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Patent landscape, scope, and claims: |
US Patent 5,969,166: Scope, claim architecture, and US landscape for Ru/Mo oxo-ligand catalysts for selective epoxidation/oxidation
US 5,969,166 is directed to ruthenium or molybdenum oxo-ligand complexes used as catalysts for selective olefin epoxidation (and, in an independent claim, selective olefin oxidation) using oxygen (including atmospheric oxygen). The claim set is built around (i) a narrow metal-core stoichiometry constraint that enforces an average metal oxidation state of +6 through a coupled choice of indices x, y, z, (ii) a ligand class restricted to N/O/S donor ligands derived from specified precursor formulas in the Mo case, and (iii) an activity-and-performance gate requiring selectivity thresholds by metal identity. Dependent claims add operational windows (temperature, pressure, solvent/no solvent) and an explicit donor-ligand exemplified by specific pyridyl/thiophenyl/pyrrolyl/imidazole-substituted alcohol precursors.
What is the invention’s claim core and how is it legally bounded?
Independent claims map to two catalyst embodiments and two independent routes
The patent includes two independent catalyst claims and two independent process claims:
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Claim 1 (catalyst for selective epoxidation)
“A compound of the formula (1)” defined by indices x, y, z, with M = Ru or Mo, L = N/O/S donor ligand, and selectivity thresholds:
- Selectivity > 45% if Mo
- Selectivity ≥ 30% if Ru
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Claim 2 (heterogeneous catalyst for selective oxidation of olefins in presence of oxygen)
Same formula (1) complex plus an explicit support material list. The performance threshold is stated for oxidation (Mo >45%, Ru not explicitly set in the provided Claim 2 excerpt beyond “more than 45% if a molybdenum compound is used”).
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Claim 5 (process for selective epoxidization using only atmospheric oxygen)
Covers epoxidation of a broad olefin substrate class under oxygen-from-air constraints, catalyzed by the same formula (1) complexes, with selectivity thresholds and a ligand-derived Mo proviso.
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Claim 6 (process dependent on donor ligand derived from specific alcohol precursors)
Narrows ligand selection to a defined set of “donor ligand” precursors (1-(2-pyridyl)-substituted methanol/cyclohexanol motifs; 2-thiophenyl; 2-pyrrolyl; 2-imidazole; including perfluoroalkyl variants).
Legal bounding mechanisms
The independent claims are bounded by three coupled constraints:
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Metal-oxo stoichiometry constraint (indices x, y, z)
- x = 1 to 3
- z = 2 to 2x
- y = 1 to 2x+1, chosen so that x + z gives a metal oxidation number of +6
This is not a simple “range” claim; it is a constraint tying together x and z to enforce formal +6 oxidation state.
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Ligand class constraint (N/O/S donors, with a Mo-specific derivation proviso)
- L is N/O/S donor ligand (Ru or Mo case)
- Mo proviso: if M = Mo, then L must be derived from compounds of formulas (2), (3), or (4), where the general structure includes:
- X = N, O or S
- X' = N or C
- R1 and R2 each independently are branched/unbranched optionally halogenated C1-C12 alkyl, or optionally substituted C6-C14 aryl/heteroaryl, or together form C═O or C═S, or R1 or R2 = H.
This proviso is a major narrowing element for Mo: a competitor using different Mo ligand systems may avoid literal claim 1/5 even if they hit Ru ranges.
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Performance gate (selectivity thresholds keyed to metal identity)
- Claim 1: selectivity >45% for Mo, ≥30% for Ru
- Claim 5: ≧40% for Mo, ≧30% for Ru
These thresholds convert the claim from purely structural to structural-plus-functional. In litigation, that creates a factual battleground (how selectivity is measured, which products counted as “epoxide,” and under what conditions).
How broad is the catalyst formula coverage?
Formula (1) index ranges
The claim defines the catalyst class as:
- M = Ru or Mo
- L = N/O/S donor ligand
- Complex formula: M_x O_y (L)_z
- x ∈ [1,3]
- z ∈ [2, 2x]
- y ∈ [1, 2x+1], selected so that x+z corresponds to metal oxidation number +6
Practical read-through:
The claim allows multiple stoichiometries and coordination numbers via x and z. Because y is adjusted to meet a +6 oxidation condition, the allowed combinations are interdependent rather than freely chosen.
Ru vs Mo ligand flexibility
- Ru: L can be any N/O/S donor ligand that fits the formula framework (no additional “derived-from (2)/(3)/(4)” proviso stated for Ru in the provided claims).
- Mo: the ligand must be derived from specified precursor formulas. This is a narrower Mo sub-class.
Solubility carve-in (Claim 3 and Claim 12)
- Claim 3 and Claim 12 both require the formula (1) compound is “readily soluble in organic solvents.”
