Carbon dioxide cleavage by a Ni 2 complex supported by a binucleating bis(N-heterocyclic carbene) framework

Abstract

A binucleating bis(N-heterocyclic carbene) ligand was designed as a means to coordinate and proximally constrain two transition metal centers. Using an imidazopyridine-based NHC afforded a framework structurally related to previously reported para-terphenyl diphosphines. Bimetallic copper, cobalt, and nickel complexes supported by this framework were synthesized and structurally characterized. Strong interactions between the metal centers and the central arene were observed in all nickel complexes. Dinickel(0) complexes of this ligand framework were found to react with CO2 to form a dicarbonyl-bridged dinickel(0) product, demonstrating facile CO2 reduction.

The 4-Electron Cleavage of a N═N Double Bond by a Trimetallic TiNi2 Complex

“…While there are numerous examples of d 10 –d 10 metal–metal interactions in coinage metals, there are significantly fewer with Ni. Complex 3 is among a limited number of formally Ni 0 –Ni 0 bimetallic complexes in the literature that feature short metal–metal distances. ,− The majority of these complexes are supported by bridging ligands that are strong π-acceptors such as CO, alkynes, nitriles, or isocyanides because there is no thermodynamic driving force for the formation of a metal–metal bond between two d 10 metal centers. In 3 , Ti could be envisioned as the bridging/supporting ligand.…”

N-Heterocyclic Carbene Complexes of Copper, Nickel, and Cobalt

“…In the dinuclear Cu I 2 complex 214 Cu prepared by deprotonation of the imidazolium salt with KOtBu in the presence of CuCl, the two Cu linear centers are occupying opposite faces of the arene, excluding any intermetallic interaction (Scheme 134). 302 A bis(NHC) proligand with a rigid m-phenylene linker has been synthesized as a potential precursor to pincer bis-NHC Scheme 130. Hydroxymethyl-Functionalized bis-NHC Complex 210 Cu complexes.…”

“…543 The binuclear diamagnetic Ni core took place, even though the identity of the oxygen atom acceptor was not pinned down (Scheme 267). 302 A series of binuclear Ni II 2 complexes with two atom bridges as part of the pyrazole-functionalized bis-NHC ligands were prepared by the reaction of the proligands 359 Ni with NaN(SiMe 3 ) 2 in the presence of [NiCl 2 (DME)] or via the synthesis of the Ag complexes followed by transmetalation to [NiCl 2 (DME)] or [NiCl 2 (PPh 3 ) 2 ] (Scheme 268). Pyridine-or picoline-substituted derivatives of 359 Ni under silver transmetalation conditions led to Ni 2 (μ-OH) cores with the bridging pyrazolyl-functionalized NHC ligand.…”

Intramolecular Arene Bonds of Complexes Featuring Terphenyl Bis(carbene) Macrocyclic Ligands

“…We were interested in the characteristics of bis­(carbene) ligands linked by a terphenyl for studying metal-arene interactions. Agapie and co-workers have synthesized a bis­(carbene) analogue of their terphenyl diphosphine ligand featuring a central arene (Figure C) . With the first-row transition metals copper, cobalt, and nickel, the bis­(carbene) ligand formed dinuclear complexes where the two metal centers either share the same face of the central phenyl or an opposite face of the central phenyl.…”