Search results for " Metal"

Structural, photophysical and magnetic properties of transition metal complexes based on the dipicolylamino-chloro-1,2,4,5-tetrazine ligand

2015

International audience; The ligand 3-chloro-6-dipicolylamino-1,2,4,5-tetrazine (Cl-TTZ-dipica) 1, prepared by the direct reaction between 3,6-dichloro-1,2,4,5-tetrazine and di(2-picolyl)-amine, afforded a series of four neutral transition metal complexes formulated as [Cl-TTZ-dipica-MCl2]2, with M = Zn(II), Cd(II), Mn(II) and Co(II), when reacted with the corresponding metal chlorides. The dinuclear structure of the isostructural complexes was disclosed by single crystal X-ray analysis, clearly indicating the formation of [MII–(μ-Cl)2MII] motifs and the involvement of the amino nitrogen atom in semi-coordination with the metal centers, thus leading to distorted octahedral coordination geome…

An Entry to Mixed NHC-Fischer Carbene Complexes and Zwitterionic Group 6 Metal Alkenyls

2016

The addition of NHCs to α,β-unsaturated Cr(0) and W(0) (Fischer) carbene complexes is strongly dependent on the electrophilicity of the carbene carbon. Electrophilic alkoxy-carbene complexes quantitatively react with NHCs to yield stable zwitterionic (racemic) Cr(0) - and W(0) -alkenyls with total regio- and E-stereoselectivity. Less electrophilic aminocarbenes react with NHCs to promote the displacement of a CO ligand and yield "mixed" NHC/Fischer biscarbenes in a process that is unprecedented in group 6 metal-carbene chemistry. In fact, the compounds prepared, are some of the scarce examples of Fischer bisylidenes reported in the literature. The electrochemistry of the zwitterionic Cr(0) …

2015

Biphenols are important structure motifs for ligand systems in organic catalysis and are therefore included in the category of so-called "privileged ligands". We have developed a new synthetic pathway to construct these structures by the use of selenium dioxide, a stable, powerful, and commercially available oxidizer. Our new, and easy to perform protocol gives rise to biphenols and diaryl selenides depending on the solvent employed. Oxidative treatment of phenols in acetic acid yields the corresponding biphenols, whereas conversion in pyridine results in the preferred formation of diaryl selenides. As a consequence, we were able to isolate a broad scope of novel diaryl selenides, which cou…

2021

A nickel complex incorporating an N2 O ligand with a rare η2 -N,N'-coordination mode was isolated and characterized by X-ray crystallography, as well as by IR and solid-state NMR spectroscopy augmented by 15 N-labeling experiments. The isoelectronic nickel CO2 complex reported for comparison features a very similar solid-state structure. Computational studies revealed that η2 -N2 O binds to nickel slightly stronger than η2 -CO2 in this case, and comparably to or slightly stronger than η2 -CO2 to transition metals in general. Comparable transition-state energies for the formation of isomeric η2 -N,N'- and η2 -N,O-complexes, and a negligible activation barrier for the decomposition of the lat…

Interactions of a Diplumbyne with Dinuclear Transition Metal Carbonyls to Afford Metalloplumbylenes

2020

The metathesis reactions of the diplumbyne AriPr6PbPbAriPr6 (AriPr6 = −C6H3–2,6-(C6H2–2,4,6-iPr3)2) with the dinuclear metal carbonyls Mn2(CO)10, Fe2(CO)9, and Co2(CO)8 under mild conditions afforded the complexes Mn(CO)5(PbAriPr6) (1), Fe(CO)4(PbAriPr6)2 (2), and Co4(CO)9(PbAriPr6)2 (3), respectively. Complexes 1–3 were structurally characterized by single-crystal X-ray diffraction and spectroscopically characterized by 1H, 13C{1H}, 59Co{1H}, and 207Pb{1H} NMR; UV–vis; and IR methods. They are rare examples of species formed by the direct reaction of a group 14 dimetallyne with transition metal carbonyls. Complexes 1 and 2 feature Mn–Pb or Fe–Pb single bonds, whereas in 3 a Co–Pb cluster i…

Reappraising Schmidpeter's bis(iminophosphoranyl)phosphides: coordination to transition metals and bonding analysis

2020

The synthesis and characterization of a range of bis(iminophosphoranyl)phosphide (BIPP) group 4 and coinage metals complexes is reported. BIPP ligands bind group 4 metals in a pseudo fac-fashion, and the central phosphorus atom enables the formation of d0–d10 heterobimetallic complexes. Various DFT computational tools (including AIM, ELF and NCI) show that the phosphorus–metal interaction is either electrostatic (Ti) or dative (Au, Cu). A bridged homobimetallic Cu–Cu complex was also prepared and its spectroscopic properties were investigated. The theoretical analysis of the P–P bond in BIPP complexes reveals that (i) BIPP are closely related to ambiphilic triphosphenium (TP) cations; (ii) …

Light-Induced Alkylation of (Hetero)aromatic Nitriles in a Transition-Metal-Free C–C-Bond Metathesis

2017

A light-induced C–C-σ-bond metathesis was achieved through transition-metal-free activation of an unstrained C(sp3)–C(sp3)-σ-bond in 1-benzyl-1,2,3,4-tetrahydroisoquinolines. A photoredox-mediated single-electron oxidation of these precursor amines yield radical cations which undergo a homolytic cleavage of a C(sp3)–C(sp3)-σ-bond rather than the well-known α-C–H-scission. The resulting carbon-centered radicals are used in the ipso-substitution of (hetero)aromatic nitriles proceeding through another single-electron transfer-mediated C–C-bond cleavage and formation.

Anodic Degradation of Lignin at Active Transition Metal-based Alloys and Performance-enhanced Anodes

2018

Automated Diffraction Tomography for the Structure Elucidation of Twinned, Sub-micrometer Crystals of a Highly Porous, Catalytically Active Bismuth M…

2012

Fluorescence Quenching in BODIPYs Having Ir‐ and Rh‐Tethered Complexes

2016

The effect of Rh- and Ir-centers on the optical properties of the BODIPY core has been studied. To this end, novel metal complexes tethered to BODIPY have been prepared through an easy and versatile procedure using N-directed C–H activation reactions. The organometallic moiety has a tremendous influence on the emissive properties of the BODIPY fragment. A photoinduced electron transfer (PET) mechanism is suggested to be the main mechanism responsible for the suppression of the BODIPY fluorescence emission in the newly formed dyads. The efficiency of the PET depends on both the distance between the chromophores in the dyad and the nature of the transition metal (Rh vs. Ir).