Even at a ratio of Al:Zr = 1000:1, formation of 2b and other products does not proceed to completion with 6,4 and 7,5 present in equal amounts at 0.5 mol% of total Al (a 10-fold excess of activator over added Zr). Only about 42 mol% of SBIZrMe2 would be converted to ion-pairs under these conditions. Since this does not reflect actual activation behavior (i.e. complete at ca. 100:1 Al:Zr ratios) we decided to treat all activation steps as irreversible but preserved the rate differences. This resulted in nearly exclusive formation of 2c and its Me3Aladduct 3c (Table , entries 3-4). Evidently, formation of SBIZrMeμ-Me-13,8 (3e) would not occur strictly based on our DFT energetics.