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

Abstract

A series of chalcogenoether ligands RE(CH 2 ) n NMe 2 (1) [E = Se or Te; R = Ph, o-tol (o-tol = ortho-tolyl), Mes (Mes = 2,4,6trimethylphenyl); n = 2 or 3] and their palladium complexes [PdX 2 {RE(CH 2 ) n NMe 2 }] m [X = Cl (2) or OAc (3); m = 1, 2] were synthesized. Complexes [PdCl 2 (RECH 2 CH 2 NMe 2 )] [R/E = Ph/Se (2a), Mes/Se (2b), Mes/Te (2c)] were isolated as monomers. Complexes [PdCl 2 (RECH 2 CH 2 CH 2 NMe 2 )] 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 [a]397 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.

Coordination Polymers of Palladium Bridged by Carboxylate and Dimethylaminoalkylselenolate Ligands

“…The connectivity shows that all the four protons of “CH 2 CH 2 ” group are correlated. A similar complex 1 H NMR pattern was reported for selenoether complexes [PdCl 2 (RSeCH 2 CH 2 NMe 2 )] n . The sharp singlet at δ 212 ppm ([D 6 ]acetone) in the 77 Se NMR spectrum (Figure S9, Supporting Information) is the signature of a single product with four magnetically equivalent selenium atoms.…”

“…Sulfur‐ or selenium‐based ligands may provide additional stability to PdNPs, which are believed to be active species in catalytic reactions . Accordingly, we have developed chalcogenolato‐bridged palladium acetate complexes as catalysts for C−C coupling reactions . The complexes [Pd(OAc)(ECH 2 CH 2 NMe 2 )] 3 and [Pd(OAc)(ECH 2 CH 2 CH 2 NMe 2 )] 2 (E=S or Se) showed promising catalytic activities.…”

Supramolecular Macrocyclic Pd(II) and Pt(II) Squares and Rectangles with Aryldithiolate Ligands and their Excellent Catalytic Activity in Suzuki C–C Coupling Reaction

“…To assess the suitability of macrocyclic palladium complexes as homogeneous catalyst in C–C coupling reaction, the activity of these complexes is examined in Suzuki coupling reactions. On the basis of our recent experiments on optimization study of reaction conditions in Suzuki coupling reactions using palladium chalcogenolate/chalcogeno ether complex as catalysts, the solvent dioxane, base K 2 CO 3 and temperature 100 °C were used as reaction conditions . It is evident from Table that the complexes 3a , 4a , and 5a efficiently catalyzed the coupling reaction of both electron-rich and -poor aryl bromides with phenylboronic acids, with more than 90% isolated yield.…”

Reactivity of 4‐Pyridyltellurolate with Pd(II)/Pt(II) Complexes

“…The chalcogen complexes of platinum group metals find extensive applications in catalysis and material science . The Pd(II) complexes of sulfur and selenium based chalcogenoether and chalcogenolate ligands have emerged as highly efficient homogeneous catalysts for C−C bond forming reactions such as Suzuki and Heck reactions. The thiolates/selenolates of M(II) (M=Pd, Pt) have been used as molecular precursors for the synthesis of metal/metal‐enriched chalcogenides such as ME, Pd 4 E, (E=S, Se), Pd 17 Se 15 , etc which have largely been used as catalysts, semiconducting materials and electrodes.…”