Influences of steric bulkiness in hydrotris(pyrazolyl)borate ligands on ethylene polymerization reaction

Abstract

Manganese(II) complex catalysts with hydrotris(pyrazolyl)borate ligands have been examined on their catalytic performance in ethylene polymerization and ethylene/1‐hexene copolymerization. The activities of [Mn(L6)(Cl)(NCMe)] (1) and [Mn(L10)(Cl)] (2) activated by Al(i‐Bu)3/[Ph3C][B(C6F5)4] for ethylene polymerization go up to 326 and 11 kg mol (cat−1) h−1, respectively, (L6− = hydrotris(3‐phenyl‐5‐methyl‐1‐pyrazolyl)borate anion, L10− = hydrotris(3‐adamantyl‐5‐isopropyl‐1‐pyrazolyl)borate anion). In particular, for ethylene/1‐hexene copolymerization, complex 1 gives high‐molecular‐weight poly(ethylene‐co‐1‐hexene)s with the highest Mw of 439,000 in manganese olefin polymerization catalyst systems. Moreover, the 1‐hexene incorporation by complex 1 seems more efficient than that by [Mn(L3)(Cl)] (4) (L3− = hydrotris(3‐tertiary butyl‐5‐isopropyl‐1‐pyrazolyl)borate anion). In this work, we demonstrated that the coordination geometry and coordination number are also important factors for ethylene polymerization reaction as well as steric hindrances and ligand frameworks in our manganese(II) catalysts. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5720–5727, 2009

Synthesis and characterization of coordinatively unsaturated nickel(ii) and manganese(ii) alkyl complexes supported by the hydrotris(3-phenyl-5-methylpyrazolyl)borate (TpPh,Me) ligand

“…Alkyl derivatives of Tp Ph,Me MnCl(CH 3 CN) (1) Addition of (trimethylsilyl)methylmagnesium chloride to a diethyl ether solution containing Tp Ph,Me Mn(Cl)(CH 3 CN) (1) 25 resulted in the formation of Tp Ph,Me MnCH 2 Si(Me) 3 (2), isolated as colorless crystals in 70% yield post crystallization from hexane at −40 °C (Scheme 1). An ORTEP diagram shows the molecular structure in Fig.…”

“…Tp Ph,Me MnCl(CH 3 CN) (1), Tp Ph,Me NiCl (4), KTp Ph,Me (7) and Tp Ph,Me CoCl (10) were prepared using literature procedures, and unless otherwise noted, all reagents were acquired from commercial sources. [25][26][27][28] Elemental analyses were performed at the College of Chemistry Microanalytical Laboratory, University of California, Berkeley. X-ray structural determinations were performed at the CHEXRAY facility at UC Berkeley using Bruker SMART 1000 or SMART APEX diffractometers.…”

Synthesis and Structure of a New Bulky Hybrid Scorpionate/Cyclopentadienyl Ligand and its Lithium Complex

“…Sterically crowded homoscorpionates HB(Pz Ad,R ) 3 gained tremen-dous interest several years ago with the HB(3-Ad-5-iPrPz) 3 anion being the most crowded homoscorpionate up to now. This ligand has been studied as tridentate ligand at e. g. copper, [6] iron, [7] manganese, [8] calcium, [9] barium, [10] and ytterbium. [11] Significantly enhanced preparative challenges limited the access to the corresponding isoelectronic C-homoscorpionate [C(Pz Ad,R ) 3 ] À anions and only the magnesium and ytterbium complexes have been investigated so far.…”