Methylaluminoxane as a novel catalyst and cocatalyst for ring-opening metathesis polymerisation of norbornene

Abstract Methylaluminoxane (MAO) alone acts as a weak catalyst for the ring-opening metathesis polymerisation of norbornene, thereby providing good evidence that some transient [Al]C metallacarbenes are formed and propagate the reaction. A novel general mechanism of initiation involving generation of metallacyclopentanes, followed by ring contraction to metallacyclobutanes, is proposed. Methylaluminoxane is also a very effective cocatalyst for Mo and W chlorides, and especially for non-ionic carbonyl compounds of these two metals. Remarkably cis / trans highly stereo-blocky polymers are obtained which for the first time show clear resolution ( m / r ) on some of the 13 C NMR lines.