Synthesis and Reactivity of a Pentacoordinated Thiolate-Based Imido-Alkylidene W(VI) Complexes

Attempt to synthesize a bis-thiolate tungsten alkylidene catalysts with bulky arenethiolates unexpectedly yielded upon activation of DME a pentacoordinated complex of general formula [W(NAr)(CHCMe3)(SAr’)(κ2-O-CH2-CH2-OMe)], which is active towards self-metathesis of cis-4-nonene compared to the parent bis-benzenethiolate

Synthesis and Reactivity of a Pentacoordinated Thiolate-Based Imido-Alkylidene W(VI) Complexes

International audienceAttempt to synthesize a bis-thiolate tungsten alkylidene catalysts with bulky arenethiolates unexpectedly yielded upon activation of DME a pentacoordinated complex of general formula [W(NAr)(CHCMe3)(SAr’)(κ2-O-CH2-CH2-OMe)], which is active towards self-metathesis of cis-4-nonene compared to the parent bis-benzenethiolate

Metal(II) Formates (M = Fe, Co, Ni, and Cu) Stabilized by Tetramethylethylenediamine (tmeda): Convenient Molecular Precursors for the Synthesis of Supported Nanoparticles

ISSN:0018-019XISSN:1522-267

Silica-Supported Pentamethylcyclopentadienyl Ytterbium(II) and Samarium(II) Sites: Ultrahigh Molecular Weight Polyethylene without Co-Catalyst

ISSN:1521-3757ISSN:0044-824

A reactive coordinatively saturated Mo(III) complex: exploiting the hemi-lability of tris(tert-butoxy)silanolate ligands

Coordinatively unsaturated Mo(III) complexes have been identified as highly reactive species able to activate dinitrogen without the need for a sacrificial reducing agent. Here, we report a coordinatively saturated octahedral Mo(III) complex stabilized by κ2-tris(tert-butoxy)silanolate ligands, which is yet highly reactive towards dinitrogen and small molecules. The combined high stability and activity are ascribed to the dual binding mode of the tris(tert-butoxy)silanolate ligands that allow unlocking a coordination site in the presence of reactive small molecules to promote their activation at low temperatures.ISSN:2041-6520ISSN:2041-653

Molecular and Supported Ti(III)–Alkyls: Efficient Ethylene Polymerization Driven by π-Character of Metal-Carbon Bonds and Back Donation from a Singly Occupied Molecular Orbital

Manuscript on a study on a homogeneous polymerization catalyst, its conversion to a heterogeneous catalyst by reaction with a support, an improvement of catalytic properties by this step, characterization of the structure of both catalysts, and insight into the mechanism of ethylene polymerization and its relation to electronic structure of intermediates. All important information for interpreting and reproducing the findings is contained in the main text and the supplementary information appended within the same PDF document.</div

Molecular and supported Ti(iii)-alkyls: efficient ethylene polymerization driven by the π-character of metal–carbon bonds and back donation from a singly occupied molecular orbital

ISSN:2041-6520ISSN:2041-653

C–H Activation and Proton Transfer Initiate Alkene Metathesis Activity of the Tungsten(IV)–Oxo Complex

International audienceIn alkene metathesis, while group 6 (Mo or W) high-oxidation state alkylidenes are accepted to be key reaction intermediates for both homogeneous and heterogeneous catalysts, it has been proposed that low valent species in their +4 oxidation state can serve as precatalysts. However, the activation mechanism for these latter species—generating alkylidenes—is still an open question. Here, we report the syntheses of tungsten(IV)–oxo bisalkoxide molecular complexes stabilized by pyridine ligands, WO(OR)2py3 (R = CMe(CF3)2 (2a), R = Si(OtBu)3 (2b), and R = C(CF3)3 (2c); py = pyridine), and show that upon activation with B(C6F5)3 they display alkene metathesis activities comparable to W(VI)–oxo alkylidenes. The initiation mechanism is examined by kinetic, isotope labeling and computational studies. Experimental evidence reveals that the presence of an allylic CH group in the alkene reactant is crucial for initiating alkene metathesis. Deuterium labeling of the allylic C–H group shows a primary kinetic isotope effect on the rate of initiation. DFT calculations support the formation of an allyl hydride intermediate via activation of the allylic C–H bond and show that formation of the metallacyclobutane from the allyl “hydride” involves a proton transfer facilitated by the coordination of a Lewis acid (B(C6F5)3) and assisted by a Lewis base (pyridine). This proton transfer step is rate determining and yields the metathesis active species