Structures of hexachloroniobate(V) salts of the 1-methylimidazole/1-methylimidazolium and 2-methylimidazolium cations

The 1-methylimidazole/1-methylimidazolium title compd. (I) is triclinic, space group P?1, with a 7.111(2), b 8.042(1), c 8.045(2) Å, ? 78.65(2), ? 87.02(2), and ? 70.04(2)°; dc = 1.844 for Z = 1; R = 0.056, Rw = 0.057 for 978 reflections.. The 2-methylimidazolium title compd. (II) is monoclinic, space group C2/c, with a 21.43(1), b 6.851(2), c 17.65(1) Å, ? 99.41(2)°; dc = 2.02 for Z = 8, R = 0.030, Rw = 0.038 for 1695 reflections. At. coordinates are given. Both salts contain approx. octahedral [NbCl6]- anions with Nb-Cl bond lengths of 2.326(2)-2.378(2) Å. I contains the proton-bridged 1-methylimidazole/1-methylimidazolium cation, whereas the fully N-protonated 2-methylimidazolium ion is present in II. Cohesion in the crystals is achieved by dipolar interactions between Cl atoms of [NbCl6]- and imidazole C-H groups for I and II, as well as N-H...Cl H bonds for II. [on SciFinder(R)]