Effect of methyl-ene versus ethyl-ene linkers on structural properties of tert-butyl and mesityl bis-(imidazolium) bromide salts.

The crystal structures of ligand precursor bis-(imidazolium) salts 1,1'-methyl-enebis(3-tert-butyl-imidazolium) dibromide monohydrate, C(15)H(26)N(4) (+)·2Br(-)·H(2)O or [ (tBu)NHC(2)Me][Br](2)·H(2)O, 1,1'-(ethane-1,2-di-yl)bis-(3-tert-butyl-imidazolium) dibromide dihydrate, C(16)H(28)N(4) (+)·2Br(-)·2H(2)O or [ (tBu)NHC(2)Et][Br](2)·2H(2)O, 1,1'-methyl-enebis[3-(2,4,6-tri-methyl-phen-yl)imidazolium] dibromide dihydrate, C(25)H(30)N(4) (2+)·2Br(-)·2H(2)O or [(Mes)NHC(2)Me][Br](2)·2H(2)O, and 1,1'-(ethane-1,2-di-yl)bis-[3-(2,4,6-tri-methyl-phen-yl)imidazolium] dibromide tetra-hydrate, C(26)H(32)N(4) (2+)·2Br(-)·4H(2)O or [(Mes)NHC(2)Et][Br](2)·4H(2)O, are reported. At 293†K, [ (tBu)NHC(2)Me][Br](2)·H(2)O crystallizes in the P2(1)/c space group, while [ (tBu)NHC(2)Et][Br](2)·2H(2)O crystallizes in the P2(1)/n space group at 100†K. At 112†K, [(Mes)NHC(2)Me][Br](2)·2H(2)O crystallizes in the ortho-rhom-bic space group Pccn while [(Mes)NHC(2)Et][Br](2)·4H(2)O crystallizes in the P2(1)/c space group at 100†K. Bond distances and angles within the imidazolium rings are generally comparable among the four structures. All four bis-(imidazolium) salts co-crystallize with one to four mol-ecules of water.