A calix[4]arene carceplex with four Rh24+ fasteners

It is shown that a spheroidal carceplex can be assembled by linking two bowl-shaped calix[4]-arenes via four dimetal units, (DAniF)(2)Rh-2 (DAniF = N,N'-di-p-anisylformamidinate), with a molecule (diethyl ether) or a cation (tetraethylammonium ion) trapped inside. The tetraethylammonium carceplex, 1b, has been characterized by X-ray crystallography, H-1 NMR, IR, and mass spectrometry. The tetraethylammonium ion fits snugly in the interior of the spheroidal carceplex. A two-fold axis of the tetrahedral cation coincides with the idealized four-fold axis of the cage, and the cation is disordered over two rotational orientations. Only one axial position on each dirhodium unit is occupied by a ligand, CH3CN or H2O. The carceplex is very stable, and the axial ligands can be exchanged in single crystals without disrupting the crystallinity of the samples. In this way, a red crystal of the complex with all axial positions occupied by acetonitrile can be transformed to a green crystal of the complex with two axial positions having acetonitrile and the other two having water by simply putting the crystal in contact with distilled water. The calix[4]arene used to make the carciplex structure is 25,26,27,28-tetra-n-propoxycalix[4]arene-5,11,17,23-tetracarboxylic acid. By employing 25,26,27,28-tetrapropoxy-5,17-dibromo-calix[4]arene-11,23-dicarboxylic acid, two 1:1 dimetal: calixarene compounds have also been made and characterized: 2, cis- Rh-2(DAniF)(2)(calix)(CH3OH), and 3, Cis-Mo-2(DAniF)(2)(calix). The Rh-Rh distances in 1b are in the range of 2.410(2)-2.428(2) Angstrom, that in 2 is 2.4383(4) Angstrom, and the Mo-Mo distance in 3 is 2.0931(4) Angstrom.