A complex reaction route was developed for the preparation of flower-like cobalt nanocrystals by using 2-hydroxy-4-(1-methylheptyl) benzophenone oxime (N530), a normally effective chelate extracting agent. X-ray powder diffraction pattern shows that the cobalt nanocrystals coexist of both hexagonal close-packed (hcp) and cubic close-packed (ccp) forms, with flower-like architecture characterized by a field emission scanning electronic microscopy. The magnetic coercivity Hc of the as-prepared cobalt crystals came up to 360 Oe at room temperature. The existence of the precursor N530-CoCl2 Complex was determined by a Fourier transform infrared (FT-IR) spectrometer. Experiments suggested that the existence and the framework structure of the precursor complex have a considerable effect on the final architectures of cobalt nanocrystals. (c) 2004 Elsevier B.V. All rights reserved.