New Alkylidyne Complexes Featuring a Flexible Trianionic ONO3– Pincer-Type Ligand: Inorganic Enamine Effect versus Sterics in Electrophilic Additions

Ligand-Dominated Activation of CO2 and CS2 by the Putative Nickel Phosphiniminato Intermediates

Room-temperature photoactivation of the first- and second-generation PN3P-pincer nickel azido complexes 1a and 1b in the presence of CO2 or CS2 afforded N-bound carbamates, dithiocarbamates, and isothiocyanates, providing insights into CO2 and CS2 activation and demonstrating how a seemingly small difference in the ligand structure significantly influences the reactivity. Theoretical calculations disclosed that the charge of the phosphorus atom plays a critical role in determining the nitrogen atom transfer to form a plausible nickel phosphiniminato intermediate.

Ring Expansion Alkyne Metathesis Polymerization

The synthesis, characterization, and preliminary activity of an unprecedented tethered alkylidyne tungsten complex for ring expansion alkyne metathesis polymerization (REAMP) are reported. The tethered alkylidyne 7 is generated rapidly by combining alkylidyne W(CtBu)(CH2tBu)(O-2,6-i-Pr2C6H3)2 (6) with 1 equiv of an yne-ol proligand (5). Characterized by NMR studies and nuclear Overhauser effect spectroscopy, complex 7 is a dimer. Each metal center contains a tungsten-carbon triple bond tethered to the metal center via an alkoxide ligand. The polymerization of the strained cycloalkyne 3,8-didodecyloxy-5,6-dihydro-11,12-didehydrodibenzo[a,e]-[8]annulene, 8, to generate cyclic polymers was demonstrated. Size exclusion chromatography (SEC) and intrinsic viscosity (η) measurements confirm the polymer's cyclic topology.

CO2 Cleavage Reaction Driven by Alkylidyne Complexes of Group 6 Metals and Uranium: A Density Functional Theory Study on Energetics, Reaction Mechanism, and Structural/Bonding Properties

Designing novel catalysts is essential for the efficient conversion of metal alkylidyne into metal oxo ketene complexes in the presence of CO₂, which to some extent resolves the environmental concerns of the ever-increasing carbon emission. In this regard, a series of metal alkylidyne complexes, [b-ONO]M≡CCH₃(THF)₂ ([b-ONO] = {(C₆H₄[C(CF₃)₂O])₂N}^3-; M = Cr, Mo, W, and U), have been comprehensively studied by relativistic density functional theory calculations. The calculated thermodynamics and kinetics unravel that the tungsten complex is capable of catalyzing the CO₂ cleavage reaction, agreeing with the experimental findings for its analogue. Interestingly, the uranium complex shows superior catalytic performance because of the associated considerably lower energy barrier and larger reaction rate constant. The M≡C moiety in the complexes turns out to be the active site for the [2 + 2] cyclic addition. In contrast, complexes of Cr and Mo could not offer good catalytic performance. Along the reaction coordinate, the M-C (M = Cr, Mo, W, and U) bond regularly transforms from triple to double to single bonds; concomitantly, the newly formed M-O in the product is identified to have a triple-bond character. The catalytic reactions have been extensively explained and addressed by geometric/electronic structures and bonding analyses.

An anionic nucleophilic d4 carbyne complex

The reaction of the methylidyne complex [W([triple bond, length as m-dash]CH)Br(CO)₂(dcpe)] (dcpe = 1,2-bis(dicyclohexylphosphino)ethane) with ^tBuLi affords the intermediate anionic neopentylidyne complex Li[W([triple bond, length as m-dash]C^tBu)(CO)₂(dcpe)] which acts as a metal-based nucleophile towards ^tBuCl, ^tBuBr, Ph₂E₂ (E = S, Se, Te) and ClSnMe₃ to afford the new carbyne complexes [W([triple bond, length as m-dash]C^tBu)(X)(CO)₂(dcpe)] (X = Cl, Br, EPh, SnMe₃).

A new ONO3− trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

This report details the synthesis and characterization of the semi-flexible [ON^CH2O]H₃ (1) ligand and its W(vi)-alkylidene and alkylidyne complexes.