Selective extraction of Pd(ii) by p-tert-butylcalix[4]arenedicarboxylic acid

Abstract

p-tert-Butylcalix[4]arenedicarboxylic acid, in which two distal hydroxy groups of p-tert-butylcalix[4]arene are replaced with carboxy groups, shows extraction selectivity toward Pd2+ ions by the formation of a 2 : 2 (M/L) complex.

Spatial Anion Control on Palladium for Mild C–H Arylation of Arenes

“…Structural factors resulting from the bent spatial orientation of the two constrained carboxylates, such as distortion of the bis(anion) backbone and deviation from optimal coordination bond lengths and angles, could contribute to the strain in the ground state of L a Pd, which is relieved in the CMD transition state (Figure 3c). The spatial anion control imposed by L a 2− is further supported by the uncommon coordination of the two κ 1 -carboxylates and two nitriles in L a Pd(CH 3 CN) 2 (Figure 4, Table S2), 69 with the geometrical parameters, O3−Pd1−O4, 44.55(4)°, Pd1−O3, 1.9801(10) Å, and Pd1−O4, 3.1839 (14) Å, being similar to those in TS CMD , 45.9°, 2.06 Å, and 3.12 Å, respectively (Figure 3a).…”

Extraction of Pd(ii) and Pt(ii) from aqueous hydrochloric acid with 1,3-diaminocalix[4]arene: switching of the extraction selectivity by using different extraction modes

“…We applied the novel calixarenes as metal extractants and succeeded in the selective extraction of Yb(III) from lanthanoid ions 39 and Zr(IV) over Hf(IV) 40 using calix [4]arenediphosphonic acid, and that of Pd(II) from PGMs using calix [4]arenedicarboxylic acid. 41 One of the origin for the high metal discrimination abilities of these extractants is their rigid coordination environments that are realized by the coordinating groups directly introduced on the calix skeleton. In this study, we have investigated the PGM extraction ability of 1,3-diaminocalixarene (2), 36 expecting the direct coordination of the amino groups to the so metals and the formation of ion pairs with chloro complexes under acidic conditions.…”

Introduction to Spatial Anion Control for Direct C–H Arylation

“…Simple carboxylates favor the formation of  2 or bridged complexes in the presence of neutral weak donors like nitriles, with a rare example being reported of a crystallographically characterized Pd(II) bis( 1 -carboxylate) bis(acetonitrile) complex, which is stabilized by intramolecular hydrogen bonds (Figure 2). 99 With L a 2-, a palladium(II) com-plex with uncommon cis-binding of the two  1 -carboxylates (in the presence of nitriles as the neutral donors) was obtained, which features geometrical parameters of carboxylate coordination similar to those required in the CMD transition state (Figure 2). 35 This demonstrates that spatial anion control can be of use to impart uncommon coordination geometries with relevance to catalysis.…”