In enforcement terms, that can narrow to complexes that meet solubility behavior in common solvent systems used for epoxidation.
What substrates and conditions does the process claim cover?
Substrate scope
Claim 5 defines epoxidizable olefins by a general substrate formula (not reproduced in full in the excerpt), plus broader scope in dependent claims:
- Claim 7: “aliphatic, optionally branched C2-C30 olefin or alicyclic C5-C12 olefin”
That breadth is substantial and covers most industrially relevant alkene families.
Oxidant scope
Claim 5: “with only atmospheric oxygen as the oxidizing agent”
Claim 8: oxygen “used in the pure form or is diluted with an inert gas.”
So the oxidant is oxygen, but at minimum atmospheric oxygen is explicitly required for Claim 5.
Temperature and pressure
Claim 9:
- 30 to 300°C for oxidation of C6-C12 alkenes
- 120 to 230°C for oxidation of C2-C5 alkenes
- Pressure selected so reaction proceeds in the liquid phase.
Solvent/no solvent
- Claim 10: without solvent, in the pure olefin
- Claim 11: solvent selected from:
- halogenated aromatics
- halogenated or non-halogenated hydrocarbons
- C1-C12 alcohols
- water
This creates multiple infringement pathways: even if a process uses a typical organic medium, Claim 11 can be implicated.
How does the heterogeneous-catalyst claim expand or change risk?
Claim 2 adds a support material layer:
- The catalyst comprises formula (1) complex plus an inorganic or organic support material.
- Supports listed (from the excerpt) include:
- oxides: aluminum oxide, silicon dioxide, alumosilicates, titanium dioxide, zirconium dioxide, thorium dioxide, lanthanum oxide, magnesium oxide, calcium oxide, barium oxide, tin oxide, cerium dioxide, zinc oxide, boron oxide, boron nitride, boron carbide, boron phosphate, zirconium phosphate, silicon nitride, silicon carbide
- organic polymers: “polypyridines or polyacrylates” (as stated)
For landscape analysis, Claim 2 increases the set of potentially infringing commercial catalyst formats, including supported metal-oxo/ligand systems and polymer-supported architectures.
What ligand families are singled out in the dependent claims?
Claim 6: explicit donor-ligand precursors
Claim 6 narrows ligand selection to complexes derived from donor ligand precursors:
- 1,1-(C1-C6)-alkyl-1-(2-pyridyl)methanol
- 1-(2-pyridyl)-cyclohexan-1-ol
- 1-phenyl-1-(2-pyridyl)methanol
- 1,1-(C1-C6)-alkyl-1-(2-thiophenyl)methanol
- 1,1-(C1-C6)-perfluoroalkyl-1-(2-thiophenyl)methanol
- 1,1-(C1-C6)-alkyl-1-(2-pyrrolyl)methanol
- 1,1-(C1-C6)-alkyl-1-(2-imidazole)methanol
- 1,1-(C1-C6)-perfluoroalkyl-1-(2-imidazole)methanol
This is a targeted “ligand derivation” list that can be used in freedom-to-operate (FTO) when an Mo catalyst uses those ligand scaffolds.
Scope comparison: epoxidation vs oxidation
Performance gates and claim positioning
- Claim 1 is tied to “selective epoxidization” with selectivity thresholds by metal.
- Claim 2 is tied to “selective oxidation of olefins in the presence of oxygen” with selectivity threshold stated for Mo.
- Claim 5 is epoxidation under “only atmospheric oxygen,” with selectivity thresholds (Mo at least 40%, Ru at least 30%).
- Dependent claims (7-11) further shape reaction engineering (temperature, pressure for liquid phase, solvent/no solvent).
Implication for landscape
A competitor can attempt to design around by:
- aiming at oxidative transformation where “epoxidization” is not the targeted product definition for selectivity measurement, or
- using oxygen sources not restricted to atmospheric oxygen (but note Claim 5 is process-specific; Claim 1/2 remain catalyst claims).
The cleanest design-around is usually ligand-system engineering (especially Mo derived-from constraints) or stoichiometry/oxidation state constraints for x/y/z.
Patent landscape analysis approach (US 5,969,166 as the anchor)
Because the claims are structural-plus-functional, the landscape is not limited to identical formula hits. Relevant prior art and potential white-space tend to cluster around:
- Ru/Mo oxo- or polyoxometal-like epoxidation catalysts with N/O/S ligands
- Selective epoxidation under oxygen (including air)
- Heterogeneous supported Ru/Mo catalysts using oxide or polymer supports
- Ligand chemistry for Mo systems derived from the specified precursor family
In practice, competitive products and academic work often use:
- Ru-based peroxo/oxo intermediates with N-donor ligands
- Mo-based oxo catalysts stabilized by nitrogen/oxygen donor ligands
The decisive factor for claim literal coverage in US 5,969,166 is not merely “Ru or Mo” but whether the catalyst can be mapped into M_x O_y (L)_z with the x+z => +6 oxidation state rule and meets the selectivity thresholds.
