The $\ce{NR2}$ groups also act as pi donors with their formally electron pairs coupling to the molybdenum $4d$ orbitals (compare with the mesomeric effect of such groups in electrophilic aromatic substitution). Therefore the complex has fifteen electrons accessing the molybdenum valence orbitals. Under the threefold symmetry of the complex the three remaining vacant states split into an $a_1$ state and an $e$ pair, matching the symmetries of the bonding orbitals (apart from a center of inversion) in $\ce{N2}$.

The $\ce{NR2}$ groups also act as pi donors with their formally "lone" electron pairs coupling to the molybdenum $4d$ and $5p$ orbitals (compare with the mesomeric effect of such groups in electrophilic aromatic substitution). Therefore the complex has fifteen electrons accessing the molybdenum valence orbitals. Under the threefold symmetry of the complex the three remaining vacant states split into an $a_1$ state and an $e$ pair, matching the symmetries of the bonding orbitals (apart from a center of inversion) in $\ce{N2}$.