2‐Phosphanylphenolate Nickel Catalysts for the Polymerization of Ethylene

Abstract

The previously unknown methallylnickel 2-diorganophosphanylphenolates (R=Ph, cHex) were synthesized and found to catalyze the polymerization of ethylene. To explore the potential for ligand-tuning, a variety of P-alkyl- and P-phenyl-2-phosphanylphenols was synthesized and allowed to react with [Ni(cod)(2)] (cod=1,5-cyclooctadiene) or with NiBr(2).DME and NaH. The complexes formed in situ with [Ni(cod)(2)] are generally active as ethylene polymerization catalysts with all the ligands tested, whereas the latter systems are inactive when 2-dialkylphosphanylphenols are applied. M(w) values, ranging from about 1000 to about 100000 g mol(-1), increase for various R(2)P groups in the order R=Ph<Et approximately tBu<iPr<cHex, while aryloxy substituents usually diminish the molecular weights. Increasing basicity of P- or aryloxy substituents usually leads to increasing turnover numbers. The polymers are high density polyethylene (HDPE) with low methyl and sometimes low long-chain branching. Investigation of the influence of the solvent shows that the catalysts are stabilized by some oxygen-containing Lewis bases as well as by olefins. The catalysts are tolerant to water, in particular the 2-dicyclohexylphosphanylphenolate nickel catalyst, which in THF-water (1:1) gives HDPE with M(w)=39000, M(n)=14500 g mol(-1). Additives of tetrahydrothiophene or pyridine do not inhibit the catalyst, but decrease the reaction rate and the molecular weight of the polymers.

Stereoselective Synthesis of N‐Glycosyl Amino Acids by Traceless Staudinger Ligation of Unprotected Glycosyl Azides

“…[7] It is stable to air at room temperature for weeks and can be handled with no special precautions. Acylation followed by silica gel filtration affords the ligation agents 4, which can be used without further purification.…”

“…Thus, we replaced phosphanes 1 with the corresponding monofluoro derivatives 4 (Scheme 4), which could be obtained in high yields from the known phosphane 7 [7] by reaction with the appropriate amino acids and condensing agents (Scheme 4). The functionalized phosphanes 4a-e were synthesized to examine the Staudinger ligation of the aspartic and glutamic acid side-chains (4a and 4b, respectively) as well as the reactions of simple α-and β-amino acids such as β-alanine 4c, glycine 4d and proline 4e.…”

Resolving Conformation Dichotomy for Y‐ and T‐Shaped Three‐Coordinate NiI Carbonyl Complexes with Relativistic DFT Analysis of EPR Fingerprints

“…[1,2] For instance, nickelexchanged zeolites play an important role in studying the mechanistic aspects of selective catalytic reduction of NO x [2] or selective hydrogenation of nitro aromatic compounds. [3] Phosphanylphenolate nickel complexes are active in olefin polymerization, [4] whereas the methanogenesis cycle is catalyzed by methylcoenzyme M (methyl-CoM) reductase with the cofactor F 430 comprising Ni I hydrocorphinoid. [5] Ni I -carbonyls of biologically relevant complexes can mimic the activity of acetylcoenzyme A synthases (acetyl-CoA) [6] or dihydrogen oxidation by hydrogenases.…”

PH‐functional o‐phosphinophenols— synthesis via methoxymethylethers and screening tests for Ni‐catalyzed ethylene polymerization

“…Selected bond lengths (Å) and angles ( • ): P C(1) 1.8347(17), P P#1 2.2253(6); C(1) P P#1 104.31(6), C(1) P P#2 100.86(6), P#1 P P#2 85.134(13), P C(1) C(2) 124.99(12), P C(1) C(6) 116.79 (13); symmetry transformations used to generate equivalent atoms: #1 −y + and Ni(COD) 2 (COD 1,5-cyclooctadiene) or other related isolated complexes catalyze the polymerization or oligomerization of ethylene [3,4]. Ligand tuning revealed that the polymer chain length increases for various PR 2 groups in the order Ph 2 P < PhtBuP ≈ PhiPrP < Et 2 P < tBu 2 P < iPr 2 P < cHex 2 P. This is accounted for by an increase of the chain lengths with the basicity of the phosphino groups, superimposed upon a sterically induced decrease in the case of α-branched alkyl groups [3a], and raises the question of the effect of primary and secondary phosphino groups.…”

“…P-Tertiary 2-phosphinophenols have found considerable interest as ligands in transition metal complexes [1,2], and organonickel phosphinophenolate chelate complexes proved to be efficient moisturetolerant polymerization or oligomerization catalysts [1, 3,4]. P-Tertiary 2-phosphinophenol ethers became familiar by the formation of hemilabile P ∩ O-chelate complexes [5] and the use of suitable asymmetric derivatives in highly enantioselective Rh-catalyzed hydrogenation reactions [6].…”