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 = NH 2 , OH, PH 2 , and SH), at M06/6‐311++G** level of theory. To probe the complexation ability of our scrutinized silylene ligands with Rh atom ( 1 Rh ‐ 4 Rh and 1 ′ Rh ‐ 4 ′ Rh , respectively), thermodynamic and structural parameters such as complexation energy (Δ E Com ), singlet‐triplet energy gap (Δ E s‐t ), bond length, along with NBO and atoms in molecules analyses are provided. In going from less electron donating groups (EDGs) to more EDGs (NH 2 > OH > PH 2 > 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.