Investigation of Steric and Electronic Factors of (Arylsulfonyl)phosphane‐Palladium Catalysts in Ethene Polymerization

Abstract

(Arylsulfonyl)phosphane ligands, o-Ar 2 PC 6 H 4 SO 3 H in which Ar is phenyl (Ph), naphthyl (Np), phenanthryl (Pa), or anthracenyl (An) were prepared. These bulky phosphanes were used to generate phosphanepalladium complexes [(o-Ar 2 -PC 6 H 4 SO 3 )PdMe(pyridine)]. These complexes catalyze eth-

Structure–Activity Relationship of Palladium Phosphanesulfonates: Toward Highly Active Palladium‐Based Polymerization Catalysts

“…[19] However, Gates et al have also shown that replacing a CH 3 fragment by a CF 3 fragment on the diimine leads to a significant activity increase, thus hinting that electron-deficient ligands result in more active catalysts. [20] In a previous study, [13] we demonstrated that catalysts based on phenantryl, naphtyl, and anthracenyl moieties are less active than catalyst 2 a.The difference in phosphane basicities between phenyl, naphtyl, anthracenyl, and phenantryl-based ligands is expected to be small in comparison to the large range of basicities assessed in this study. In our case, it is necessary to clarify whether phosphane s-bonding ability is truly at stake.…”

“…[4i] 2b, [13] 2 c, [13] , and ligand 1 h [14] were already described in the literature, but ligands 1 d, 1 e and 1 g, and catalysts 2 b-lut, 2 d-lut, 2 g-lut, 2 hlut were prepared for the first time for this study. We purposely decided to concentrate our attention to lutidine complexes (or pyridine complexes for catalysts already reported), because we found that DMSO complexes (e.g., 2 h-DMSO) were difficult to isolate in a pure form due to the difficulty of evaporating DMSO.…”

“…[7] Ligand 1 e was also prepared here for the first time, but in line with its electronwithdrawing character, it failed to react with [PdMeClA C H T U N G T R E N N U N G (cod)] or with [PdMe 2 A C H T U N G T R E N N U N G (tmeda)] to afford the corresponding Pd complex. All ligands and catalysts were extensively characterized by multidimensional NMR spectroscopy ( 1 H, 13 C, 31 P), mass spectrometry and elemental analysis. In Scheme 1, ligands are shown under their expected zwitterionic form but, as no JA C H T U N G T R E N N U N G (P,H) coupling was observed, a neutral form could be present.…”

“…1 H, 13 C, 19 F, and 31 P NMR spectra were recorded on a Varian Inova 600 MHz spectrometer or a BrukerUltrashield 300 MHz at ambient temperature except for the polymers, which were analyzed in [D 4 ]1,1,2,2-tetrachloroethane at 115 8C.…”

“…In the past, we also have demonstrated using polyA C H T U N G T R E N N U N G (arylated) phosphanes (Ar = naphtyl, phenantryl and anthracenyl) that molecular weight does not increase when the bulk of the ligand increases. [13] We believe that the failure to correlate our molecular weight data with simple descriptors is likely due to the lack of descriptor to assess steric bulk specifically located in the axial faces of the complex (by opposition to steric bulk of the whole ligand that is captured by the cone angle). In this sense, one can anticipate that complex 2 f, which has one large 2,6-(OMe) 2 C 6 H 3 substituent extending directly above one of the Pd axial position (see the X-ray data of reference.…”