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DFT computation indicates the presence of solution equilibria with very low barriers when diiodine interacts with the square‐planar platinum(II) pincer complex Pt(NCN)I (NCN=[2,6‐bis{(dimethylamino)methyl}phenyl‐N,C,N]−) in dichloromethane. Species present include square‐planar Pt(NCN)(η1‐I3) and square‐pyramidal Pt(NCN)I(η1‐I2) interconverted via a triangular transition state with I2 bridging a Pt−I bond, and interaction of diiodine at the para‐position of the arene ring interconverted with Pt(NCN)I(η1‐I2) via a transition state with diiodine bridging the Cortho‐ and Cmeta‐positions. Similar facile intramolecular rearrangements occur for a model system with a molar ratio of 1 : 2 for Pt : I2, exhibiting species such as Pt(NCN)(η1‐I3)(η1‐I2) and mobility of diiodine over the (pincer)PtI plane. [ABSTRACT FROM AUTHOR]

Multistage mass spectrometry (MSn) experiments were used to explore extrusion-insertion (ExIn) reactions of the palladium complex [(phen)Pd(O2CPh)]+ (phen, 1,10-phenanthroline). Under collision-induced dissociation (CID) conditions, the organopalladium cation [(phen)Pd (Ph)]+ was formed via decarboxylation and was found to react with phenylmethylketene to yield the enolate [(phen)Pd(CPhMeC(O)Ph)]+ via an insertion reaction. A further stage of CID revealed that the enolate fragments via loss of styrene to form the acyl complex [(phen)Pd (C(O)Ph)]+. Formation of both the coordinated enolate and acyl anions is supported by density functional theory (DFT) calculations. Attempts to develop a palladium-mediated one-pot synthesis of ketones from 2,6-dimethoxybenzoic acid as the key substrate and the ketene substrates R¹R²"C"O (R¹ = Ph, R² = Me; R¹ = R² = Ph) proved challenging owing to low yields and side product formation. [ABSTRACT FROM AUTHOR]

Multistage mass spectrometry experiments, isotope labelling and DFT calculations were used to explore whether selective decarbonylation of formic acid could be mediated by molybdate anions [(MoO3)x(OH)]− (x = 1 and 2) via a formal catalytic cycle involving two steps. In step 1, both molybdate anions undergo gas-phase ion-molecule reactions (IMR) with formic acid to produce the coordinated formates [(MoO3)x(O2CH)]− and H2O. In step 2, both coordinated formates [(MoO3)x(O2CH)]− undergo decarbonylation under collision-induced dissociation (CID) conditions to reform the molybdate anions [(MoO3)x(OH)]− (x = 1 and 2), thus closing a formal catalytic cycle. In the case of [MoO3(O2CH)]− an additional decarboxylation channel also occurs to yield [MoO3(H)]−, which is unreactive towards formic acid. The reaction between [Mo18O3(18OH)]− and formic acid gives rise to [Mo18O3(O2CH)]− highlighting that ligand substitution occurs without 18O/16O exchange between the coordinated 18OH ligand and HC16O2H. The reaction between [(MoO3)x(OD)]− (x = 1 and 2) and DCO2H initially produces [(MoO3)x(OH)]− (x = 1 and 2), indicating that D/H exchange occurs. DFT calculations were carried out to investigate the reaction mechanisms and energetics associated with both steps of the formal catalytic cycle and to better understand the competition between decarbonylation and decarboxylation, which is crucial in developing a selective catalyst. The CO and CO2 loss channels from the monomolybdate anion [MoO3(O2CH)]− have similar barrier heights which is in agreement with experimental results where both fragmentation channels are observed. In contrast, the dimolybdate anion is more selective, since the decarbonylation pathway of [(MoO3)2(O2CH)]− is both kinetically and thermodynamically favoured, which agrees with experimental observations where the CO loss channel is solely observed. [ABSTRACT FROM AUTHOR]

The gas-phase extrusion–insertion (ExIn) reactions of the palladium complexes [(phen) n Pd(O2SC6H5)]+ (phen = 1,10-phenanthroline, n = 1 or 2), were investigated in the gas phase by multistage mass spectrometry (MS n ) experiments consisting of electrospray ionisation and a linear ion trap combined with density functional theory (DFT) calculations. Desulfination of palladium sulfinate cations under collision-induced dissociation (CID) generates the organopalladium intermediates [(phen) n Pd(C6H5)]+. Of these two organometallic cations, only [(phen)Pd(C6H5)]+ reacts with phenyl isocyanate via insertion to yield [(phen)Pd(NPhC(O)C6H5)]+. The formation of a coordinated amidate anion is supported by DFT calculations. In exploring this reactivity in the solution phase, we found that heating a mixture of benzenesulfinic acid, phenylisocyanate and palladium trifluoroacetate under a range of different conditions (ligand free versus with ligand, different solvents, addition of acid or base) failed to lead to the formation N -phenyl-benzamide in all cases. Instead, biphenyl was formed and could be isolated in a yield of 46%. DFT calculations using a solvent continuum reveal that the barrier associated with the insertion reaction lies above the competing sequential reactions of desulfination of a second phenyl sulfinate followed by reductive elimination of biphenyl. While gas-phase studies suggest that both palladium-mediated extrusion–insertion (ExIn) and condensation reactions operate for the generation of a N -phenyl-benzamide anion from the phenylsulfinate anion, a double desulfinative biaryl homocoupling reaction is favoured in the solution phase. [ABSTRACT FROM AUTHOR]

