Proton Controlled Supramolecular Assembly: A Comparative Structural Study of Bis(2-guanidinobenzimidazolo)nickel(II) with Bis(2-guanidinobenzimidazole)nickel(II) Nitrate and 2-guanidinobenzimidazole

Abstract

Previously studies have shown that when 2-guanidinobenzimidazole complexes with a number of transition metal ions it tautomerises so that, in contrast to the free ligand structure, no intermolecular hydrogen bonding between bound ligands occurs. In the present study it is demonstrated that ligand deprotonation to yield bis(2-guanidinobenzimidazolo)nickel(II) restores much of the original hydrogen bonding capability of the uncomplexed ligand. The structure of this neutral complex is compared to the previously reported structure of its diprotonated derivative, bis(2-guanidinobenzimidazole)nickel(II) nitrate, as well as to the structure of the uncomplexed ligand. In contrast to the dicationic species, the neutral complex exists in two enantiomeric forms that assemble to form an extended supramolecular lattice, containing channels through its structure. The walls of the channels are made up of ‘strings’ of complex molecules and are held in position by hydrogen bonding between the bound ligands and dimethyl sulfoxide (solvent) molecules as well as water molecules. Some of the solvent molecules lie within the channels and some outside. The hydrogen bonding motif responsible for chain formation differs from that found in the free ligand structure.     

Neue Komplexe des Titans mit Bis(trimethylsilyl)amido-Liganden

New Complexes of Titanium with Bis(trimethylsilyl)amido Ligands The reaction of cp′TiCl₃ with LiN(SiMe₃)₂ · Et₂O 1 yield the compounds cp′TiCl₂N(SiMe₃)₂ (cp′ = C₅H₅ 2 , C₅H₄SiMe₃ 3 , C₅H₃(SiMe₃)₂ 4 , C₅Me₅ 5 ) and cp′TiCl[N(SiMe₃)₂]₂ (cp′ = C₅H₅ 6 ). Compound 2 was characterized by an X-ray structural analysis with space group P2₁/n and unit cell dimensions of a = 1 660.9(7), b = 688.6(3), c = 1 739.1(8) pm and β = 117.18(3)°.