Theoretical Study of Transition Metal Chemistry in Alkali Metal Complexes [K ₂ M(COT) ₂ ] ⁻ (M=K, Rb, Cs)

Abstract The transition metal properties of heavy alkaline earth metals have been extensively studied, and their neighbouring heavy alkali metals have been limited to the interactions with CO‐σ ligands. Based on this, the complexes [K 2 M(COT) 2 ] − (M=K, Rb, Cs) interacting with heavy alkali metals and COT‐π ligands are theoretically designed in this paper. The electronic structure analysis showed that the three complexes had 10 occupied molecular orbitals (MOs), in which 8 of them were related to the atomic orbitals (AOs) of central alkali metals, including 4 d orbitals (d xy , d x2−y2 , d xz , d yz ), so they also exhibited the typical behaviors of transition metals. NBO analysis indicated that the central metals in these complexes are common valence of +1, the ligands are negative, so the electrostatic coulomb interaction between positive and negative ions makes them more stable. This can be reflected by the high binding energies of −585.8 to −594.0 kcal/mol, which are much higher than those of −6.5 to −63.3 kcal/mol for the trace amount of complexes combined by neutral metals and ligands. It would be a feasible strategy for the design of the macrosynthesis of related complexes by combining the positive ions and negative ligands, which can stabilize the complexes through the favorable Coulomb attractions.