Co-ordination chemistry of arenediazoate anions: synthesis and X-ray crystallographic characterisation of η-cyclopentadienyl-(anti-p-nitrobenzenediazoato-N1)(triphenylphosphine)nickel(II), [Ni(η-C5H5)(PPh3)(ON2C6H4NO2-p)]

Abstract

Sodium anti-p-nitrobenzenediazoate reacts with [Ni(η-C₅H₅)(PPh₃)Cl] to give an 83% yield of the title complex [Ni(η-C₅H₅)(PPh₃)(ON₂C₆H₄NO₂-p](3), the first authenticated example of an arenediazoato-complex. Crystals of complex (3) are triclinic, space group P, with two molecules in a unit cell of dimensions a= 7.822(1), b= 9.618(1), c= 19.011(2)Å, α= 79.57(1), β= 80.96(1), γ= 109.04(1)°, and Z= 2. The structure was solved by the heavy-atom method and refined by full-matrix least-squares calculations. All hydrogen atoms were located from difference syntheses. Final R= 0.043 for 2 763 reflections with I > 2σ(I). The arenediazoato-ligand has an anti configuration and co-ordinates to nickel via N(1) in a monohapto-fashion. The atoms of the NiONNC₆H₄ moiety are close to being coplanar. Principal dimensions include Ni–N(1) 1.901(4), Ni–P 2.166(1), Ni–C(cyclopentadienyl) 2.103(6)–2.187(7), and Ni ⋯ O(1) 2.784(4)Å. The structural data are interpreted in terms of significant contributions from both diazoate and N-nitrosoamine anion resonance structures to the ground state of the co-ordinated arenediazoato-ligand.