II)Me(SMe(2)) (1), (dmdpb)Pt(II)(L)(SMe(2))(+), L = MeOH (2), MeCN (3), supported by dimethylsulfide ligand and featuring one (1) or no hydrocarbyls at the metal (2, 3) were prepared and their oxidation with hydrogen peroxide was studied. Both complex 1 bearing the formal charge of +1 on the metal and the methanol complex 2 capable of losing the proton of the methanol ligand to form the methoxide derivative 4 charged similarly to 1, are reactive towards H(2)O(2). However, the cationic complex 3 with a formal charge of +2 on the metal does not react with H(2)O(2).

Surprising acid/base and ion-sequestration chemistry of Sn9(4-): HSn9(3-), Ni@HSn9(3-), and the Sn9(3-) ion revisited.

K(4)Sn(9) dissolves in ethylenediamine (en) to give equilibrium mixtures of the diamagnetic HSn(9)(3-) ion along with K(x)Sn(9)((4-x)-) ion pairs, where x = 0, 1, 2, 3. The HSn(9)(3-) cluster is formed from the deprotonation of the en solvent and is the conjugate acid of Sn(9)(4-). DFT studies show that the structure is quite similar to the known isoelectronic RSn(9)(3-) ions (e.

Direct functionalization of M-C (M = Pt(II), Pd(II)) bonds using environmentally benign oxidants, O2 and H2O2.

Atom economy and the use of "green" reagents in organic oxidation, including oxidation of hydrocarbons, remain challenges for organic synthesis. Solutions to this problem would lead to a more sustainable economy because of improved access to energy resources such as natural gas. Although natural gas is still abundant, about a third of methane extracted in distant oil fields currently cannot be used as a chemical feedstock because of a dearth of economically and ecologically viable methodologies for partial methane oxidation.

Preparation and C-X reductive elimination reactivity of monoaryl Pd(IV)-X complexes in water (X = OH, OH2, Cl, Br).

Monohydrocarbyl palladium(IV) complexes bearing OH, OH(2), Br, and Cl ligands at the metal and supported by facially chelating 1-hydroxy-1,1-bis(2-pyridyl)methoxide were readily prepared in water at 0 °C. These complexes reductively eliminate Ar-X (X = OH, Br, Cl) in water at room temperature in high yield, and the corresponding first-order rate constants k(OH), k(Cl), and k(Br) are on the same order of magnitude.

Aryl-bromide reductive elimination from an isolated Pt(IV) complex.

A Pt(IV) complex bearing two aryl and two bromo ligands, which undergoes selective elimination of a bromoarene molecule has been prepared and fully-characterized. The mechanistic studies of this reaction are presented.

Homogeneous catalytic transfer dehydrogenation of alkanes with a group 10 metal center.

Unambiguous catalytic homogeneous alkane transfer dehydrogenation was observed with a group 10 metal complex catalyst, LPt(II)(cyclo-C6H10)H, supported by a lipophilic dimethyl-di(4-tert-butyl-2-pyridyl)borate anionic ligand and tert-butylethene as the sacrificial hydrogen acceptor.

Ligand-enabled Pt(II)-C(sp3) bond functionalization with dioxygen as a direct oxidant.

This feature article summarizes the progress achieved in the field of aerobic functionalization of Pt(II) monoalkyl complexes in protic solvents, water and alcohols. These functionalization reactions are possible in the presence of tripodal semi-labile ligands such as di(2-pyridyl)methanesulfonate (dpms). The reactions include two subsequent transformations: (i) direct (mediatorless) oxidation of a Pt(II) monoalkyl or a Pt(II)-oxetane to produce a Pt(IV)(OH) alkyl or a Pt(IV)(OH)-oxetane, respectively, and (ii) reductive elimination from the Pt(IV) center of an oxygenated organic derivative with a new C-O bond such as alcohols (MeOH, HOC2H4OH), ethers (Me2O), or olefin (ethylene, cis-cyclooctene, norbornene) oxides.

Catalytic aerobic oxidation of substituted 8-methylquinolines in Pd(II)-2,6-pyridinedicarboxylic acid systems.

The ability of Pd(II) complexes derived from 2,6-pyridinedicarboxylic acids to catalyze homogeneous regioselective aerobic oxidation of 5- and 6-substituted 8-methylquinolines in AcOH-Ac(2)O solution to produce corresponding 8-quinolylmethyl acetates in high yield was demonstrated; corresponding 8-quinoline carboxylic acids are minor reaction products.

Bidirectional transfer of phenyl and methyl groups between Pt(IV) and boron in platinum dipyridylborato complexes.

In the presence of weakly Lewis basic DMSO methyl group migration between B and PtIV in dipyridylborato trihydrocarbyl PtIV complexes is reversible; the preferred direction of Ph group migration in THF solution is from PtIV to B.

Competitive aryl-iodide vs aryl-aryl reductive elimination reactions in Pt(IV) complexes: experimental and theoretical studies.

The platinum(IV) complex trans-(dmpe)Pt(IV)(Ar)2I2 (2, dmpe = 1,2-dimethylphosphinoethane, Ar = 4-FC6H4) rapidly reacts, upon moderate heating in solution under ambient light, via two distinct pathways: isomerization to the corresponding cis-isomer (3) and Ar-I reductive elimination to give (dmpe)Pt(II)(Ar)I (4). Complex 3 undergoes, upon prolonged heating at high temperatures, an exclusive Ar-Ar reductive elimination reaction to give (dmpe)Pt(II)I2. Experimental and DFT studies showed that the 2-to-3 isomerization proceeds via three pathways: photochemical or thermal phosphine chelate opening and a mechanism involving cleavage of the Pt-I bond.