Novel co-catalytic activity of zinc metal with classical initiators for the ring opening polymerisation of norbornene

Zinc metal was shown to considerably increase the activity of the metal(III) chloride salts of ruthenium, iridium and osmium as metathesis initiators for the ROMP of norbornene. The stereochemistry of the polymers formed was determined by 1H and 13C NMR. Formation of the initial carbene species is not via the normally accepted vinyl hydride mechanism. An alternative mechanism involving a metallacyclopentane intermediate is postulated.

Graphical abstractZinc metal was shown to considerably increase the activity of the metal(III) chloride salts of ruthenium, iridium and osmium as metathesis initiators for the ROMP of norbornene. Comparison of this system to a similar one used for the dimerisation of acrylates provides evidence that the hydride mechanism does not occur; an alternative mechanism involving a metallacyclopentane is proposed. Figure optionsDownload full-size imageDownload as PowerPoint slide