Crystal structure of a dimeric nickel(II) complex with 3-imidazoline nitroxide radical

Abstract

The crystal structure of an unusual dimeric Ni(II) complex with 3-imidazoline nitroxide LH=C9H14N2O2 of the formula Ni2(LH)4 has been determined. The structure is molecular, space group P21/c, with a=12.150(3) A, b=11.229(3) A, c=15.780(4) A, β=101.59(3)o, and d calc =1.54 g/cm3, for Z=2; V=2109(1) A3, R=0.059. In the centrosymmetric dimer, the Ni...Ni distance is 3.254(2) A; the coordination polyhedron of Ni is a square pyramid (the coordination number is 5) formed by the donor O and N atoms of LH ligands acting as the bidentate-cyclic and bidentate bridged-cyclic structures. The Ni−O and Ni−N distances are 1.989(7) and 2.032(8) A, respectively (for the atoms forming the pyramid base), and 2.000(8) A to the apical N atom. The Ni atom is displaced from the base to the apex of the pyramid by 0.35 A. The interatomic distances and the bond angles in the ligands agree with those for the previously studied M(LR)2 complexes. The distances between the Ni(II) ions and the $$\begin{array}{*{20}c} \backslash \\ / \\ \end{array} N$$ ∸ O O atoms inside the Ni(LH)2 fragments are 5.39(1) and 5.45(1) A, the intermolecular Ni...O∸ distances exceed 6 A, and the ∸O...O∸ distances are as long as 4.73(1) A.