Photoreaction of adsorbed diiodomethane: halide effects of a series of neutral palladium(II) coordination cages

A series of Pd6L4-type neutral coordination cages, (Pd6X12L4I (X- = Cl- and Br-), are constructed via self-assembly of (COD)PdCl2 and K2PdBr4 with C-3-symmetric N,N',N"-tris(2-pyridinyErnethyl)-1,3,5-benzenetricarboxamide (L), respectively. The iodide analogue (Pd6I12L4] is smoothly synthesized from [Pd6Br12L4] in the presence of CH2I2 under mild conditions. The replacement of bromide to iodide in the nanocage system represents a landmark achievement in synthetic-methodology development. The CH2I2 molecules are adsorbed in the order [Pd6I12L4] > [Pd6Br12L4] > [Pd6Cl12L4] and in the "like-attracts-like" pattern, presumably owing to the van der Mats force. Irradiation of (Pd6I12L4]center dot 3.5CH(2)I(2) with 1-methylcyclohexene in chloroform at 350 nm preferentially affords the cyclopropanation product.