trans-Bis(N,N-diethylethylenediamine)nickel(II) dibromide

The structure of the title compound, [Ni(C(6)H(16)N(2))(2)]Br(2) or [Ni(Et(2)en)(2)]Br(2) (Et(2)en is asymmetric N,N-diethylethylenediamine), containing an Ni(II) atom (site symmetry 1) in square-planar NiN(4) coordination, is described and contrasted with related structures containing Ni(II) in octahedral coordination with axial X(-) ligands (X(-) = variable anions). The dialkylated N atom has an appreciably longer bond length to the Ni(II) atom [1.9666 (13) angstrom] than does the unsubstituted N atom [1.9202 (14) angstrom]. The Ni-N bond lengths in [Ni(Et(2)en)(2)] Br(2) are significantly shorter than corresponding values in tetragonally distorted [Ni(Et(2)en)(2)X(2)] compounds (X = (-)O(2)CCF(3), OH(2), or (-)NCS), which have a triplet ground state. The electronic configuration in these axially ligated [Ni(Et(2)en)(2)X(2)] compounds populates the metal-based d(x)(2) (2)(-y) orbital, which is Ni-N antibonding in character. Each Et2en ligand in each [Ni(Et(2)en)(2)](2+) cation forms a pair of N-H center dot center dot center dot Br hydrogen bonds to the Br(-) anions, one above and below the NiN(4) square plane. Thus, a ribbon of alternating Br(-) pairs and [Ni(Et(2)en)(2)](2+) cations that are canted at 65 degrees relative to one another is formed by hydrogen bonds.