Bonding interactions between sulfur dioxide (SO2) and mono-ruthenium(ii)-substituted Keggin-type polyoxometalates: electronic structures of ruthenium–SO2 adducts

Abstract

Density functional theory (DFT) calculations and natural bond orbital (NBO) analysis were carried out to investigate the electronic structures and bonding features between the ruthenium(II) atom and the SO₂ molecule in two ruthenium–sulfur dioxide (SO₂) adducts, trans-Ru(NH₃)₄(SO₂)Cl⁺ and [{SiW₁₁O₃₉}Ru^II(SO₂)]⁶⁻. In addition, the bonding interactions between SO₂ and the metal-ruthenium fragment were determined by binding energy (ΔE_abs) calculation and electronic structures. The results indicate that the η¹-S-planar model in both trans-Ru(NH₃)₄(SO₂)Cl⁺ and [{SiW₁₁O₃₉}Ru^II(SO₂)]⁶⁻ are more favorable. NBO analysis of the bonding interaction between ruthenium and sulfur centers in the [{SiW₁₁O₃₉}Ru^II(SO₂)]⁶⁻ complex shows that it possesses a σ and a π bond. It predicts that the polyoxometalate [SiW₁₁O₃₉Ru]⁶⁻ can serve as a potential adsorbent for the SO₂ molecule because of the strong Ru–S bond relative to Ru(NH₃)₄Cl⁺.