Co K-edge XAS measurements were performed to characterize the vacant Co-based valence electronic structure (Figure ). Our analysis focuses on the pre-edge region, where transitions arise from electronic excitations into the vacant Co-based valence acceptor orbitals. 1 and 2 exhibit a pre-edge feature that is well-separated from other rising edge contributions and is consistent with Co 2+ in a tetrahedral coordination environment. Deconvolution reveals that the pre-edge for each spectrum is composed of an intense feature at 7709.3 eV, with greater intensity for 2 than 1, and a low-intensity shoulder at ~7711.4 eV (Figure , Table ). In 3 and 4, the pre-edge features occur ~2 eV higher in energy and overlap significantly with other risingedge contributions, limiting our ability to quantify differences in energy and intensity. Therefore, high energy resolution fluorescence detected (HERFD) XAS data were measured to better resolve the pre-edge features (Figure ). HERFD-XAS probes a limited "diagonal" cut of the 1s2p resonant inelastic X-ray scattering (RIXS) plane. This technique enables core-hole broadening to be suppressed, leading to dramatically improved energy resolution compared to conventional XAS. However, off-diagonal features in the RIXS plane are not captured, which can lead to intensity differences compared to conventional XAS. While the intensity mechanisms are not directly comparable, the HERFD-XAS data for 1 -4 show similar energy and intensity trends to the standard XAS measurements, indicating that a significant fraction of the contribution to the standard XAS is captured in the HERFD-XAS. The low-energy transitions for 3 and 4 are better resolved in the HERFD-XAS data. The HERFD-XAS pre-edge regions were deconvoluted to identify dominant contributions to the observed spectral shapes (Figure , Table ). The HERFD-XAS pre-edge of 3 (4) shows an intense feature at 7710.8 eV (7710.5 eV) and a low-energy, weak intensity tail. These features were used as a guide to deconvolute the standard Co K-pre-edges. In 3 and 4, the highest intensity pre-edge transition appears at ~7710.8 eV, 1.5 eV higher than the most intense pre-edge feature in 2 (Note: we are careful to not refer to this energy difference as a "peak shift" because the features in 1 and 2 originate from different transitions than those in 3 and 4, as will be discussed below). The Co K-pre-edges for 3 and 4 also show low-intensity features at 7709.3 eV in both compounds. Co-ligand bonding interactions were further investigated using Co Kβ valence-to-core (v2c) XES (Figure ). The spectra of 1 and 2 exhibit broad features at ~7703-7706 eV and a lowenergy tail at ~7699 eV, with no significant differences between these compounds. In contrast, the spectra for 3 and 4 are much more intense. Deconvolution of the spectra reveals strong contributions from features at ~7705.5 eV, ~7703.0 eV, and ~7699.9 eV (Figure , Table ).