Methyl or ethyl makes the difference: Synthesis and solid-state structure of 9,10-dialkyl-9,10-dihydro-9,10-digallaanthracenes

摘要

The donor-free 9, 10-dialkyl-9, 10-dihydro-9, 10-digallaanthracenes 1 (alkyl: methyl) and 2 (alkyl: ethyl) were prepared by reaction of 1,2-di(chloromercurio)benzene with the corresponding trialkylgallium. and isolated as colourless air- and moisture sensitive crystalline compounds. In the solid-state structure of 1, two slightly different monomers 1A and 1B are found, which form a dimer 1A and 1B held together by "medium" strong gallium arene pi-interactions. Further weak pi-interactions between 1A and 1A and 1B and 1B constitute a one-dimensional coordination polymer containing strands of the composition [center dot center dot center dot(1A center dot center dot center dot 1B)center dot center dot center dot(1B center dot center dot center dot 1A)center dot center dot center dot](n). In contrast, compound 2 crystallizes in the form of distinct molecular units without any further intermolecular pi-interactions. The molecular units possess D-2d symmetry and are built by strong n-interactions between two digallaanthracene monomers. Two symmetrical aryl group bridges between two gallium atoms are observed for the first time in the subunits of 2. By addition of a Lewisbase (THF, Pyridine) to 2, a monomeric planar digallaanthracene framework is restored, as proven by an X-ray crystal structure analysis of 2 center dot 2Py. The different structures of 1 and 2 are explained on the basis of steric effects. (c) 2005 Elsevier B.V. All rights reserved.