Octa-coordinated alkaline earth metal–dinitrogen complexes M(N2)8 (M=Ca, Sr, Ba)

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We report the isolation and spectroscopic identification of the eight-coordinated alkaline earth metal–dinitrogen complexes M(N 2 ) 8 (M=Ca, Sr, Ba) possessing cubic ( O h ) symmetry in a low-temperature neon matrix. The analysis of the electronic structure reveals that the metal-N 2 bonds are mainly due to [M(d π )]→(N 2 ) 8 π backdonation, which explains the observed large red-shift in N-N stretching frequencies. The adducts M(N 2 ) 8 have a triplet ( 3 A 1g ) 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 2 ) 8 ] + (M=Ca, Sr).