Session: Coordination Chemistry: Synthesis and Characterization:

Bimetallic nitrogen (N₂) splitting to form metal nitrides is an attractive method for N₂ fixation. Though a growing number of pincer-supported systems can bind and split N₂, the precise relationship between ligand properties and N₂ binding/splitting remains elusive. Here we report the first example of an N₂-bridged Re³⁺ complex, [(trans-P₂^tBuPyrr)ReCl₂]₂(μ-η¹:η¹-N₂) (P₂^tBuPyrr = [2,5-(CH₂P^tBu₂)₂C₄H₂N]^–). In this case, N₂ binding occurs at a higher oxidation level than in other reported pincer analogues. Analysis of the electronic structure through magnetism and computational studies shows that the weakly π-donor pincer ligand stabilizes an open shell electronic configuration that leads to enhanced binding of N₂ in the bridged complex. Reduction to Re²⁺ leads to a six-electron reduction of the N–N bond to form the terminal Re⁵⁺ nitride complex, (P₂^tBuPyrr)ReNCl.

Faraj Hasanayn

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