Halido‐Bridged Dinuclear Nickel and Zinc Complexes with a Bis(tripodal) Octaamine Ligand – Unusual Coordination Mode of an ortho‐Phenylenediamine

Abstract

AbstractA potentially dinucleating octaamine ligand H6‐4 consisting of two aliphatic tripodal tetraamine units connected by an ortho‐phenylenediamine spacer has been synthesized. Treatment of H6‐4 with Ni(BF4)2·6H2O or H10‐4(BF4)4 with Et2Zn in the presence of a halide source leads to the formation of the dinuclear complexes [Ni2(μ‐Cl)2(H6‐4)](BF4)2 (5) and [Zn(μ‐F)(H6‐4)](BF4)3 (6), respectively, which were structurally characterized by X‐ray diffraction studies. In both 5 and 6 the ligand coordinates with four nitrogen donors to each metal center. The ortho‐phenylenediamine bridging unit coordinates in an unprecedented fashion with each of its amine functions to only one of the metal centers. The dinickel complex 5 possesses two bridging chlorido ligands that differ notably in their Cl–Ni bond lengths, due to interactions of four amine N–H protons with one of the chlorido bridges leading to a reduced donor ability. The dizinc complex 6 was synthesized without addition of an external halide source. The two zinc atoms in 6 facilitate the abstraction of a fluoride from a tetrafluoroborate anion through a cooperative activation by the two adjacent metal centers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)