Nickel Chelate Complexes of 2-Alkylphenylphosphanylphenolates: Synthesis, Structural Investigation and Use in Ethylene Polymerization

Abstract

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∩O)] (3). Addition of a second equivalent of 1 or 2 affords (RR) and (SS) diastereoisomers of cis‐bis(P∩O‐chelates) 4a–c (R = Ph, Me, iPr) or the unsymmetrical cis‐bis(P∩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∩O) complexes 3, however, are too stable to be active in this process. The crystal and molecular structure of 3c and 4c are described.

Nickel Catalyzed Copolymerization of Ethylene and Alkyl Acrylates

“…Here we report a novel class of Ni-based SHOP catalysts, the preparation of which is shown in Scheme where the reaction of Ni­(cod) 2 and o -bis­(aryl)­phosphinophenol 1a – 1i gave neutral σ, π-cyclooct-4-enyl Ni­(II) complexes 2a – 2i almost quantitatively . We found that the complexes can copolymerize ethylene and alkyl acrylates with high activity to give highly linear copolymers with high molecular weight (Scheme ).…”

o‐Hydroxyarylphosphanes: Strategies for Syntheses of Configurationally Stable, Electronically and Sterically Tunable Ambiphiles with Multiple Applications

“…[77,79] The silyl ethers can also be used for O-lithiation, O-acylation, [97b] reactions with ClER n reagents, with transition metal halides and the preparation of (P,O)-nickel ethylene polymerization catalysts. [98] The o-lithio-phenolates and -naphtholates 26 OM (M=Li or Na; R n = H and 5,6-C 4 H 4 ) were also applied to stereospezific syntheses of P-asymmetric o-hydroxyarylphosphanes, using the Jugé-Stephan route. Reaction in THF (À 20 °C to rt) with the (2S,4R,5S)-(-)-1,3,2-oxazaphospholidine 32, obtained from PhP(NEt 2 ) 2 , (+)-ephedrine and BH 3 •THF, [99] provides the PÀ O ring-opening product (R P )-33 with retention of configuration (Scheme 9).…”

“…By reaction with MeOH in the absence of traces of acids and moisture (best in the presence of Et 3 N to avoid side products by H + ‐catalyzed Arbuzov reaction) the NR 2 groups of 29 are replaced by OMe groups and allow reduction by LiAlH 4 to PH‐functional o ‐phosphanylphenols [77,79] . The silyl ethers can also be used for O‐lithiation, O‐acylation, [97b] reactions with ClER n reagents, with transition metal halides and the preparation of ( P , O )‐nickel ethylene polymerization catalysts [98] …”