Structural Variation in [PdX2{RE(CH2)nNMe2}] (E = Se, Te; X = Cl, OAc) Complexes: Experimental Results, Computational Analysis, and Catalytic Activity in Suzuki Coupling Reactions

A series of chalcogenoether ligands RE(CH2)(n)NMe2 (1) [E = Se or Te; R = Ph, o-tol (o-tol = ortho-tolyl), Mes (Mes = 2,4,6-trimethylphenyl); n = 2 or 3] and their palladium complexes [PdX2{RE(CH2)(n)NMe2}](m) [X = Cl (2) or OAc (3); m = 1, 2] were synthesized. Complexes [PdCl2(RECH2CH2NMe2)] [R/E = Ph/Se (2a), Mes/Se (2b), Mes/Te (2c)] were isolated as monomers. Complexes [PdCl2(RECH2CH2CH2NMe2)](m) [R/E = Ph/Se (2d), Ph/Te (2e), o-tol/Te (2f)] exist in one monomeric and two dimeric forms in solution; their ratio depends on E and R as revealed by NMR spectroscopic data. Crystal structures of monomeric 2a, 2b, 3b, 2d, 2f, and dimeric 2e were established. Compounds 2a, 2d, 2e, and 2f were also investigated by means of density functional theory (DFT)-based quantum chemical calculations to understand structural variation. The complexes that contained acetate or chalcogenoether ligands with n = 3 showed higher catalytic activity than other derivatives in Suzuki C-C cross-coupling reactions.