Heating of NiCl2 · 6H2O with 10-fold excess of an oxime having an CH2 group (1–4) at 100 °C for 1 day in air leads to the formation of the dioxime/ato complexes [Ni(dioxime/ato)2] (5–8) formed due to a novel type of metal-mediated nitrosation. Compounds 5–8 were characterized by elemental analyses, FAB (5–7) or APCI (8) mass-spectrometry, IR, 1H and 13C{1H} spectroscopies (for 8), and X-ray structural study has been performed for 5 and 8; the corresponding ketones (9–12) were identified by LC–MS