Organostannoxane-Supported Palladium Nanoparticles. Highly Efficient Catalysts for Suzuki-Coupling Reactions

Abstract

A phosphine-rich hexameric organostannoxanne, [n-BuSn(O)COOL] 6 (PDrum; L = p-PPh 2 -C 6 H 4 -), has been synthesized by a 6:6 reaction between [n-BuSn(O)OH] n and p-Ph 2 PC 6 H 4 COOH. 119 Sn{ 1 H} NMR of PDrum revealed a single resonance at -481.0 ppm, indicating that it possesses the characteristic drum structure that is well-known among organostannoxanes. Reduction of PdCl 2 with NaBH 4 in the presence of PDrum afforded a palladium nanocomposite, NP-1. HRTEM of NP-1 indicates that the average nanoparticle size is about 3 nm. The latter has been shown to be very effective in mediating Suzuki-coupling reactions involving a number of different substrates. NP-1 can be recycled, and HRTEM analysis of the used catalyst reveals some agglomeration. Treatment of NP-1 with n-hexane and cooling to -25 °C afforded another palladium nanocomposite, NP-2. The latter also is very effective in catalyzing the Suzuki-coupling reaction. HRTEM of NP-2 shows an average nanoparticle size of about 4.3 nm, which remains nearly unchanged even after catalysis. NP-2 is a composite also containing some amounts of SnO 2 .

Multi‐Pyrene Assemblies Supported on Stannoxane Frameworks: Synthesis, Structure and Photophysical Studies

“…More recently, organostannoxane‐supported phosphine ligands have enabled the stabilization of Pd 0 nanoparticles. Such hybrid systems have been effectively utilized as catalysts in various CC bond formation reactions 11c,d. Similarly, OO bond formation mediated by a hexanuclear iron complex supported on a stannoxane core has also been reported 11e…”

Reactions of 4-diphenylphosphino benzoic acid with organotin oxides and -oxy-hydroxide

“…Presence of a characteristic single peak at −481.0 ppm in the 119 Sn{ 1 H} NMR spectra for compound 1 and two signals at −241.1 and −251.2 ppm for compound 2, respectively, confirmed their formation. 3,4,[10][11][12][13][14][15] The 31 P{ 1 H} NMR spectra of 1 and 2 showed singlets at −4.6 ppm and −5.0 ppm (in C 6 D 6 ), respectively. These chemical shifts are comparable to the parent ligand, 4-diphenylphosphino benzoic acid (−4.2 ppm) indicating that the phosphine units in the organostannoxane drum are present in a similar chemical environment as in the parent ligand.…”

“…These chemical shifts are comparable to the parent ligand, 4-diphenylphosphino benzoic acid (−4.2 ppm) indicating that the phosphine units in the organostannoxane drum are present in a similar chemical environment as in the parent ligand. [13][14][15] When we attempted the 1:2 reactions of (n-Bu 3 Sn) 2 O/ (Ph 3 Sn) 2 O with 4-diphenylphosphino benzoic acid instead of the monomeric products, we obtained the 1Dcoordination polymers,…”

“…Such hybrid systems were also shown to be catalytically active for various organic transformations. [13][14][15] However, in these studies we were unable to structurally characterize the parent ligand. With this in mind and also to modulate the nuclearity and structural topology of such phosphinecontaining organostannoxanes, we have carried out the reactions p-diphenylphosphinobenzoic acid (LCOOH) with various organotin precursors which resulted in the isolation of…”

An Efficient Protocol for a Pd(OAc)2-Catalyzed Ligand-Free Suzuki Reaction in Toluene

“…Recently, ligand-free catalytic systems for the Suzuki reaction have been developed because they are simpler and cheaper than ligand-promoted systems [13][14][15][16][17][18][19][20]. As a readily accessible and cheap solvent, toluene is widely applied to the ligand-promoted palladium-catalyzed Suzuki reaction [21][22][23]; however, it is rarely used in ligand-free systems [24]. We thus report a fast and efficient protocol for the Pd(OAc) 2 -catalyzed ligand-free Suzuki reaction of aryl bromides with arylboronic acids in toluene and under air.…”