Proximal effects in bimetallic catalysts for olefin polymerization, in cross metathes and in multiblock polymers

Proximity and sterics play a large role in polymn. and polymer chem. In the bimetallic polymn. catalysts where the two metal centers are held on the sam ligand framework, the proximity of the second metal changes reactivity a enhancements of polar group tolerance or isoselecitivity in olefin polymn. are no systems with distal metal centers or in monometallic analogs. In cross metathes chains, high E-stereoregularity and head-to-tail regioregularity are achieved w generation catalysts when there is allylic substitution directing reactivity through polymers, the proximity of incompatible blocks due to a covalent connection system. This frustration can produce interesting and complicated morphologies where thermodn. penalties are expected to minimize the intermaterial dividin demonstrate the power of proximity in directing reactivity, selectivity, and equil. in