Synthesis, reactivity and crystal structure of [1,4-bis(4-tolyl)tetraazadiene] (h5-cyclopentadienyl)nickel

Abstract

The complex [ 1,4-bis(4-tolyl)tetraazabutadiene] (v5-cyclopentadieny1)nickel has been prepared by reaction of his($- cyclopentadieny1)nickel with 4-tolyl azide. The crystal and molecular structures have been determined by a single-crystal X-ray diffraction study. Crystals are monoclinic, space group P2,/c, with Z = 4 in a unit cell of dimensions a = 10.277 (4) A, b = 15.139 (6) A, c = 11.455 (3) A, and p = 102.31 (3)'. The final R value is 0.032 for 3150 reflections. The structure comprises mononuclear units with each central nickei atom coordinated to an $-bonded cyclopentadienyl group and, via two nitrogen atoms at the 1- and 4-positions, to the tetraazabutadiene system. The resultant NiN4 ring is planar with the aryl substituents twisted 45' out of this plane. The tetraazabutadiene moiety has a short central N(2)-N(3) distance (1.278 (2) A) and two longer adjacent N-N bonds (1.345 (2) A average). This complex can be reacted further either with aryl azides to produce bis(tetraazabutadiene)nickel complexes or with tert-butyl isocyanide to yield bis(rert-butyl isocyanide) [ 1,4bis(4-tolyl)tetraazabutadiene]nickel. The title complex is paramagnetic. The ESR spectrum shows hyperfine coupling of the unpaired electron with two nitrogen atoms (gl = 1.97, g2 = 2.01, g3 = 2.08, AN(g2)= 12 G). XPS spectra of the Ni(2p) and N(1s) bands exhibit a shake-up satellite in the latter. The bonding in this compound is discussed on the basis of the crystal structure and the spectral data.