Palladium(ii) complexes of N,N-diphenylacetamide based thio/selenoethers and flower shaped Pd₁₆S₇and prismatic Pd₁₇Se₁₅nano-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 NaS and NaSe generated in situ, has resulted in thio and selenoether ligands, L1 ((PhNCOCH)S) and L2 ((PhNCOCH)Se), respectively. Reacting these ligands with NaPdCl in ethanol at room temperature resulted in their complexes [Pd(L1/L2)Cl] (C1/C2). P1, L1, L2, C1 and C2 were characterized by H,C{H} and Se{H} 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 PdS (size 26-50 nm) and prismatic PdSe 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.

Organoselenium ligands for heterogeneous and nanocatalytic systems: development and applications

“…71 Other reports also exist in which the composition or phase of a nanomaterial has been found to be dependent on the structure of the ligand used in the single source precursor. [31][32][33][34][35][36][37]…”

“…In this method, preformed metal complexes of organoselenium compounds are used as single source precursors for developing catalytically active and stable nanoparticles of metal selenides. [31][32][33][34][35][36][37]93 The main advantage of this method is that the precursors are thermolysed at moderate temperatures for easy and straightforward synthesis of nanocatalysts. 93 Additional advantages are purity of nanostructures, ease in handling due to moderate operational temperature, reduction in toxicity risks and negligible issues related to air and moisture instability of SSPs.…”

“…94 A variety of organoselenium compounds have been used as building blocks for obtaining many single source precursors. [31][32][33][34][35][36][37] 37) is decomposed at 250°C in the same ionic liquid or in propylene carbonate, platinum clusters (N3) are obtained. It is interesting that the Pt clusters consist of a crystallite Pt core with an amorphous Pt(II)/Se shell and carbene ligand residues.…”

“…Pd 17 Se 15 prismatic nanoparticles (N4) have also been developed by Singh and co-workers by the thermolysis of complex 38 in trioctylphosphine at 280°C (Scheme 6). 32 Using a similar method, nanocatalysts Pd 17 Se 15 and Pd 7 Se 4 (N5 and 6) have also been generated from the selenium-ligated palladium(II) complexes, synthesized by the reactions between Pd (OAc) 2 and dodecyl selenide. 33 In this method, the roles of the structure of the organoselenium ligand and the reaction conditions are crucial.…”

“…[38][39][40] 31 Prismatic nanoparticles of Pd 17 Se 15 (N4), developed via a single source precursor route from complex 38, also catalyse this coupling reaction at 0.5 mol% loading (Scheme 18). 32 Cross-coupled products are obtained in yields of 73-96% in just 3 hours. The highest TOF value is 64 for 4-bromobenzaldehyde with the advantage of recyclability up to 4 catalytic cycles.…”