THE CRYSTAL-STRUCTURE OF NE)-(2,4-PENTANEDIONATO)-(O,O'-NITRATO)NICKEL(II)]

The title compound, [Ni(acac)(Phi en Phi)(O2NO)] C19H23N3NiO5, is mono clinic, space group P2(1)/a, Z = 4 Cell dimensions are a = 13.659(7) A ngstrom, b = 12.746(6) Angstrom, c = 13.707(7) Angstrom and beta = 117 .71(3)degrees. A total of 3498 reflections were measured with a PC-com puter controlled PHILIPS PW 1100 automatic diffractometer using MoK(a) lpha radiation. The structure was refined by full-matrix least squares to a conventional R = 0.038 for 2623 observed reflections with I > 2 sigma(I). The coordination around the central nickel atom is a distort ed octahedron with the apices of the octahedron occupied by the oxygen atoms of the acetylacetonato (2,4-pentanedionato) moiety, the nitroge n atoms of the N,N'-diphenyl-1,2-diaminoethane (Phi en Phi) ligand, an d two of the oxygens on the nitrate group, [NO3](-). As a result of th is coordination a resonance-stabilised six-membered beta-dionato chela te ring, a five-membered chelate ring with the 1,2-diamine ligand in t he gauche conformation, and a four-membered cheIate ring are formed, w ith the NO3- acting as an O,O' chelating ligand. As expected, the bite angle becomes more acute as the ring size diminishes, the actual valu es being 95.43 degrees, 81.83 degrees, and 59.63 degrees respectively.