Hexa-coordinated aluminum and gallium cations derived from indazole

trans-Dichloro-tetrakis-(indazole)aluminum(III) tetrachloroaluminate(III) 1 and trans-dichloro-tetrakis-(indazole)gallium(III) tetrachlorogallate(III) 3 were obtained by the asymmetric cleavage of the chloride-bridged dimers [AlCl3]2 and [GaCl3]2 with two moles of indazole and characterized by NMR, X-ray diffraction, EA and IR. The synthesis of 3[1] was improved (yield 86%) using methylene chloride at room temperature. The addition of THF to a solution of 1/CH2Cl2 afforded in good yield complex 2 {[AlCl2(IndH)4]+[AlCl4]−·4THF}. The crystal structures of these complexes are monoclinic in the space groups P2(1)/n (1), C2/c (2) and P2(1)/n (3). The unit cells of 1–3 contain ion pairs [ECl2(IndH)4]+ [ECl4]− (E = Al and Ga) with multiple hydrogen interactions (Cl⋯H 2.434–2.925 Å, O⋯H 1.984–2.665 Å, C⋯H 2.769–2.888 Å). The [ECl2(IndH)4]+ cations show hexa-coordinated octahedral aluminum and gallium atoms with two chlorine atoms in anti positions and four coplanar nitrogen atoms from the indazole ligands. The [ECl4]− anions have a tetrahedral coordination geometry around the central atom. In the lattice, the presence of THF molecules simplifies the weak interactions network in 2, so one AlCl4- anion interacts with two [MCl2(Ind-H)4]+ cations and two THF molecules through Cl⋯H intermolecular interactions (2.855–2.922 Å) and one [MCl2(Ind-H)4]+ cation interacts with two cations through ClL4MCl⋯H interactions (2.922 Å). Whereas in 1 and 3, six AlCl4- anions interact through Cl⋯H intermolecular interactions (2.795–2.925 Å) with one [MCl2(Ind-H)4]+ cation and this latter interacts with other three [MCl2(Ind-H)4]+ cations through C⋯H interactions (2.769–2.888 Å). Additionally, every chlorine atom in the [MCl2(Ind-H)4]+ cationic moieties is bounded by NCH⋯ClM or NH⋯ClM intramolecular-tetrafurcated hydrogen bonds (2.434–2.907 Å).

trans-Dichloro-tetrakis-(indazole)aluminum(III) tetrachloroaluminate(III) 1 and trans-dichloro-tetrakis-(indazole)gallium(III) tetrachlorogallate(III) 3 were afforded by the asymmetric cleavage of chloride-bridged dimeric [AlCl3]2 and [GaCl3]2 compounds with indazole. 2 was prepared by addition of THF to a solution of 1/CH2Cl2 at −20 °C. The unit cells of 1–3 contain discrete [MCl2(Ind-H)4]+ [MCl4]− ions (M = Al, Ga) with multiple Cl⋯H, C⋯H [only for 2: OTHF⋯H] hydrogen bonds with interatomic distances shorter than the corresponding sum of the van der Waals radii, resulting in a stabilizing weak interactions network.Figure optionsDownload as PowerPoint slide