Preparation and properties of inclusion compounds of cobalt cluster complexes with γ-cyclodextrin

Abstract

Inclusion compounds of di-, tri-, and tetranuclear transition metal complexes with γ-cyclodextrin (CD) have been prepared as the first example of an inclusion compound of cyclodextrin with a metal cluster complex. High yields of crystalline one-to-one inclusion compounds were obtained by the treatment of η 2-acetylenedicobalt hexacarbonyl complexes with γ-CD. μ 3-Phenylmethylidynetricobalt nonacarbonyl, and η 6-mesitylenetetracobalt nonacarbonyl also form inclusion compounds with γ-CD. The formation of inclusion compounds is selective. γ-CD forms 1 : 1 host : guest inclusion compounds with η 2-phenylacetylene- and η 2-phenylmethylacetylenedicobalt hexacarbonyls, but not with the sterically larger η 2-diphenyldicobalt hexacarbonyl. Neither α-CD nor β-CD formed inclusion compounds with any of the cobalt cluster complexes tested. The metal cluster complexes included in γ-CD are thermally more stable than the free complexes.