Selectivity of tungsten mediated dinitrogen splitting vs. proton reduction

Area of Science:

• Inorganic Chemistry
• Catalysis
• Nitrogen Fixation

Background:

• Molybdenum complexes are leading catalysts for nitrogen fixation under ambient conditions.
• Tungsten-based catalysts for nitrogen fixation are less explored.
• Controlling selectivity between N2 reduction and proton reduction is a significant challenge in catalysis.

Purpose of the Study:

• To investigate nitrogen (N2) splitting using a tungsten pincer platform.
• To explore the reactivity of tungsten complexes in N2 activation and subsequent transformations.
• To understand the factors governing selectivity in N2 splitting versus proton reduction.

Main Methods:

• Synthesis and characterization of tungsten pincer complexes, specifically [WCl3(PNP)] (PNP = N(CH2CH2PtBu2)2).
• Activation of N2 to form dinitrogen-bridged tungsten complexes: [(N2){WCl(PNP)}2]0/+/2+.
• Protonation studies of the neutral dinitrogen complex under varying acidic conditions.

Main Results:

• Successful isolation and characterization of a dinitrogen-bridged tungsten complex series.
• Demonstration of N2 splitting via protonation, yielding either a tungsten nitride or H2 evolution.
• Identification of reaction pathways dependent on the specific acid and experimental conditions.
• Observation that hydrogen bonding influences the selectivity between nitrogen splitting and proton reduction.

Conclusions:

• Tungsten pincer platforms are effective for N2 splitting, a crucial step in catalytic nitrogen fixation.
• The selectivity of N2 splitting versus proton reduction is modulated by hydrogen bonding interactions.
• This study provides valuable insights and guidelines for designing efficient nitrogen fixation catalysts.