Cation-lone Pair Interaction in Alkali/Alkaline Earth Metal Ion-Heavier Borazine Analogue Complexes.

The present study is the first report on the formation of alkali/alkaline earth metal ion-heavier borazine analogue complexes via cation-lone pair interaction. Density functional calculations are performed in scrutinizing the complex formation between alkali (Li, Na, K)/alkaline earth (Be, Mg, Ca) metal ions and heavier borazine analogues (HBA) viz. BPH, AlNH, AlPH, AlAsH, and GaPH. The complexes are found to be stable in gas phase with stabilization energies within the range 26.40-324.74 kcal mol. The stability can be attributed to the polarizing power of the involved metal ions. Presence of solvent phase exerted notable impact on the stability of the complexes; stability is reduced significantly with the increase in solvent polarity. The process of complexation is exothermic and spontaneous. QTAIM analysis indicated the presence of both ionic and covalent interaction between HBAs and metal ions. HOMO energy, Wiberg bond index, NCI-isosurface and RDG plot analysis revealed the major role of cation-lone pair interaction in the complexation process.