The metal-controlled self-assembly of organometallic molecular cylinders from a series of imidazo[1,5-a]pyridine-based tris-NHC ligands is described in this report. The imidazo[1,5-a]pyridinium salts H3 -L(PF6 )3 (L=4 a-4 c) were treated with 1.5 equivalents of Ag2 O to yield the trinuclear AgI hexacarbene cages [Ag3 (L)2 ](PF6 )3 (L=4 a-4 c), in which three AgI are sandwiched between the two tricarbene ligands. The silver(I) complexes [Ag3 (L)2 ](PF6 )3 underwent a facile transmetalation reaction in the presence of 3 equivalents of [AuCl(tht)] (tht=tetrahydrothiophene) to furnish the trinuclear AuI cylinder-like cages [Au3 (L)2 ](PF6 )3 (L=4 a-4 c) without destruction of the metallosupramolecular structure. The new hexacarbene assemblies feature a large cavity that can easily accommodate a molecule of dimethyl sulfoxide as molecular guest. This is the first study of a unique "host-guest" system containing an organometallic cylinder-like cage derived exclusively from poly-NHC ligands.
Keywords: carbenes; host-guest systems; nitrogen heterocycles; organometallic chemistry; self-assembly; transmetalation.
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