We present a comprehensive spectroscopic mapping of phonon, magnetic, electron-hole, and spin-orbit (SO) excitonic excitations across the insulator-to-metal transition (IMT) in the solid solution $\mathrm{Ru}{\left({\mathrm{Br}}_{1-x}{\mathrm{I}}_x\right)}_3$ using Raman spectroscopy. This material series offers a unique platform to explore SO-entangled magnetism, bridging the SO-assisted Mott insulator ${\mathrm{RuBr}}_3$ and the correlated semimetal ${\mathrm{RuI}}_3$. With increasing iodine content, we observe a systematic softening of phonon modes, suppression of the zigzag antiferromagnetic order, and a gradual dominance of electron-hole excitations over SO excitons. For $x\ge 0.6$, two-magnon Raman scattering is suppressed, while an electron-hole continuum emerges above $x\approx 0.85$, coinciding with the IMT threshold. Remarkably, ${\mathrm{RuI}}_3$ displays a weakly increasing $\omega$ dependence of its Raman response and power-law growth of the dynamic Raman susceptibility, indicative of a spin-liquid-like behavior. Theoretical modeling corroborates the persistence of $j_{\text{eff}}=\frac{1}{2}$ moments on the metallic side, despite partial electronic delocalization. Our results provide insights into the interplay between SO coupling, electronic correlations, and structural distortions in collectively driving the IMT in SO-entangled systems.

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• Magnetic interactions
• Magnetic phase transitions
• Metal-insulator transition
• Spin dynamics
• Spin-orbit coupling
• Spin-phonon coupling
• Mott insulators
• Kitaev model
• Many-body techniques
• Raman spectroscopy