The coordination chemistry of unsymmetric N-capped tripodal NO3 ligands with iron(III), oxo-vanadium(V) and dioxo-molybdenum(VI) metal centres

The synthesis and characterisation of iron(III) [Fe(L1)]2 (1), oxo-vanadium(V) [VO(L1)] (2) and dioxo-molybdenum(VI) K[MoO2(L1)] (3) complexes supported by a partially unsymmetric N-capped tripodal NO3 ligand (L1) are reported. Complexes 1 and 2 were prepared by reactions of a proligand [H3L1] and their corresponding metal precursor (FeCl3 and VOCl3, respectively) in the presence of triethylamine in THF, while 3 was obtained in a similar manner by treating [MoO2(acac)2] (acac = acetylacetonate) with the same proligand and potassium hydroxide in methanol. The X-ray crystal structure of 1 illustrates a dimeric structure with a bis-(μ-phenoxo) Fe2O2 diamond core, and each iron centre bears a rare NO4 coordination sphere. The preparation of a previously unknown, fully unsymmetric N-capped tripodal NO3 proligand [H3L2] featuring three different phenolic arms is also described. Reaction of [H3L2] with VOCl3 yielded the oxo-vanadium(V) complex [VO(L2)] (4). Complexes 2–4 exist as monomers in solution and were characterised by NMR (1H and 13C), IR (for 3), mass spectrometry, and elemental analysis.