The three oxo groups as a tetrahedral set are classified as X6L2 (neutral representation, 8 electrons, σ and π-bonding) for the d-block metal rather than X6 (three X2 groups). The three oxygen atoms possess 12 valence orbitals (18 electrons) and may be treated as sp hybridised. Three (occupied) point away from the metal and are non-bonding (6 electrons). One of the π-orbitals is represented as A2, has no corresponding combination on the metal (2 electrons), and so non-bonding. The remaining ten electrons constitute the X6L2 class. Overall there are nine bonding orbitals (3A1 and 3E) in point group (C3v) connecting the three oxo groups set and one L-type ligand with the metal. This is very similar to the situation for imino complexes [M(X)(NX)3]. See:
- D.L. Morrison and D.E. Wigley, Inorg. Chem., 1995; 34, 2610–2616, https://doi.org/10.1021/ic00114a019.