Calixarenes: Structure of an acetonitrile inclusion complex and some transition metal rimmed derivatives

The host t-butylcalix[4]arene, 1a, forms a 1:1 inclusion compound with acetonitrile as guest. The inclusion compound has been isolated and characterised by X-ray analysis of a twinned crystal at 123 K. The acetonitrile guest lies on a crystallographic four-fold symmetry axis passing through the centre of the bowl of 1a which adopts a regular cone conformation. A known tetradentate and a new tridentate phosphinitocalix[4]arene derivative, 2a and 2c respectively, have been synthesized from 1a and Ph₂Cl. Both 2a and 2c show a strong ability to coordinate with late transition metals and new complexes of gold(I), palladium(II) and platinum(II) are reported.