Neutral Imino-Methyl Benzenesulfonate-Ligated Pd(II) Complexes and Implications in Ethylene Polymerization

Abstract

A reaction between sodium 2-formylbenzenesulfonate and aniline revealed the near-quantitative (91%) formation of sodium-2-((phenylimino)methyl)benzenesulfonate L1 . The identity of L1 was unambiguously ascertained using spectroscopic and analytical methods. The scope of this methodology was widened and various electron-donating amines were treated with sodium 2-formylbenzenesulfonate, and a small library of 6 imine ligands L2–L6 was generated. When L2 was treated with [(COD)PdMeCl], instead of the anticipated [ L2 PdMe(DMSO)] complex, the formation of [(DMSO) 2 Pd 2 Cl 2 Me 2 ] Pd-Dim was observed. Nevertheless, the desired imino-methyl benzenesulfonate-ligated palladium complex [ L2 PdMe(Lu)] C1 was obtained by in situ abstraction of chloride and addition of bulky 2,6-lutidine as the donor group. The observation of characteristic Pd–Me protons at 0.06 ppm and the corresponding carbon at −8.1 ppm indicated the formation of C1 . These 1D NMR observations were corroborated by 2D C–H correlation spectra and mass analysis, and the existence of C1 was unambiguously ascertained. Along the same lines, L4 and L5 were treated with a palladium precursor to produce [ L4/5 PdMe(Lu)]-type complexes C2–C3 in 55–84% yield, and their identity was established by using a combination of spectroscopic tools, analytical methods, and single-crystal X-ray diffraction. The synthetic utility of C1–C3 has been demonstrated by utilizing these complexes in the insertion polymerization of ethylene to polyethylene.

Aryl sulfonate anion stabilized aromatic triangular cation [Pd3]+: syntheses, structures and properties

“…The unique allmetal aromaticity and excellent stability endow such threemembered palladium cores with excellent molecular stability and Lewis alkalinity, which has brought them much attention in theoretical chemistry, [8][9][10][11] coordination chemistry, 12 catalytic reactions [13][14][15][16][17][18][19][20][21][22] and nanomaterials. 23 Compared with the usual negative ions like SbF 6 − , PF 6 − , BF 4 − and CF 3 COO − , from the perspective of electronic factors of ion pairs for organometallic complexes, aryl sulfonate anions (ArSO 3 − ) were recognized as much weaker s-donors and usually present milder coordination abilities with transition metals, [24][25][26] which could potentially bring distinctive structural and characteristic properties for aromatic tripalladium frameworks. As the foundation of this work, the Zwitterionic analogue reected high stability, catalytic activity and stereoselectivity in the selective reduction of alkynes.…”

“…Compared with the usual negative ions like SbF 6 − , PF 6 − , BF 4 − and CF 3 COO − , from the perspective of electronic factors of ion pairs for organometallic complexes, aryl sulfonate anions (ArSO 3 − ) were recognized as much weaker σ-donors and usually present milder coordination abilities with transition metals, 24–26 which could potentially bring distinctive structural and characteristic properties for aromatic tri-palladium frameworks. As the foundation of this work, the Zwitterionic analogue reflected high stability, catalytic activity and stereoselectivity in the selective reduction of alkynes.…”