Palladium(ii) complexes of N,N-diphenylacetamide based thio/selenoethers and flower shaped Pd16S7 and prismatic Pd17Se15 nano-particles tailored as catalysts for C–C and C–O coupling

Abstract

2-Bromo-N,N-diphenylacetamide (P1) prepared by reacting diphenylamine with α-bromoacetyl bromide, on treatment with Na₂S and Na₂Se generated in situ, has resulted in thio and selenoether ligands, L1 ((Ph₂NCOCH₂)₂S) and L2 ((Ph₂NCOCH₂)₂Se), respectively. Reacting these ligands with Na₂PdCl₄ in ethanol at room temperature resulted in their complexes [Pd(L1/L2)₂Cl₂] (C1/C2). P1, L1, L2, C1 and C2 were characterized by ¹H, ¹³C{¹H} and ⁷⁷Se{¹H} NMR spectroscopy, IR spectroscopy and High resolution mass spectrometry (HR-MS). Single crystal structures of all the five compounds were determined by X-ray diffraction. In both C1 and C2 the geometry of Pd is nearly square planar. Flower shaped Pd₁₆S₇ (size 26–50 nm) and prismatic Pd₁₇Se₁₅ NPs (size 20–55 nm) were synthesized by a single source precursor route (thermolysis at ∼280 °C in trioctylphosphine) from air and moisture insensitive C1 and C2, respectively. These shapes of the two nanophases were unknown hitherto. They were characterized by powder X-ray diffraction (PXRD), SEM-EDX and HR-TEM and found to show good catalytic activity for Suzuki–Miyaura (Pd loading 0.5 mol%; yield up to 96%) and C–O (Pd loading 0.5 mol%; yield up to 96%) coupling reactions (at 100 °C) of aryl bromides with phenylboronic acid and phenol, respectively. The complexes C1 and C2 were found very efficient for Suzuki–Miyaura and C–O coupling as revealed by their optimum loading of 0.0001–0.01 and 0.1 mol% of Pd, respectively, for the two reactions. The reuse of the complexes or NPs as a catalyst is demonstrated.