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High-level quantum chemical approaches are performed to study the stability and electronic structure of tri-, di-, monocationic, and neutral scandium ammonia complexes. The calculated binding energies of all Sc(NH 3 ) 1-8 3+,2+,+,0 complexes reveal the higher stability of hexa- and octacoordinated systems. The ground states of Sc(NH 3 ) 6,8 2+ and Sc(NH 3 ) 6,8 have a Sc 2+ (3d 1 ) center, while there are two competitive electronic states for Sc(NH 3 ) 6,8 + with a Sc 2+ (3d 1 ) or a Sc 3+ center. The remaining electrons occupy an outer diffuse s-type orbital (1s). The lower lying states involve 3d-3d transitions for Sc(NH 3 ) 6,8 2+ reduces the binding energies but shortens the Sc-N bond lengths. The comparison with the vanadium and yttrium ammonia complexes (studied earlier) reveal the unique identity of scandium balancing between a d- and s-block element.3 ) 6,8 +,0 . The addition of one electron to Sc(NH 3 ) 6,8 3+,2+,+ reduces the binding energies but shortens the Sc-N bond lengths. The comparison with the vanadium and yttrium ammonia complexes (studied earlier) reveal the unique identity of scandium balancing between a d- and s-block element.

The conversion of methane to methanol (MTM) catalyzed by FeOCH 3 + and FeCH 3 + is investigated by means of multireference configuration interaction (MRCI), single-reference coupled clusters (CC), and density functional theory (DFT) approaches. Our dual purpose is the assessment of the applied methodologies and the performance of the proposed catalytic cycle, which involves both of the titled units. The investigated cycle aims to bypass the limitations of metal-oxide catalysts and offers an alternative promising method for efficient MTM transformation. From the technical viewpoint, we found that generally accurate electron correlation treatment is more important than accurately calculated geometries. The combination of optimal DFT geometries with MRCI and CC energetics provides a good compromise between accuracy and efficiency, although there are cases where multireference calculations must be used to obtain correct structures.