Finally, we further explored the electronic structures of the Ni 3d orbitals in the solid state for 2a and 3a based on Ni L2,3-edge XAS experiments using the partial fluorescence yield (PFY) method. In the cases of 2a and Ni(cod)2, the absorption maxima on the Ni L3-edge appear at 856.0 and 856.2 eV, respectively, with a shoulder peak in their lower-energy regions (Figure ). These Ni L2,3-edge XAS spectra represent spectroscopic features characteristic of tetrahedral nickel complexes with a d 10 electron configuration (formally Ni(0)). In contrast, for 3a, the peak maximum shifts toward the lower-energy region to 852.9 eV, clearly indicating that the 3d orbitals are stabilized through the formation of the 16-electron complex with a vacant 4pz orbital. In fact, the energy levels of the unoccupied frontier MOs of 3a are substantially lower than those of 2a, showing good agreement with the experimental Ni L2,3-edge XAS data (Table ). Furthermore, a broad signal is observed in the higher energy region at 854-858 eV. Based on the results of the In summary, we have reported a strategy that reversibly modulate the electronic state and spatial environment around metal centers that bear multifunctional ligands based on the use of Lewis acids. To this end, a series of N-phosphine oxide-substituted N-heterocyclic carbenes, referred to as (S)PoxIms, was employed, as (S)PoxIms can afford heterobimetallic species in a - O-Al(C6F5)3} through the complexation-induced rotation of the N-phosphine oxide moiety, while the addition of DMAP quantitatively triggered the formation of the former complex. We experimentally and theoretically confirmed that the shape and size of the space around the Ni(0) center drastically expanded/contracted through this Lewis-acid-mediated procedure. Furthermore, a detailed discussion based on multinuclear NMR, IR absorption, and X-ray absorption spectroscopy shed light on the changes in the electronic states of the Ni centers. Thus, this work manifests a conceptually novel and effective approach to design and modulate the electronic and spatial environment surrounding metal centers in organometallic compounds using a combination of multifunctional ligands and Lewis acids.