Hexa-coordinated aluminum and gallium cations derived from indazole

Abstract

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 [AlCl 3] 2 and [GaCl 3] 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/CH 2Cl 2 afforded in good yield complex 2 {[AlCl 2(IndH) 4] +[AlCl 4] −·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 [ECl 2(IndH) 4] + [ECl 4] − (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 [ECl 2(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 [ECl 4] − 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 AlCl 4 - anion interacts with two [MCl 2(Ind-H) 4] + cations and two THF molecules through Cl⋯H intermolecular interactions (2.855–2.922 Å) and one [MCl 2(Ind-H) 4] + cation interacts with two cations through ClL 4MCl⋯H interactions (2.922 Å). Whereas in 1 and 3, six AlCl 4 - anions interact through Cl⋯H intermolecular interactions (2.795–2.925 Å) with one [MCl 2(Ind-H) 4] + cation and this latter interacts with other three [MCl 2(Ind-H) 4] + cations through C⋯H interactions (2.769–2.888 Å). Additionally, every chlorine atom in the [MCl 2(Ind-H) 4] + cationic moieties is bounded by NCH⋯ClM or NH⋯ClM intramolecular-tetrafurcated hydrogen bonds (2.434–2.907 Å).