Reversible C-CN Bond Cleavage by a Formal Dinickel(I) Hydride Cation

Area of Science:

• Organometallic Chemistry
• Catalysis
• Inorganic Chemistry

Background:

• N-heterocyclic carbenes (NHCs) are versatile ligands in organometallic chemistry.
• Dinickel complexes are of interest for their unique electronic structures and reactivity.
• Understanding metal-ligand interactions is crucial for catalyst design.

Purpose of the Study:

• To synthesize and characterize a stable dinickel hydride complex supported by an NHC ligand.
• To investigate the reactivity of the [Ni2H]+ core, particularly its protic character and interactions with nitriles.
• To elucidate the mechanism of C-CN bond cleavage in aliphatic nitriles.

Main Methods:

• Synthesis of the [Ni2H]+ complex using NHC ligands.
• Characterization via X-ray crystallography and spectroscopic techniques.
• Reactivity studies involving deprotonation and reactions with aliphatic nitriles.

Main Results:

• A stable, diamagnetic [Ni2H]+ cation with a bent hydride bridge and a Ni-Ni distance of 2.9926(5) Å was obtained.
• The complex exhibits weakly protic character, forming a (NHC)nickel(0) dimer upon deprotonation.
• Reaction with aliphatic nitriles leads to C-CN bond cleavage, suggesting nickel alkyl intermediates and reversible behavior.

Conclusions:

• The NHC ligand effectively stabilizes a dinickel(I) hydride core.
• The complex serves as a platform for studying C-CN bond activation.
• The observed reactivity provides mechanistic insights into nickel-catalyzed nitrile transformations.