Synthesis and Reactivity of Palladium(II) Alkyl Complexes that Contain Phosphine-cyclopentanesulfonate Ligands

Abstract

The synthesis of the phosphine-cyclopentanesulfonate pro-ligands Li/K[2-PPh2-cyclopentanesulfonate] (Li/K[2a]), Li/K[2-P(2-OMe-Ph)2-cyclopentanesulfonate] (Li/K[2b]), and H[2b], and the corresponding Pd(II) alkyl complexes (κ2-P,O-2a)PdMe(pyridine) (3a) and (κ2-P,O-2b)PdMe(pyridine) (3b) is described. The sulfonate-bridged base-free dimer {(2b)PdMe}2 (4b) was synthesized by abstraction of pyridine from 3b using B(C6F5)3. The borane-coordinated base-free dimer [{2b·B(C6F5)3}PdMe]2 (5b), in which B(C6F5)3 binds to a sulfonate oxygen, was prepared by addition of 1 equiv of B(C6F5)3 per Pd to 4b or addition of 2 equiv of B(C6F5)3 to 3b. Compounds 3b, 4b, and 5b polymerize ethylene with low activity (up to 210 kg mol–1 h–1 at 250 psi and 80 °C) to linear polyethylene (Mn = 1950–5250 Da) with predominantly internal olefin placements. 3b and 4b copolymerize ethylene with methyl acrylate to linear copolymers that contain up to 11.7 mol % methyl acrylate, which is incorporated as −CH2CH(CO2Me)CH2– (80%) in-chain u...