260251-74-9

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• 185509-29-9 (2-hydroxy-5-methylphenyl)diphenylphosphine 

Relevant academic research and scientific papers

O-Acylated 2-Phosphanylphenol Derivatives - Useful ligands in the Nickel- Catalyzed polymerization of ethylene

The title ligands were prepared by O-acylation of 2-di- phenylphosphanyl-4-methylphenol (1) or directly by double lithiation of 2-bromo-4-methylphenol and stepwise coupling with ClPPh2 and ClP(O)Ph2 or RC(O))C1 (R = Me, tBu, Ph, 4-MeOC6H 4) to afford diphenylphosphinate 2 and carboxylic esters 3a-d. X-ray crystal structure analyses of 3b-d show conformations in which the P-phenyl substituents are rotated away from the ester group and the C(O)O π planes are nearly perpendicular to the phenol ring π plane. O-Acylated phosphanylphenols 2 and 3a-d form highly active catalysts with Ni(l,5-cod) 2 (as does 1) for polymerization of ethylene, whereas phosphanylphenyl ethers do not give catalysts under the same conditions. The reason is the cleavage of the O-acyl bond upon heating with nickel(O) precursor compounds in the presence of ethylene. The precursors are P- coordinated Ni 0 complexes, which are formed at room temperature, such as 4d obtained from 3d and Ni(cod)2 in a 2:1(molar ratio), and characterized by multinuclear NMR spectroscopy. Upon heating in the presence of ethylene, the pre-catalysts are activated. Catalysts2Ni and 3a-d Ni convert ethylene nearly quantitatively, 2Ni slowly, and 3a-dNi rapidly, into linear polyethylene with vinyl and methyl end groups, and in the latter case, C(O)R end groups are also detectable. This proves insertion of Ni0into the O-C(O)R bond of 3a-d ligands for formation of the primary catalyst. Termination of the first chain growing cycle by β-hydride elimination changes the mechanism to the phosphanylphenolate- NiH initiated polymerization providing the main body of the polymer. A small retardation in the ethylene consumption rate with 3a-dNi, catalysts relative to that observed for lNi and stabilization of the catalyst, which gives rise to reproducibly high ethylene conversion, is observed.

Nickel chelate complexes of 2-alkylphenylphosphanylphenolates: Synthesis, structural investigation and use in ethylene polymerization

2-Diphenylphosphanyl- and 2-alkylphenylphosphanyl-4-methylphenols 1 or their silyl ethers 2 and equimolar amounts of nickelocene react in benzene preferably to give orange-brown diamagnetic cyclopentadienylnickel chelate complexes [η-CpNi(P(intersection set)O)] (3). Addition of a second equivalent of 1 or 2 affords (RR) and (SS) diastereoisomers of cis- bis(P(intersection set)O-chelates) 4a-c (R = Ph, Me, iPr) or the unsymmetrical cis-bis(P(intersection set)O-chelate) 5, whereas with bulkier substituted derivatives 1d or 2d (R = tBu) the second step is hindered or retarded. The reactivity of 1d remains high towards nickel salts in polar solvents, but in contrast to 1a-c, yielding 4, a sparingly soluble green trans-bis(P-O-chelate) nickel complex 6d is formed. Complexes formed in situ from 1 or 2 and Ni(COD)2 in toluene catalyze the polymerization of ethylene. The cyclopentadienyl (P(intersection set)O) complexes 3, however, are too stable to be active in this process. The crystal and molecular structure of 3c and 4c are described.