Influence of Noncovalent Interaction on the Nucleophilicity and Electrophilicity of Metal Centers in [MII(S2CNEt2)2] (M = Ni, Pd, Pt)

Abstract

A systematic theoretical study was performed on the electrophilic and nucleophilic properties of Group 10 square-planar metal compounds [M^II(S₂CNEt₂)₂] (M = Ni 1, Pd 2, and Pt 3) and their complexes. The nucleophilic metal center and coordinated sulfur atom in [M(S₂CNEt₂)₂] facilitate the formation of metal-involving and conventional noncovalent bonds. The presence a heavier metal center results in a more negative electrostatic potential and a larger nucleophilicity, which in turn leads to the formation of stronger metal-involving noncovalent bonds than those formed by a lighter metal center. The Ni^II center was observed to display electrophilic–nucleophilic dualism with regard to noncovalent interactions, forming both a metal-involving halogen bond (Ni···I) with iodine chloride (ICl) and a semicoordination bond (Ni···N) with N-bases. The nucleophilicity and electrophilicity of the Ni^II center are enhanced in the ternary complexes LB···1···XCl (X = H, I; LB = NH₃, NHCH₂, pyridine) due to the push–pull mechanism. The N···Ni semicoordination bond exerts a push effect on the d_z² orbital of the Ni^II center, while the Ni···X noncovalent bond provides a symbiotic pull effect on this orbital. Furthermore, the formation of metal-involving noncovalent bonds may enhance the electrophilic ability of the Pd^II and Pt^II center, resulting in the formation of stable ternary complexes Py···2/3···XCl (X = H, I), which are characterized by M···N and M···X interactions.