<i>Ortho</i>-Phosphinobenzenesulfonate: A Superb Ligand for Palladium-Catalyzed Coordination–Insertion Copolymerization of Polar Vinyl Monomers
Bibliographic record
Abstract
Ligands, Lewis bases that coordinate to the metal center in a complex, can completely change the catalytic behavior of the metal center. In this Account, we summarize new reactions enabled by a single class of ligands, phosphine-sulfonates (ortho-phosphinobenzenesulfonates). Using their palladium complexes, we have developed four unusual reactions, and three of these have produced novel types of polymers. In one case, we have produced linear high-molecular weight polyethylene, a type of polymer that group 10 metal catalysts do not typically produce. Secondly, complexes using these ligands catalyzed the formation of linear poly(ethylene-co-polar vinyl monomers). Before the use of phosphine-sulfonate catalysts, researchers could only produce ethylene/polar monomer copolymers that have different branched structures rather than linear ones, depending on whether the polymers were produced by a radical polymerization or a group 10 metal catalyzed coordination polymerization. Thirdly, these phosphine-sulfonate catalysts produced nonalternating linear poly(ethylene-co-carbon monoxide). Radical polymerization gives ethylene-rich branched ethylene/CO copolymers copolymers. Prior to the use of phosphine-sulfonates, all of the metal catalyzed processes gave completely alternating ethylene/carbon monoxide copolymers. Finally, we produced poly(polar vinyl monomer-alt-carbon monoxide), a copolymerization of common polar monomers with carbon monoxide that had not been previously reported. Although researchers have often used symmetrical bidentate ligands such as diimines for the polymerization catalysis, phosphine-sulfonates are unsymmetrical, containing two nonequivalent donor units, a neutral phosphine, and an anionic sulfonate. We discuss the features that make this ligand unique. In order to understand all of the new reactions facilitated by this special ligand, we discuss both the steric effect of the bulky phosphines and electronic effects. We provide a unified interpretation of the unique reactivity by considering of the net charge and the enhanced back donation in the phosphine-sulfonate complexes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".