Turning a New Leaf on Metal-TMC Chemistry: Ni^II(TMC) Acetylides

Abstract

Novel [Ni(TMC)C≡CY](+)-type compounds 1-4 [TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane; Y = SiMe3 (1), Si(i)Pr3 (2), Ph (3), and C2H (4)] have been synthesized and characterized. Single-crystal X-ray diffraction studies revealed that these compounds adopt a distorted square-pyramidal geometry, with the acetylide ligand occupying the apical position and a RSRS isomer for the TMC ligand. The room temperature magnetic properties of 1-4 are consistent with an S = 1 ground state, as corroborated by CASSCF and density functional theory calculations, which indicate that the singly occupied molecular orbitals are d(z(2)) and d(x(2)-y(2)).

Nickel Complexes of Pyridine‐Functionalized N‐Heterocyclic Carbenes: Syntheses, Structures, and Activity in Electrocatalytic Hydrogen Production

“…The square‐pyramidal geometry is commonly formed with pentadentate chelating ligands, or from a combination of tridentate and bidentate chelating ligands , . Square‐pyramidal structures formed by a tetradentate ligand with an additional halide ion are rather rare , . The non‐coordinating bromide ion and the lattice water molecules are connected with the coordinating bromide ion via hydrogen bonding interactions.…”

CoIII(cyclam) Oligoynyls: Monomeric Oligoynyl Complexes and Dimeric Complexes with an Oligoyn-diyl Bridge

“…While there are abundant examples of [M]–C 2 n –[M] systems based on 4d or 5d metals, systems based on redox-active 3d metals are dominated by Fe capping groups, with examples of other 3d metal end groups remaining sparse. Our interest has recently shifted from metal alkynyl chemistry based on diruthenium to 3d metal complexes based on the M­(cyclam) unit (cyclam = 1,4,8,11-tetraazacyclotetradecane) with the successful synthesis of new mononuclear Cr­(III), Fe­(III), Ni­(II), and Co­(III) , species, including complexes of scarcely studied cross-conjugated alkynes . These contributions, along with works from the laboratories of Wagenknecht, , Nishijo, Shores, and Berben/Long, have significantly expanded this previously underexplored frontier of 3d metal alkynyl chemistry.…”

Stepwise synthesis and catalysis in C–S cross-coupling of pyridine-functionalized N-heterocyclic carbene nickel(ii) complexes by mechanochemistry

“…To the best of our knowledge, the square-pyramidal structure with a tetradentate ligand and an additional halide ion is not commonly formed. 38,39 The overall structure was stabilized by extensive C–H⋯Br and C–H⋯F interactions (Fig. 2).…”