Synthesis of mono-, di- and tetra-alkyne functionalized calix[4]arenes: Reactions of these multipodal ligands with dicobalt octacarbonyl to give complexes which contain up to eight cobalt atoms

Abstract

The functionalized mono-alkyne cone-monopropargyl p-tert-butylcalix[4]arene was synthesized by the reaction of p-tert-butylcalix[4]arene with K(2)CO(3) and 3-bromo-1-propyne. More prolonged reaction times led to the formation of the 1,3 cone bis(propargyl)calix[4]arene . The tetra-alkyne species cone-tetrapropargyl p-tert-butylcalix[4]arene and its conformational isomer, 1,3-alternate-tetrapropargylcalix[4]arene may both be prepared via related reaction sequences. The structures of the molecules and were both re-determined by single crystal X-ray diffraction studies. All four functionalized calixarenes react rapidly with dicobalt octacarbonyl to give [(calix[4]arene).{Co(2)(CO)(6)}(n)] species (n = 1, 2 or 4) in which the alkyne functionalities of the propargylcalix[4]arenes are ligated to one or more [Co(2)(CO)(6)] groups. Two products could be harvested from the reaction of [Co(2)(CO)(8)] with the bis-propargyl-calixarene , depending on the reaction conditions and relative molar quantities of the reactants: complex , [1,3-cone bis(propargyl)calix[4]arene.{Co(2)(CO)(6)}(2)], in which each alkyne group is bonded to a [Co(2)(CO)(6)] group, and complex , [1,3-cone bis(propargyl)calix[4]arene.{Co(2)(CO)(6)}], which contains a unligated alkyne and an alkyne group bonded to a Co(2)(CO)(6) unit. The structures of the tetracobalt and octacobalt complexes and were established by single crystal X-ray diffraction studies.