Palladium(ii) complexes of 2,2′-tellurobis(N,N-diphenyl acetamide): efficient catalysts for Suzuki–Miyaura coupling at room temperature under air

Abstract

Three complexes, [Pd(L2)₂Br₂] (C1), [(L2)PdCl(μ-Cl)₂PdCl(L2)] (C2), and [Pd(L2)PPh₃Cl₂](C3) of a tellurium ligand, 2,2′-tellurobis(N,N-diphenylacetamide) ((Ph₂NCOCH₂)₂Te = L2), reported here catalyze Suzuki–Miyaura coupling efficiently at room temperature under aerobic conditions, and the optimum loading of the catalyst is 0.001 mol% of Pd. Oxidative addition of elemental tellurium to 2-bromo-N,N-diphenylacetamide results in bis(N,N-diphenylamidomethyl)tellurium(IV) dibromide ((Ph₂NCOCH₂)₂TeBr₂) (L1). The reduction of L1 with aqueous bisulfite results in (Ph₂NCOCH₂)₂Te(= L2). The complexes C1 and C2 were obtained by the reactions of L1 and L2 with Na₂PdCl₄ at room temperature in dichloromethane and ethanol, respectively. The complex C2 on reaction with triphenylphosphine results in C3. L1, L2, C1, C2, and C3 were characterized by HR-MS, ¹H, ¹³C{¹H} and ¹²⁵Te{¹H} NMR and IR spectra. The single crystal structures of all these compounds were determined by X-ray diffraction. The geometry of Pd in all the complexes, C1–C3, is nearly square planar. The scope of C1–C3 for catalysis of Suzuki–Miyaura coupling is reported.