Structural and 13C NMR Studies on Palladium MOP Compounds: A New Weak C−Pd σ-Bond Plus MOP as a Bridging Diene Ligand

Bridging coordination of acenaphthylene to a Pd3 chain or a Pd4 sheet cluster

The coordination behaviour of multinuclear clusters to fused arene ligands is of continuous interest due to its relevance to metal catalysts supported by graphitic carbon materials. Herein, we report the bridging coordination behaviour of acenaphthylene to a Pd₃ or a Pd₄ cluster. A bis-acenaphthylene Pd₃ chain cluster and an acenaphthylene-COT Pd₄ sheet cluster were isolated, and the μ₃-π-coordination mode or the μ₄-oxidative π-addition mode of the acenaphthylene ligand in each cluster was elucidated by X-ray structure analysis.

Ratiometric electrochemical sensing based on Mo2C for detection of acetaminophen

In this work, MoO2 nanoparticles were synthesized and annealed to form Mo2C nanoparticles. This is the first report of a ratiometric electrochemical sensor (R-ECS) for the detection of acetaminophen (AP), in which Mo2C is used as the sensing agent and ferrocene (FC) is used as an internal reference. FC (100 μM) is added directly to the electrolyte solution for convenient operation. The synthesized materials were fully characterized with respect to composition, morphology and electrochemical performance. The oxidation peak potentials of FC (0.196 V) and AP (0.364 V) can be completely separated by the Mo2C modified glassy carbon electrode, and their ratiometric signals are used for the quantification of AP. It was found that the oxidation peak currents of AP at separated potentials on Mo2C/GCE are linear with concentration in the range of 0.5-600 μM, and the detection limit is 0.029 μM (S/N = 3). Mo2C/GCE exhibited decent repeatability, reproducibility, stability, and selectivity. The sensor was then applied to measure AP in tap water and river water.

Fluxional chloro-pyrrole–Pd(ii) complex to cationic η2-pyrrole–Pd(ii) complex: subtlety in structure-directed bonding mode

The fluxional pyrrole ring of a Pd(ii) complex produces a η²-pyrrole–Pd(ii) complex. It is the first report of a η²-pyrrole complex of Pd(ii).

Bimodal coordination of fused arenes to a Pd3 cluster site

We report bimodal coordination of fused arenes to a Pd₃ cluster site. The oxidative π-addition mode of anthracene and tetracene as well as the π-coordination mode of triphenylene and fluoranthene were identified.

Dipalladium(I) terphenyl diphosphine complexes as models for two-site adsorption and activation of organic molecules

A para-terphenyl diphosphine was employed to support a dipalladium(I) moiety. Unlike previously reported dipalladium(I) species, the present system provides a single molecular hemisphere for binding of ligands across two metal centers, enabling the characterization and comparison of the binding of a wide variety of saturated and unsaturated organic molecules. The dipalladium(I) terphenyl diphosphine toluene-capped complex was synthesized from a dipalladium(I) hexaacetonitrile precursor in the presence of toluene. The palladium centers display interactions with the π-systems of the central ring of the terphenyl unit and that of the toluene. Exchange of toluene for anisole, 1,3-butadiene, 1,3-cyclohexadiene, thiophenes, pyrroles, or furans resulted in well-defined π-bound complexes which were studied by crystallography, nuclear magnetic resonance (NMR) spectroscopy, and density functional theory. Structural characterization shows that the interactions of the dipalladium unit with the central arene of the diphosphine does not vary significantly in this series allowing for a systematic comparison of the binding of the incoming ligands to the dipalladium moiety. Several of the complexes exhibit rare μ-η(2):η(2) or μ-η(2):η(1)(O or S) bridging motifs. Hydrogenation of the thiophene and benzothiophene adducts was demonstrated to proceed at room temperature. The relative binding strength of the neutral ligands was determined by competition experiments monitored by NMR spectroscopy. The relative equilibrium constants for ligand substitution span over 13 orders of magnitude. This represents the most comprehensive analysis to date of the relative binding of heterocycles and unsaturated ligands to bimetallic sites. Binding interactions were computationally studied with electrostatic potentials and molecular orbital analysis. Anionic ligands were also demonstrated to form π-bound complexes.

Bridging π-coordination of pyrrole and indole over a Pd(I)-Pd(I) bond

π-Coordination of pyrrole or indole which lack a chelating functionality to a dinuclear Pd(I)-Pd(I) center is revealed. The dinuclear sandwich Pd(I)-Pd(I) complexes of pyrrole, N-methylpyrrole, or indole were synthesized and structurally characterized by X-ray crystallographic analysis. Indole employs the carbons of the six-membered ring in bridging π-coordination to a Pd(I)-Pd(I) center.

Oxidative dinuclear addition of a PdI-PdI moiety to arenes: generation of μ-η3:η3-arene-Pd(II)2 species

We report the oxidative dinuclear addition of a Pd(I)-Pd(I) bond to arenes. The oxidative dinuclear addition products, which have a bi-π-allyl-type arene dipalladium(II) structure, were obtained from [2.2]paracyclophane, anthracene, tetracene, and pentacene. A systematic study of the reaction of [Pd(2)(CH(3)CN)(6)][BF(4)](2) with benzene and polyacenes showed that the larger polyacenes, tetracene and pentacene, afforded the oxidative dinuclear addition products, while benzene, naphthalene, and anthracene gave the π-sandwich Pd(I)-Pd(I) complexes.

Stepwise Delivery of Two Methoxy Groups of Arylaldehyde Acetals across the Phenyl Ring. Vacant Site-Controlled Palladium Catalysis

A new catalytic cyclization of o-alkynylbenzaldehyde acetals 1 to the functionalized indenes 2 was found to be strictly controlled by the number of triphenylphosphine ligands on the Pd catalyst. Only complexes with three available coordination sites on Pd catalyze this reaction. Mechanistic study suggests that pi-coordination of Pd to the benzene ring is a key step controlled by the number of vacant coordination sites.