Influence of Noncovalent Interaction on the Nucleophilicity and Electrophilicity of Metal Centers in [M II (S 2 CNEt 2 ) 2 ] (M = Ni, Pd, Pt).

A systematic theoretical study was performed on the electrophilic and nucleophilic properties of Group 10 square-planar metal compounds [M ^II (S ₂ CNEt ₂ ) ₂ ] (M = Ni 1 , Pd 2 , and Pt 3 ) and their complexes. The nucleophilic metal center and coordinated sulfur atom in [M(S ₂ CNEt ₂ ) 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 = NH ₃ , NHCH ₂ , pyridine) due to the push-pull mechanism. The N···Ni semicoordination bond exerts a push effect on the d _{z ²} 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.