Pentacoordinated pyramidal structures and bonding properties of WN: anion photoelectron spectroscopy and theoretical calculations.

Anion photoelectron spectroscopy and theoretical calculations were used to investigate the structural and bonding properties of WN. The electron affinity of WN is measured to be 1.582 ± 0.030 eV. The frequency of the NN stretch in WN is measured to be 2170 ± 80 cm, which is red-shifted with respect to that of the dinitrogen molecule indicating that the NN bonds are weakened in WN. The theoretical adiabatic detachment energy (ADE) and vertical detachment energy (VDE) of WN obtained by calculations at the CCSD(T)/CBS level agree well with experimental results. The structures of WN are symmetric pentacoordinated pyramidal structures with five end-on dinitrogen ligands. Our experiments show that the peak of WN is dominant in the mass spectrum of anionic WN, whereas the mass peak of WN is dominant in the mass spectrum of cationic WN, implying that the stabilities of WN clusters are strongly related to their charge states.