Sterically Demanding, Sulfonated, Triarylphosphines: Application to Palladium-Catalyzed Cross-Coupling, Steric and Electronic Properties, and Coordination Chemistry

Abstract

Tri(2,4-dimethyl-5-sulfonatophenyl)phosphine trisodium (TXPTS·Na3) and tri(4-methoxy-2-methyl-5-sulfonatophenyl)phosphine trisodium (TMAPTS·Na3) both provide more active catalysts for Suzuki and Sonogashira couplings of aryl bromides in aqueous solvents than tri(3-sulfonatophenyl)phosphine trisodium (TPPTS·Na3). In the Heck coupling, TXPTS·Na3 provides the most effective catalyst system. Cone angles determined from DFT-optimized structures show that both TXPTS·Na3 (206°) and TMAPTS·Na3 (208°) are significantly larger than TPPTS·Na3 (165°). The identity of the counterion had a significant effect on the calculated cone angles for these ligands. The electronic properties of these ligands determined by the CO stretching frequencies of trans-RhL2(Cl)CO complexes were identical, although calculated electronic parameters suggest subtle differences between these ligands. Similar to TPPTS·Na3, both TXPTS·Na3 and TMAPTS·Na3 react with Pd(OAc)2 in aqueous solvents to give LnPd0 complexes and the corresponding phosphine oxide. The reduction of palladium(II) by TXPTS·Na3 is significantly slower than is seen with TMAPTS·Na3 or TPPTS·Na3 at room temperature. Evidence of palladacycle complexes derived from TXPTS·Na3 and TMAPTS·Na3 by activation of an ortho-methyl substituent was also observed in ligand coordination studies and under catalytic reaction conditions.

Palladium-containing hypercrosslinked polystyrene as an easy to prepare catalyst for Suzuki reaction in water and organic solvents

“…The reaction has been studied extensively in homogeneous conditions using a variety of palladium-containing complexes as the catalyst [4,5]. Homogeneous catalysts, however, suffer from the problems of separating the catalyst from the reaction mixture and catalyst recycling.…”

Triple Function of 4‐Mercaptophenylacetic Acid Promotes One‐Pot Multiple Peptide Ligation

“…In the presence of only water, the activity of the Pd/TPPTS complex was retained even after stirring for 10 min. [10] Furthermore,t he replacement of MPAA with TPPTS changed the electron density of palladium complexes,w hich could hamper the oxidative addition of Alloc groups.I ti snotable that during removal of the Alloc [a] The conversion yields were calculated from peak areas analyzed by HPLC (shown in Figure S4). Under these conditions,the palladium complex was completely inactivated after stirring for 10 min.…”

Basic Research Needs: Catalysis for Energy

“…In a number of examples, calculations are used in refining these structures. For example, calculations can be used to determine orientations of ligands around metal centers and to predict properties such as cone angles and binding energies that can be used to interpret experimental results for complex reactions such as carbon-carbon coupling reactions (Moore et al 2007). There is little information about structures of energy feedstocks in catalytic processes to guide the development of models for these systems.…”