Ruthenium Oxidation States
Reference for all known oxidation states of ruthenium (Ru, Z=44), its electron configuration, and representative compounds for each state.
Use the Ruthenium Oxidation States
Atomic #
44
Ru
Ruthenium
Atomic Mass
101.07 u
Group
8
Period
5
Block
d-block
Electronegativity
2.2 (Pauling)
Oxidation States
−2 to +8
Ruthenium is among the most oxidation-state-versatile transition metals, spanning −2 through +8. The ground-state configuration is [Kr] 4d7 5s1 — eight valence electrons that can be progressively removed or formally donated. The most practically important states are +2, +3, and +4, though the remarkable +8 state in RuO4 demonstrates the full reach of 4d bonding.
| Oxidation State | Stability | Notes |
|---|---|---|
| +8 | Rare but isolable | Found in RuO4, a volatile yellow solid (bp 40 °C). Powerful oxidizer. All eight 4d/5s electrons are formally engaged in Ru=O bonds. |
| +7 | Rare | Known in the perruthenate ion [RuO4]−. Less stable than RuO4; the anion is a strong oxidizer used in organic synthesis. |
| +6 | Moderate | Seen in ruthenate(VI) salts (RuO42−). Isolable under alkaline conditions. Strong oxidizing agent. |
| +5 | Uncommon | Found in RuF5 (pentafluoride) and a few oxide-fluoride species. Not common in aqueous chemistry. |
| +4 | Common | Stable in RuO2 (rutile structure, electrically conductive oxide used in electrodes) and RuF4. Accessible and well-characterized. |
| +3 | Common | The most common Ru state in simple halide salts — RuCl3 is the main commercial precursor. Also abundant in coordination complexes. |
| +2 | Common | Dominant in organometallic and coordination chemistry. [Ru(bpy)3]2+ (bpy = 2,2′-bipyridyl) is the archetypal Ru(II) photosensitizer. Strong π-back-donation stabilizes low oxidation states. |
| +1 | Rare | Observed in Ru(I) carbonyl and organometallic clusters. Not common in simple ionic chemistry; stabilized by strong-field ligands (CO, NO). |
| 0 | Elemental / complexes | Bulk ruthenium metal. Also Ru(0) in carbonyl clusters such as Ru3(CO)12. |
| −1 | Very rare | Observed in electron-rich metal carbonyl anion clusters under reducing conditions. Formal assignment; actual electron density delocalized. |
| −2 | Very rare | Proposed in some anionic carbonylate complexes ([Ru(CO)4]2−). Requires strong π-donor ligands and highly reducing conditions. |
Key ionization energies
IE1 = 710.2 kJ/mol | IE2 = 1620 kJ/mol | IE3 = 2747 kJ/mol
The relatively low IE1 (vs. 3d metals) reflects the more diffuse 4d/5s orbitals, enabling stable high oxidation states through strong covalent M=O bonds.
IE1 = 710.2 kJ/mol | IE2 = 1620 kJ/mol | IE3 = 2747 kJ/mol
The relatively low IE1 (vs. 3d metals) reflects the more diffuse 4d/5s orbitals, enabling stable high oxidation states through strong covalent M=O bonds.
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Summary
Reference for all known oxidation states of ruthenium (Ru, Z=44), its electron configuration, and representative compounds for each state.
How it works
- Click a tab — Oxidation States, Compounds, Electron Config, or Physical Props — to explore each area.
- The Oxidation States panel lists every known state from −2 to +8 with stability ratings and chemical context.
- The Compounds panel shows representative ruthenium compounds with formulas and Ru oxidation assignments.
- The Electron Config panel displays the 4d orbital filling and ionization context.
- The Physical Props panel provides atomic and bulk material data.
- Click any monospace table cell to copy its value to your clipboard.
Use cases
- Students and researchers studying 4d transition metal chemistry.
- Chemists designing catalysts involving ruthenium complexes.
- Materials scientists working with ruthenium-based coatings or electrodes.
- Educators preparing lessons on transition metal oxidation state diversity.
- Anyone needing a quick reference for ruthenium compound oxidation assignments.
Frequently Asked Questions
Last updated: 2026-09-24 ·
Reviewed by Nham Vu