Exploiting Multimetallic Cooperativity in the Ring-Opening Polymerization of Cyclic Esters and Ethers.

Trimetallic aluminum catalysts featuring three Al centers in a near linear arrangement were reported for ε-CL ROP ( 85 – 89 , Figure 15 ) and showed a trend of increased catalytic activity with the increased steric bulk of aliphatic substituents, from i Pr ( 87 ) < t Bu ( 85 ) < adamantyl ( 86 ) (25 °C, toluene, [ε-CL]:[Cat]:[BnOH] 100:0.5:2.5). 65 The trimetallic t Bu- and phenyl-substituted complexes both outperformed their bimetallic counterparts ( 85 and 89 vs 68 and 64 ), with the k obs value of 85 being 15 times greater than that of 68 , and 89 being twice that of 64 .

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