Metallocycle and ring-opening polymerization of silver(I) complexes with 1,3-bis(4,5-dihydro-1 H-imidazol-2-yl)benzene ligand

Abstract

The reaction of 1,3-bis(4,5-dihydro-1 H-imidazol-2-yl)benzene (bib) ligand with silver(I) nitrate in a 1:1 molar ratio generated a [2 + 2] metallocyclic complex [Ag 2(bib) 2](NO 3) 2 · 2H 2O, in which bib ligand displayed in cis configuration. When the additional competing ligands/counterions, such as oxlate salt, 1,2-diaminoethene (en), 1,3-diaminopropane (pn), NO 2 - and VO 3 - were introduced, respectively, to the above-mentioned reaction solution, ring-open polymerization of sliver(I) complexes {[Ag(bib)]NO 3 · H 2O} n ( 1), {[Ag(bib) 2]X} n ( X = NO 3 - ( 2), ClO 4 - ( 3)), {[Ag 2(bib) 2(NO 2)](NO 2) · 19/8H 2O} n ( 4) and {[Ag 2(bib) 2](V 4O 12) 0.5 · 3H 2O · 2MeCN} n ( 5) were generated. In compounds 1, 4 and 5, bib ligand adopts trans configuration and twists around the Ag–Ag axis, giving rise to single-stranded helical structure with short adjacent Ag⋯Ag distances of 3.56, 3.56, 3.50 and 3.63 Å, respectively. Compounds 2 and 3 are 1D coordination polymers fusing the [2 + 2] metallocycle [Ag 2(bib) 2] 2+, in which bib ligand exhibits in cis configuration and the metallocycles have longer Ag⋯Ag distances of 8.52 Å in 2 and 8.61 Å in 3 along with the strong intracyclicπ–π interactions between phenyl groups. Cis and trans configurations of bib coexist in solution and crystallize in complexes 1 and 2 in the solid state in the presence of en or pn. The solution of 1 and 2 can be converted into 3 via the addition of the bulky ClO 4 - counter anion or into 4 through introduction of the competing ligand/conuterion NO 2 - .