New monodentate and bidentate silylene ligands by DFT.

Considering the importance of silylene ligands in transition metal‐mediated catalytic reactions, we have scrutinized eight novel monodentate (1–4) and bidentate (1′‐4′) derivatives of 2,5‐diX‐cyclopentasilylene‐2,4‐dienes (X = NH2, OH, PH2, and SH), at M06/6‐311++G** level of theory. To probe the complexation ability of our scrutinized silylene ligands with Rh atom (1Rh‐4Rh and 1′Rh‐4′Rh, respectively), thermodynamic and structural parameters such as complexation energy (ΔECom), singlet‐triplet energy gap (ΔEs‐t), bond length, along with NBO and atoms in molecules analyses are provided. In going from less electron donating groups (EDGs) to more EDGs (NH2 > OH > PH2 > SH), the σ‐donor strength and ligand flexibility increase. Structures 1 and 1′ turn out as the most nucleophilic species for showing the highest nucleophilicity (N = 5.47 and 5.40 eV, respectively). Furthermore, they exhibit the highest proton affinity values (PA = 271.46 and 271.23 kcal/mol, respectively). The results indicate that bidentate coordination mode of silylene leads to a stronger Si‐Rh complex. The overall orders of σ‐donation ability for monodentate and bidentate silylene ligands are 1 > 2 > 3 > 4 and 1′ > 2′ > 3′ > 4′, respectively. [ABSTRACT FROM AUTHOR]