The present study describes a preparative gas chromatographic (GC) approach employed to study a series of products arising from reaction of phenylacetylene with para-substituted aryl-iodides under Sonogashira catalysis conditions. GC analysis resolves the isomers from each reaction; however, it cannot provide structural details (their MS data are virtually identical). Since classical liquid chromatography cannot resolve the isomers, preparative-scale GC is the only practical approach to provide further spectroscopic characterization of the isomers. The products are well separated by GC so a single thick-film capillary column is adequate for this case, with operation up to ~+300[degrees]C. By collection of 50+ repeat injections, sufficient material could be isolated for [sup.1]H NMR spectral analysis of the isomers, and for one isomer (isomer I) of a number of analogous related catalytic reaction mixtures, X-ray crystal structure determination enabled complete structural elucidation (absolute configuration) of the substitution pattern of the structure of this isomer. This confirmed isomer I to be the 2-para-aryl-substituted 1,3,5-triphenylbenzene product in all cases. [sup.1]H NMR spectra of isomer I products generally had similar patterns but differed markedly from the second major isomer product (isomer II). 10.1021/ac100417h

The synthesis of benzofurans by the reaction of the palladium(II) complex Pd{1-C6H4-2-OCH(CO2Et)-C,C}(bipy) (bipy = 2,2′-bipyridine) with hypervalent iodine(III) reagents [Ph(CH＝CHR)I]+ has been examined by Density Functional Theory. Results highlight the role of oxidative alkenylation to form PdIV intermediates and the role of initial adduct formation in this process, an annulation process facilitated by PdII, and the role of 'chain-walking' at PdII centres to allow formation of the lowest energy product. Computation (R = Me) allows assignment of an initially formed adduct with a 'PdII → IIII' interaction at −50 °C, and, after oxidative alkenylation of PdII and reductive elimination from a PdIV centre via Ar⋯Alkenyl coupling, formation of a second intermediate with a structure consistent with NMR detection (R = n-hexyl) at −30 °C is obtained. This PdII complex, containing a coordinated alkene group in Pd{1-(RHCγ＝Cβ)C6H4-2-OCαH(CO2Et)-η2-Cα＝Cβ,C}(bipy), undergoes a 5-exo-trig annulation by forming a Cα–Cβ bond to give a complex with a bicyclic carbon skeleton suitable for subsequent formation of benzofurans. A series of facile rearrangements including chain-walking results in formation of a lowest energy complex of three feasible hydrido(alkene)palladium(II) species, leading to decomposition and release of the observed benzofuran isomer isolated under synthesis conditions. The computational study allows reinterpretation of the NMR data reported previously, in particular the determination of barriers in the reaction pathway allowing assignment of structure for key intermediates. [ABSTRACT FROM AUTHOR]

Methyl(phenoxo)mercury(II) may be obtained from the reaction of methyl(chloro)mercury(II) with silver(I) oxide, followed by addition of phenol. The dominant motif of the structure is a pair of independent MeHgOPh aggregates (Hg--C,O 2.05(2) Å, 2.06(1) Å (x2); C-Hg-O 176.6(5)[??], 176.3(5)[??]) loosely associated about a quasi-inversion centre by Hg ... O interactions (2.702(9) Å, 2.719(9) Å) to form a dimer (Hg-O-Hg' 106.0(4)[??], 106.5(4)[??]; O-Hg-O' 73.0(3)[??], 72.6(3)[??]), the dimer stacking up the short crystallographic c axis (= 6.914(1)[??]) at spacings c/2. Vibrational spectroscopic studies are insensitive to the associative interactions. Key words: mercury, methylmercury, organomercury, structure, aryloxide, phenoxide. On peut obtenir du methyl(phenoxo)mercure(II) par reaction du methyl(chloro)mercure(II) avec de l'oxyde d'argent(I), suivie d'une addition de phenol. Le motif dominant de la structure est une paire d'agregats independants de MeHgOPh (Hg--C,O 2,05(2) Å, 2,06(1) Å (x2); C-Hg-O 176,6(5)[??], 176,3(5)[??]) faiblement associes autour d'un centre de quasi-inversion par des interactions Hg ... O (2,702(9) Å, 2,719(9) Å) qui permettent de former le dimere (Hg-O-HgN 106,0(4)[??], 106,5(4)[??]; O-Hg-ON 73,0(3)[??], 72,6(3)[??]) qui s'empile le long de l'axe cristallographique c (= 6,914(1) Å) a des distances de c/2. Les etudes spectroscopiques vibrationnelles sont insensibles aux interactions associatives. Mots cles : mercure, methylmercure, organomercure, structure, aryloxyde, phenolate. [Traduit par la Redaction], Introduction The coordination chemistry of monoorganomercury(II) complexes has been reviewed (1, 2); for arylalkoxides and aryloxides, structural studies are limited to the early study of the 4-bromo-2-chlorophenoxo complex PhHgO[C.sub.6][H.sub.3]ClBr (3, [...]