Claim chart style breakdown (for infringement mapping)
Core elements for Claim 1 (epoxidation catalyst)
| Element |
Claim requirement |
Scope effect |
| Catalyst composition |
Compound formula (1): M_x O_y (L)_z |
Structural basis |
| Metal |
M = Ru or Mo |
Two-metal fork |
| Indices |
x=1-3; z=2-2x; y=1-2x+1, chosen so x+z = +6 metal oxidation |
Coupled stoichiometry constraint |
| Ligand type |
L = N/O/S donor ligand |
Donor chemistry restriction |
| Mo ligand proviso |
If Mo: L derived from formulas (2)/(3)/(4) with X/X' and R1/R2 rules |
Major Mo narrowing |
| Performance threshold |
Selectivity >45% (Mo) or ≥30% (Ru) |
Functional limitation |
Core elements for Claim 5 (epoxidation process)
| Element |
Claim requirement |
Scope effect |
| Substrate |
Epoxidize alkenes defined in claim 5; Claim 7 expands to C2-C30 aliphatic and C5-C12 alicyclic olefins |
Broad substrate class |
| Oxidant |
Only atmospheric oxygen |
Process-specific |
| Catalyst |
formula (1) complex with Mo ligand proviso |
Matches Claim 1 architecture |
| Performance threshold |
≧40% (Mo); ≧30% (Ru) |
Functional limitation |
| Operational constraints (dependent) |
temperature windows, liquid-phase pressure, solvent/no solvent |
Additional design constraints |
Core elements for Claim 2 (heterogeneous oxidation catalyst)
| Element |
Claim requirement |
Scope effect |
| Catalyst |
support + formula (1) complex |
Formats enabled |
| Support list |
Oxides, phosphate, nitride/carbide, polypyridines, polyacrylates |
Limits support types |
| Performance |
Selectivity for oxidation: Mo >45% |
Functional limitation |
Where infringement risk is highest in real-world process development
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Ru or Mo catalyst targeting air-based epoxidation where selectivity exceeds the claim gates
- If selectivity is demonstrated above the thresholds, the performance gates do not help avoidance.
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Mo catalysts using ligand precursors in Claim 6’s family
- These ligand precursors correspond to the Mo “derived-from” constraint and are likely close to exemplified working embodiments.
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Supported catalysts using oxide or polymer supports listed in Claim 4
- Commercial catalyst immobilization often uses alumina/silica or similar oxides, which are explicitly covered.
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Processes where oxygen source is air and runs in liquid phase
- Liquid-phase operation is addressed by Claim 9, and air oxidant by Claim 5.
Key Takeaways
- US 5,969,166 is centered on Ru/Mo N/O/S donor ligand oxo complexes defined by M_x O_y (L)_z with a coupled x+z rule to enforce a +6 metal oxidation state and selectivity thresholds tied to metal identity.
- Claim 5 anchors the process to epoxidation using only atmospheric oxygen, with broad olefin substrate coverage (expanded to C2-C30 aliphatic and C5-C12 alicyclic) and engineering windows (temperature, liquid-phase pressure, solvent/no solvent).
- Mo ligand architecture is materially narrower than Ru: for Mo, L must be derived from specified precursor formulas and is exemplified in Claim 6 with pyridyl/thiophenyl/pyrrolyl/imidazole-containing alcohol precursors.
- Heterogeneous risk is amplified by Claim 2/4 because the support materials include common oxide supports (silica, alumina, titania, zirconia, etc.) and polymer supports (polypyridines, polyacrylates).
FAQs
1) Does the patent require a specific oxidant besides atmospheric oxygen?
Claim 5 requires “only atmospheric oxygen” for the epoxidation process, while dependent Claim 8 allows oxygen in pure form or diluted with inert gas.
2) How can a competitor avoid literal scope?
The most direct literal escape routes are to (i) use Ru or Mo catalysts that do not fit the M_x O_y (L)_z stoichiometry with the x+z => +6 constraint, (ii) for Mo, avoid ligands that are derived from the specified Mo precursor formulas, or (iii) operate outside the epoxidation selectivity thresholds.
3) Is “selectivity” a structural limitation or a performance limitation?
It is a performance limitation embedded in the claims: Claim 1 and Claim 5 require selectivity thresholds that depend on whether Mo or Ru is used.
4) Does the patent cover supported catalysts?
Yes. Claim 2 covers heterogeneous catalysts comprising support material selected from the enumerated list in Claim 4.
5) Are only terminal alkenes covered?
No. Claim 7 covers broad olefins including branched aliphatic C2-C30 olefins and alicyclic C5-C12 olefins.
References
[1] US Patent 5,969,166.
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