Spectral characterisation of five volatile bis(N-R-salicylaldimine)nickel(II) (where n-R = methyl to pentyl) complexes and single crystal study on methyl analogue

Five novel volatile complexes of nickel, namely bis(N-R-salicylaldimine)nickel(II) (where n-R = methyl to pentyl), were characterised using fast atom bombardment mass spectrometry (FABMS). The molecular masses (M) of the monomeric species [NiL2] (L = N-R-salicylaldimine) were identified to be m/z (Dalton) = 327, 355, 383, 411 and 439, respectively, for methyl to pentyl homologues in agreement with the theoretical values. The melting and sublimation/vapourisation temperatures under reduced pressure (∼2 mbar) were indicative of a negative volume change upon melting for all the homologues besides confirming their volatility to nil residue in the temperature range 305–340 °C. The coordination of nitrogen (N with n-alkyl chains) to the nickel centre that is thought to be responsible for their volatility was confirmed by Fourier-transformed infrared (FT-IR) spectroscopic analysis; ν(Nisingle bondN) (cm−1): 502 (methyl), 522 (ethyl), 533 (propyl), 531 (butyl) and 549 (pentyl). Single crystal XRD analysis of the first member of this series, namely bis(N-methyl-salicylaldimine)nickel(II), confirmed the existence of this complex to be a monomer in the solid state and the crystal data are: 293 (2) K, a = 8.352 (3) Å, b = 7.103 (2) Å, c = 12.1369 (18) Å, α = 90°, β = 92.850 (18)°, γ = 90°, monoclinic, space group P21/a, Z = 2.