Herein, we present a novel strategy to reversibly transform the spatial environment around a nickel center by combining (S)PoxIms 1a-d (Figure ) as multifunctional ligands and tris(pentafluorophenyl)aluminum as an LA, where the geometry of the Ni center is interconverted between tetrahedral and trigonal planar (Figure , right). We quantitatively evaluated the variation of the spatial environment, i.e., the volume and shape of the space, and the electronic state around the nickel center based on single-crystal X-ray diffraction (SC-XRD) and X-ray absorption spectroscopy (XAS) analyses.