In order to characterize the local geometry around the Co-centers of complexes 1-4, as well as to probe the cobalt oxidation states, we performed Co K-edge XAS measurements (Figure ). The absorption spectra of 1 and 2 exhibit a pre-edge peak at 7709.3 eV that is well-separated from higher energy rising-edge contributions. This feature arises from Co 1s → 3d transitions, which are quadrupole-allowed but dipole-forbidden. However, due to 3d-4p hybridization, this feature gains a normalized intensity of 0.1-0.15, which is consistent with tetrahedrally-coordinated Co species that lack cetrosymmetry. Moreover, the energy of this feature is consistent with Co 2+ species, confirming the formal Co oxidation state in compounds 1 and 2. The pre-edge transitions in 3 and 4 appear at higher energies (7709.3 -7713.0 eV) and overlap with other contributions to the rising edge absorption spectra. However, the spectra of 3 and 4 exhibit no consistent red-or blue-shift along the absorption edge relative to those of 1 and 2, and as a result, the Co oxidation state in these compounds cannot be readily determined. An in-depth study on the detailed electronic structure and Co-ligand bonding information contained in the Co K-edge XAS spectra is reported separately. In NMR, complex 4 is very similar to 3, however, to obtain more structural information the Co-edge EXAFS spectra of these complexes were analyzed. The Fourier transform EXAFS of 3 (Figure ) shows intense scattering features between 1-2.5 Å (not phaseshift corrected). The data were modeled well by 1 Co-N at 2.00 ± 0.02 Å, 1 Co-P at 2.14 ± 0.03 Å, 1 Co-Si at 2.20 ± 0.03 Å, and 1 Co-Si at 2.31 ± 0.03 Å, which is consistent with the X-ray crystal structure (Figure ). In addition, the Co-Co distance in 3 was fit to 2.51 ± 0.02 Å which is in excellent agreement with the value of 2.5172(6) Å in the X-ray crystal structure. Finally, a low-intensity multiple scattering contribution from Co-Co-P was successfully modeled at 4.49 ± 0.04, confirming the bimetallic structure of the complex and the nearly linear P-Co-Co-P moiety.