Bonding Interactions between Nitrous Oxide (N ₂ O) and Mono‐Ruthenium Substituted Keggin‐Type Polyoxometalates: Electronic Structures of Ruthenium/N ₂ O Adducts

Density functional theory (DFT) calculations were performed for three ruthenium/nitrous oxide(N 2 O) adducts, Ru II Cl 2 (η 1 ‐N 2 O)(P–N)(PPh 3 ) {P–N = [ o ‐(dimethylamino)phenyl]diphenylphosphane} ( 1 ), Ru II (η 1 ‐N 2 O)(TMP)(THF) (TMP = dianion of tetramesitylporphyrin, THF = tetrahydrofuran) ( 2 ), and [PW 11 O 39 {Ru II/ (η 1 ‐N 2 O/H 2 O)}] n – ( 3 ). The bonding interactions between the N 2 O molecule and the metal–ruthenium fragment were determined from the energy‐decomposition analysis (EDA) and their electronic structures. The results show that the bonding in the ruthenium(II)/N 2 O adducts 1 – 3 can be interpreted in terms of weak donor–acceptor interactions between the N 2 O molecule and the ruthenium(II) center. The geometrical optimization of the polyoxometalate (POM) adduct 3 indicates a bent Ru–NNO linkage, which effectively enhances donor–acceptor interactions with the quasi π‐symmetry orbital. The mono‐ruthenium(II) substituted Keggin‐type POM adduct 3 is a potential reagent for the activation of the N 2 O molecule because of the strong Ru–NNO bond and the significant RuNN–O π*‐antibonding orbital character relative to adducts 1 and 2 , according to our DFT calculations.