Octa-coordinated alkaline earth metal-dinitrogen complexes M(N<sub>2</sub>)<sub>8</sub> (M=Ca, Sr, Ba).

Wang, Qian; Pan, Sudip; Lei, Shujun; Jin, Jiaye; Deng, Guohai; Wang, Guanjun; Zhao, Lili; Zhou, Mingfei et al. · Nat Commun · 2019

basic_science · Level V

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Abstract

We report the isolation and spectroscopic identification of the eight-coordinated alkaline earth metal-dinitrogen complexes M(N<sub>2</sub>)<sub>8</sub> (M=Ca, Sr, Ba) possessing cubic (O<sub>h</sub>) symmetry in a low-temperature neon matrix. The analysis of the electronic structure reveals that the metal-N<sub>2</sub> bonds are mainly due to [M(d<sub>π</sub>)]→(N<sub>2</sub>)<sub>8</sub> π backdonation, which explains the observed large red-shift in N-N stretching frequencies. The adducts M(N<sub>2</sub>)<sub>8</sub> have a triplet (<sup>3</sup>A<sub>1g</sub>) electronic ground state and exhibit typical bonding features of transition metal complexes obeying the 18-electron rule. We also report the isolation and bonding analysis of the charged dinitrogen complexes [M(N<sub>2</sub>)<sub>8</sub>]<sup>+</sup> (M=Ca, Sr).