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Supramolecular structures from polycarbene ligands and transition metal ions
, Pape T., Hepp A., Hahn F.E.
Published in ACS Publications
Volume: 30
Issue: 2
Pages: 334 - 347
The synthesis of cylinder-type carbene complexes from polycarbene ligands and coinage metal ions via metal-controlled self-assembly has been explored. Imidazole reacts with 1,2,4,5-tetrabromobenzene or 1,3,5-tribromobenzene to give 1,2,4,5-tetrakis(1-imidazolyl)benzene (1) and 1,3,5-tris(1-imidazolyl)benzene (3), respectively. The tetrakisimidazolium salts of type H4-2a,b(Br) 4 and the trisimidazolium salts of type H3-4a,b(Br) 3 have been prepared by alkylation of the remaining free imines of the tetrakis- and trisimidazoles (H4-2a4+, H 3-4a3+: R = n-butyl; H4-2b4+, H 3-4b3+: R = ethyl). Polyimidazolium salts H 4-2a,b(PF6)4 and H3-4a,b(PF 6)3 have been synthesized by anion exchange from H 4-2a,b(Br)4 and H3-4a,b(Br)3. Two equivalents of tetraimidazolium salt H4-2a(Br)4 or H 4-2a,b(PF6)4 reacts with four equivalents of Ag2O to yield via self-assembly molecular cylinders of type [Ag 4(2a)2]Y4 (Y- = [AgBr 2]- and/or Br-) or [Ag4(2a,b) 2](PF6)4, respectively. Similarly, reaction of two equivalents of trisimidazolium salts H3-4a(Br)3 or H3-4a,b)(PF6)3 with three equivalents of Ag2O yields the molecular cylinder [Ag3(4a) 2](Y)3 (Y- = [AgBr2]- and/or Br-) or [Ag3(4a,b)2](PF 6)3, respectively. Transmetalation of [Ag 4(2a,b)2](PF6)4 with four equivalents of [AuCl(SMe2)] leads to the formation of the tetranuclear gold(I) complex [Au4(2a,b)2](PF 6)4 with retention of the metallosupramolecular assembly. Analogously, transmetalation of [Ag3(4a,b)2](PF 6)3 with three equivalents of [AuCl(SMe2)] or CuBr yields the trinuclear gold(I) complexes [Au3(4a,b) 2](PF6)3 or the copper(I) complexes [Cu 3(4a,b)2](PF6)3, respectively. Contrary to the metallosupramolecular assemblies of type [M4(2a) 2]4+ (M = Ag+, Au+), tetrakisimidazolium salt H4-2a(Br)4 reacts with K 2PtCl4 in the presence of NaOAc to yield the square-planar dinuclear complex [Pt2(2a)Br4]. © 2010 American Chemical Society.
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PublisherACS Publications
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