High-Spin Iron(VI), Low-Spin Ruthenium(VI), and Magnetically Bistable Osmium(VI) in Molecular Group 8 Nitrido Trifluorides NMF3

Abstract

Pseudo-tetrahedral nitrido trifluorides N≡MF3 (M=Fe, Ru, Os) and square pyramidal nitrido tetrafluorides N≡MF4 (M=Ru, Os) were formed by free-metal-atom reactions with NF3 and subsequently isolated in solid neon at 5 K. Their IR spectra were recorded and analyzed aided by quantum-chemical calculations. For a d2 electron configuration of the N≡MF3 compounds in C3v symmetry, Hund's rule predict a high-spin 3A2 ground state with two parallel spin electrons and two degenerate metal d(δ)-orbitals. The corresponding high-spin 3A2 ground state was, however, only found for N≡FeF3, the first experimentally verified neutral nitrido FeVI species. The valence-isoelectronic N≡RuF3 and N≡OsF3 adopt different angular distorted singlet structures. For N≡RuF3, the triplet 3A2 state is only 5 kJ mol−1 higher in energy than the singlet 1A′ ground state, and the magnetically bistable molecular N≡OsF3 with two distorted near degenerate 1A′ and 3A“ electronic states were experimentally detected at 5 K in solid neon.