| Abstract
| - The metallomonomer (vinyl dppe)Pt[(R)-Bu2BINOL] (1) was copolymerized with ethylene glycoldimethacrylate to produce the molecularly imprinted polymer (MIP) P1. The chiral imprinting ligand (R)-Bu2BINOL was removed from P1 by treatment with HCl or an excess of α,α,α-trifluoro-m-cresol, BINOL, orBr2BINOL, giving polymers P2−P5. The amount of imprinting ligand released from P1 varied inversely withthe steric bulk of the cleaving agent, indicating that a distribution of Pt sites with different accessibilitiesexists in the MIP. Exposure of P3 (containing Pt(OAr)2 centers surrounded by (R)-Bu2BINOL-shaped cavities)to rac-BINOL, an imprinting ligand analogue, led to preferential rebinding of the imprinted enantiomer vialigand exchange. Both aggregate selectivity and extent of reaction (percent of the total Pt sites in the MIP thatparticipated in rebinding) increased with rebinding time and with temperature, up to 69% ee and 58% Pt sitesrebound, respectively. A positive linear correlation between selectivity and reactivity was observed. Open,easily accessible Pt sites were proposed to be less selective than unreactive sites because their associatedchiral cavities are less well-defined and therefore less capable of shape-based enantiodiscrimination. The kineticselectivity of the least reactive sites in P3 was assessed by sequential rebinding of rac-BINOL and then rac-Br2BINOL. Rebound BINOL was recovered from 8 to 20% of the least reactive Pt sites accessible in the MIPin 89−94% ee. All data indicate that chiral cavities (outer sphere) associated with the reactive Pt centers inthese MIPs are responsible for the selectivities observed for stoichiometric ligand-exchange reactions at themetal center.
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