Macrocycles Containing Tin. Ditopic, Tricyclic, Lewis Acidic Hosts with Four Binding Sites.

摘要

A new class of Lewis acidic hosts is described. The hosts are macrotricyclic species containing four tin atoms that serve as the bridgeheads of the macrotricycle and contain an electron withdrawing group to impart Lewis acidic character. Variable length polymethylene chains link the tin atoms. The preparation of two macrotricyclic host precursors and one macrotricyclic host, 1,7,13,19-tetrachloro-1,7,13,19-tetrastann-(17,5,5,.5) tetratriacontane (7), are described. Tin II9 NMR studies of host 7 binding chloride ion in CDC3 at 20 C are reported. Fast exchange between bulk and bound chloride was observed. Host 7 binds one chloride ion strongly and shows no evidence for binding additional chloride ions. These results suggest that chloride is bound within the central cavity of the host with the multiple Lewis acidic sites acting in a cooperative manner. (aw)