d0/f n -Mediated Ring-Opening Ziegler Polymerization (ROZP) and Copolymerization with Mono- and Disubstituted Methylenecyclopropanes. Diverse Mechanisms and a New Chain-Capping Termination Process

• Published in: Organometallics Vol. 23; no. 4; pp. 740 - 754
• Main Authors: Jensen, Tryg R, O'Donnel, James J, Marks, Tobin J
• Format: Journal Article
• Language: English
• Published: American Chemical Society 16.02.2004
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om030407n

The mono- and disubstituted methylenecyclopropane derivatives 2-phenyl-1-methylenecyclopropane (A) and 7-methylenebicyclo[4.1.0]heptane (B) have been successfully implemented in ring-opening Ziegler polymerization. Homogeneous ethylene + 2-phenyl-1-methylenecyclopropane (A) random copolymerizations are mediated efficiently by the single-site catalysts Cp*2ZrMe+B(C6F5)4 -, [Cp*2LuH]2, [Cp*2SmH]2, and [Cp*2YH]2 (Cp* = C5Me5) to produce a copolymer (C) with A enchained in a ring-opened fashion. Single-site coordinative polymerization of 7-methylenebicyclo[4.1.0]heptane (B) proceeds via either ring-opened or ring-unopened pathways. In the presence of Cp*2ZrMe+ MeB(C6F5)3 - at 0 °C, B undergoes polymerization to afford the insoluble, ring-unopened homopolymer D, which was characterized by CPMAS NMR, DSC, elemental analysis, FTIR, TGA, and XRD. The melting point of polymer D lies above its decomposition temperature (>300 °C). Random copolymerizations of B and ethylene mediated by Cp*2ZrMe+MeB(C6F5)3 - at room temperature result in polymer E, a polyethylene capped by a ring-opened B fragment. The formation of B-capped polymer E is a consequence of a new chain transfer mechanism, as evidenced by a linear relationship between M n and [B]-1. The rate constant for insertion of ethylene is ∼25× greater than the rate constant for insertion of monomer B into the metal−alkyl bond. Random copolymers (F) of ring-opened B and ethylene are produced when the catalysts Me2Si(Me4C5)(tBuN)ZrMe2, Me2Si(Me4C5)(tBuN)TiMe2 (activated by either (C6H5)3C+ B(C6F5)4 - or B(C6F5)3), and [Cp*2LuH]2 are employed.