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

The reaction of 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene (bib) ligand with silver(I) nitrate in a 1:1 molar ratio generated a [2 + 2] metallocyclic complex [Ag2(bib)2](NO3)2 · 2H2O, 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)]NO3 · H2O}n (1), {[Ag(bib)2]X}n ( X = NO 3 - (2), ClO 4 - (3)), {[Ag2(bib)2(NO2)](NO2) · 19/8H2O}n (4) and {[Ag2(bib)2](V4O12)0.5 · 3H2O · 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 A, respectively. Compounds 2 and 3 are 1D coordination polymers fusing the [2 + 2] metallocycle [Ag2(bib)2]2+, in which bib ligand exhibits in cis configuration and the metallocycles have longer Ag⋯Ag distances of 8.52 A in 2 and 8.61 A 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 - .