| Abstract: | Hydrogen has been shown to be a true chain-transfer agent with some organometallic olefin polymerization catalysts. However, the Mayo equation for chain transfer in free-radical polymerization does not fit quantitative data from organometallic catalysts. There appear to be two reasons for the lack of fit. First, the Mayo equation considers the competition between hydrogen and olefin for the growing chain but does not account for their competitive absorption on the catalyst (coordination with vacant orbitals on the transition metal). Second, some organometallic catalysts gradually absorb hydrogen irreversibly to give a new catalyst species of altered behavior. |
