Trimethyl-aluminium and -gallium derivatives of calix[4]arenes: cone (mono-metallic) or doubly flattened partial cone (tetrametallic) conformations

Reaction of calix[4]arene (H4L) or p-But-calix[4]arene (H4L′) with MMe3(M = Al, Ga) in toluene affords fully deprotonated, alkyl-metal rich complexes [(L or L′)(M-Me)2(MMe3)2] with the calixarene adopting a doubly flattened partial cone conformation; reaction of 1,3-dimethyl ether p-But-calix[4]arene (H2L″) with AlMe3 yields [(L″)AlMe], the metal-bound alkyl group exo to the cavity of the calixarene in a cone conformation.