Redox-state dependent activation of silanes and ammonia with reverse polarity (PCcarbeneP)Ni complexes: electrophilic vs. nucleophilic carbenes

A rigidified PCalkylP ligand allowed for the synthesis and charactarization of cationic and radical PCCarbeneP nickel complexes in which the carbene anchor of the pincer framework is electrophilic rather than nucleophilic. Alpha-hydride abstraction from (PCalkylP)nickel halide complex readily leads to the cationic carbene complex, which furnishes the radical carbene complex by one electron reduction. The reactivity of these reverse polarity carbene complexes towards small molecules (H2, CO, CO2, R3SiH, NH3) reveals different modes of activation when compared to previously reported nucleophilic nickel carbene complexes, and a clear dependence on the redox state of the complex. For H2, CO and CO2, no reaction is observed, but silanes react via hydride transfer and formation of solvated silylium ions. Ammonia is activated in a novel way, wherein it coordinates the carbene carbon and is deprotonated to form a robust C-N bond. This is not only a rare example of ammonia activation by a first row transition metal but also evidence of the intermediacy of group 10 carbenes in direct C-N bond forming reactions.

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Redox–state Dependent Activation of Silanes and Ammonia with Reverse Polarity (PCcarbeneP)Ni Complexes: Electrophilic vs. Nucleophilic Carbenes

10.26434/chemrxiv.6998441.v1 ◽

2018 ◽

Author(s):

Warren Piers ◽

Etienne A. LaPierre ◽

Chris Gendy

Keyword(s):

Small Molecules ◽

Redox State ◽

Reverse Polarity ◽

Carbene Complexes ◽

Carbene Complex ◽

Nucleophilic Carbenes ◽

Bond Forming ◽

State Dependent ◽

Hydride Abstraction ◽

Electron Reduction

A rigidified PCalkylP ligand allowed for the synthesis and charactarization of cationic and radical PCCarbeneP nickel complexes in which the carbene anchor of the pincer framework is electrophilic rather than nucleophilic. Alpha-hydride abstraction from (PCalkylP)nickel halide complex readily leads to the cationic carbene complex, which furnishes the radical carbene complex by one electron reduction. The reactivity of these reverse polarity carbene complexes towards small molecules (H2, CO, CO2, R3SiH, NH3) reveals different modes of activation when compared to previously reported nucleophilic nickel carbene complexes, and a clear dependence on the redox state of the complex. For H2, CO and CO2, no reaction is observed, but silanes react via hydride transfer and formation of solvated silylium ions. Ammonia is activated in a novel way, wherein it coordinates the carbene carbon and is deprotonated to form a robust C-N bond. This is not only a rare example of ammonia activation by a first row transition metal but also evidence of the intermediacy of group 10 carbenes in direct C-N bond forming reactions.

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Progress in preparation and characterization of silylene iron, cobalt and nickel complexes

Dalton Transactions ◽

10.1039/d1dt00523e ◽

2021 ◽

Author(s):

Wenjing Yang ◽

Yanhong Dong ◽

Hongjian Sun ◽

Xiaoyan Li

Keyword(s):

Nickel Complexes ◽

Electron Cloud ◽

Synthesis And Characterization ◽

Iron Cobalt ◽

Cloud Density ◽

Cobalt And Nickel

The synthesis and characterization of Fe, Co and Ni complexes supported by silylene ligands in recent ten years are summarized. Due to the decrease of electron cloud density on Si...

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