pubs.acs.org/Organometallics Published on Web 12/28/2010 r 2010 American Chemical Society 334 Organometallics 2011, 30, 334–347 DOI: 10.1021/om101102j Supramolecular Structures from Polycarbene Ligands and Transition Metal Ions Arnab Rit, Tania Pape, Alexander Hepp, and F. Ekkehardt Hahn* Institut f € ur Anorganische und Analytische Chemie, Westf € alische Wilhelms-Universit € at M€ unster, Corrensstrasse 30, D-48149 M€ unster, Germany Received November 24, 2010 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-tetrabromo- benzene 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 H 4 -2a,b(Br) 4 and the trisimidazolium salts of type H 3 -4a,b(Br) 3 have been prepared by alkylation of the remaining free imines of the tetrakis- and trisimidazoles (H 4 -2a 4þ ,H 3 -4a 3þ :R= n-butyl; H 4 -2b 4þ ,H 3 -4b 3þ :R= ethyl). Polyimidazolium salts H 4 -2a,b(PF 6 ) 4 and H 3 -4a,b(PF 6 ) 3 have been synthesized by anion exchange from H 4 -2a,b(Br) 4 and H 3 -4a,b(Br) 3 . Two equivalents of tetraimidazolium salt H 4 -2a(Br) 4 or H 4 -2a,b(PF 6 ) 4 reacts with four equivalents of Ag 2 O to yield via self-assembly molecular cylinders of type [Ag 4 (2a) 2 ]Y 4 (Y - =[AgBr 2 ] - and/or Br - ) or [Ag 4 (2a,b) 2 ](PF 6 ) 4 , respectively. Similarly, reaction of two equivalents of trisimidazolium salts H 3 -4a(Br) 3 or H 3 -4a,b)(PF 6 ) 3 with three equivalents of Ag 2 O yields the molecular cylinder [Ag 3 (4a) 2 ](Y) 3 (Y - =[AgBr 2 ] - and/or Br - ) or [Ag 3 (4a,b) 2 ](PF 6 ) 3 , respectively. Transmetalation of [Ag 4 (2a,b) 2 ](PF 6 ) 4 with four equivalents of [AuCl(SMe 2 )] leads to the formation of the tetranuclear gold(I) complex [Au 4 (2a,b) 2 ](PF 6 ) 4 with retention of the metallo- supramolecular assembly. Analogously, transmetalation of [Ag 3 (4a,b) 2 ](PF 6 ) 3 with three equivalents of [AuCl(SMe 2 )] or CuBr yields the trinuclear gold(I) complexes [Au 3 (4a,b) 2 ](PF 6 ) 3 or the copper(I) complexes [Cu 3 (4a,b) 2 ](PF 6 ) 3 , respectively. Contrary to the metallosupramolecular assemblies of type [M 4 (2a) 2 ] 4þ (M = Ag þ , Au þ ), tetrakisimidazolium salt H 4 -2a(Br) 4 reacts with K 2 PtCl 4 in the presence of NaOAc to yield the square-planar dinuclear complex [Pt 2 (2a)Br 4 ]. 1. Introduction Metal-controlled self-assembly of supramolecular structures has attracted tremendous attention in the last two decades after the first report on dinuclear double-helical complexes by Lehn et al. from bipyridine and copper(I). 1 Subsequently, a large number of self-assembled metallohelicates 2 and other three-dimensional supramolecular structures 3 have been obtained by variation of the metal components and the ligands. Some of these supramolecular assemblies can act as molecular hosts by encapsulating small molecular guests, which might undergo selective chemical transformations within the host molcule. 4 A dramatic rate enhancement has been observed for selective transformations within metallo- supramolecular hosts. 5 Most of the three-dimensional metallosupramolecular structures are built from metal centers at the corners (often palladium or platinum species with cis-coordinated diamines or diphosphines as supporting ligands) that are linked by classical Werner-type polydentate ligands featuring nitrogen and/or oxygen donor atoms, such as pyrazine, 4,4 0 -bipyridine, or 2,4,6-tris(4-pyridyl)-1,3,5-triazine. 3,4 Polydentate ligands with carbon donors have rarely been used for the construc- tion of metallosupramolecular assemblies, although some derivatives with bridging diisocyanide, 6 acyclic diamino- carbenes, 7 and remote N-heterocyclic carbene ligands 8 have been described. 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