Metallocavitands Using Modified Cyclodextrins

CyDs were used as scaffolds for making metallocavitands [7]. Two phosphine units can be highly preorganized on the CyD rim and a metal center can be rigidly held above the entrance of the opened CyD cavity [189-193]. These metallocavitands are expected to lead to the development of new metal catalysts with enhanced selectiv-ities and activities (CyD catalysis is presented in Chapter 4), in particular because of the protection against undesired side reactions provided by substrate inclusion into the CyD cavity and by stabilization of unusual coordination modes. 

The reaction of ligand 107, which has two C(5)-linked CH2PPh2 units at the A and D positions of a-CyD, with one equivalent of AgBp4 in MeCN led to quantitative formation of the complex [Ag(107)(CH3CN)2]BF4 (108), which is only stable in the presence of a large excess of MeCN ( 15 equiv.) [190]. The coordination of MeCN molecules is stabilized by the CyD cavity. The addition of benzonitrile (ca. 8 equiv.) to a solution of 108 in a CHCls/MeCN mixture (108/MeCN = 1 15) resulted in the quantitative formation of complex 109, in which a single benzonitrile molecule, accommodated in the CyD cavity, is coordinated to the silver ion. 

1 Easton CJ, Lincoln SF, Motived Cydodextrins Scaffolds and Templates for Supramolecular Chemistry, Imperial College Press, London, 1999 pp 43-100. 

Fenivesi E, Ueno a, in Comprehensive Supramolecular Chemistry, Vol. 3, Lehn JM, Atwood JL, Davies JE, MacNicol DD, VOGTLE E, Eds, SZEJTLI J. OsA T, Vol. Eds., Pergamom Oxford, 1996  

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