1,5-COD(Py)(PCy3)Ir(I) Catalyst: Properties & Lab Use Guide
1,5-COD(Py)(PCy3)Ir(I) Catalyst: Properties & Lab Use Guide
1,5-Cyclooctadiene(pyridine)(tricyclohexylphosphine)iridium(I) is a well-defined iridium(I) organometallic precatalyst widely used in homogeneous hydrogenation and C–H activation research, valued for its tunable coordination environment provided by the labile cyclooctadiene, pyridine, and tricyclohexylphosphine ligands.
- CAS / SKU
- Aladdin SKU C130061
- Metal Center
- Iridium(I), d8 square-planar geometry
- Key Ligands
- 1,5-Cyclooctadiene (COD), pyridine (py), tricyclohexylphosphine (PCy3)
- Storage Conditions
- Store under inert atmosphere (N2 or Ar), cool and dry, away from moisture and air
- Primary Applications
- Precatalyst for homogeneous hydrogenation, C–H functionalization, and asymmetric catalysis studies
- Handling Class
- Air- and moisture-sensitive organometallic compound; Schlenk or glovebox technique required
Chemical Identity and Structure
1,5-Cyclooctadiene(pyridine)(tricyclohexylphosphine)iridium(I), commonly abbreviated as [Ir(COD)(py)(PCy3)], is a cationic or neutral iridium(I) square-planar complex bearing three distinct ligands: the bidentate cyclic diene 1,5-cyclooctadiene (COD), the monodentate nitrogen donor pyridine, and the bulky, electron-rich monodentate phosphine tricyclohexylphosphine (PCy3). This compound is structurally related to the celebrated Crabtree's catalyst [Ir(COD)(py)(PCy3)]PF6, sharing the same ligand set and iridium(I) oxidation state. The strong σ-donor character of PCy3 and the π-acceptor character of COD together create a metal center with distinctive electronic and steric properties that can be fine-tuned for specific catalytic tasks. The lability of the COD ligand under hydrogenation or other activating conditions is key to generating the coordinatively unsaturated active species responsible for catalytic turnover.
Handling and Safety Precautions
As an air- and moisture-sensitive organometallic iridium(I) complex, [Ir(COD)(py)(PCy3)] must be handled with rigorous exclusion of oxygen and water. The following precautions are essential:
- Inert atmosphere: All weighing, dissolution, and transfer steps should be performed inside a nitrogen- or argon-filled glovebox, or using standard Schlenk-line techniques with vacuum/inert-gas cycling.
- Solvents: Use anhydrous, degassed solvents (e.g., dry dichloromethane, THF, or toluene). Purge solvents with an inert gas for at least 20 minutes prior to use.
- Personal protection: Wear appropriate PPE including nitrile gloves, lab coat, and safety glasses. Iridium compounds should be treated as potentially hazardous; consult the SDS before use.
- Waste disposal: Collect iridium-containing waste separately for precious metal recovery in compliance with local institutional regulations.
- Storage: Seal tightly under inert gas, store at 2–8 °C or as indicated on the product label, and protect from light to prevent photodecomposition.
Do not expose the compound to prolonged ambient conditions; even brief exposure can cause partial oxidation or ligand displacement, reducing catalytic activity.
Catalytic Applications and Reaction Setup
[Ir(COD)(py)(PCy3)] serves as a versatile precatalyst in several important reaction classes:
Homogeneous Hydrogenation
When activated under hydrogen atmosphere, the COD ligand is hydrogenated and dissociates, generating a coordinatively unsaturated iridium species that can coordinate and reduce olefinic substrates. This precatalyst is particularly effective for the hydrogenation of tri- and tetrasubstituted olefins that are resistant to rhodium-based catalysts. Typical reaction conditions involve 1–5 mol% catalyst loading, H2 pressure of 1–4 atm, in dry CH2Cl2 or THF at room temperature.
C–H Activation and Functionalization
Iridium(I) complexes bearing phosphine and nitrogen ligands are well-established platforms for oxidative addition into C–H bonds, enabling borylation, silylation, and other functionalization reactions. [Ir(COD)(py)(PCy3)] may serve as a precatalyst or ligand-exchange partner in such transformations.
General Protocol Tips
- Prepare a stock solution of the catalyst in dry, degassed solvent under inert atmosphere immediately before use.
- Add substrate and any co-reagents via syringe through a rubber septum to maintain inert atmosphere integrity.
- Monitor reaction progress by TLC, GC, or NMR as appropriate.
- Quench reactions carefully; iridium can form stable hydride complexes that require specific workup procedures.
Quality Verification and Troubleshooting
To confirm the identity and purity of [Ir(COD)(py)(PCy3)] upon receipt or after prolonged storage, the following analytical methods are recommended:
- 31P NMR spectroscopy: The PCy3 ligand coordinated to iridium(I) exhibits a characteristic 31P chemical shift that distinguishes it from free phosphine and oxidized phosphine oxide. A single sharp resonance is expected for a pure, homogeneous sample.
- 1H NMR spectroscopy: COD olefinic protons and pyridine aromatic protons appear at characteristic positions; significant broadening or additional peaks may indicate decomposition or ligand exchange.
- IR spectroscopy: C=C stretching frequencies of coordinated COD are shifted relative to free COD, providing a diagnostic handle.
- Color and appearance: The compound is typically an orange to yellow crystalline or powdery solid. A color change to dark brown or black may indicate decomposition.
Common troubleshooting issues:
- Low catalytic activity: Most often caused by oxidation due to air/moisture ingress. Ensure strict inert-atmosphere technique and use freshly opened or freshly prepared catalyst solutions.
- Insolubility: If the complex does not dissolve readily, gentle warming (≤40 °C) under inert atmosphere with stirring may help; avoid prolonged heating.
- Unexpected byproducts: Check solvent purity and dryness; trace water or oxygen can alter selectivity.
Frequently asked questions
What is the relationship between [Ir(COD)(py)(PCy3)] and Crabtree's catalyst?
Crabtree's catalyst is [Ir(COD)(py)(PCy3)]PF6, an ionic complex where the iridium center carries a positive charge balanced by the non-coordinating hexafluorophosphate counterion. The neutral or differently salt-paired form [Ir(COD)(py)(PCy3)] shares the same inner-sphere ligand set and iridium(I) core. Both are precatalysts for homogeneous hydrogenation, but solubility, activation behavior, and exact reactivity can differ depending on the counterion and reaction medium.
How should I activate [Ir(COD)(py)(PCy3)] for a hydrogenation reaction?
Dissolve the complex in dry, degassed solvent under inert atmosphere to prepare a stock solution. Transfer the desired amount to your reaction vessel containing substrate, then expose the sealed vessel to H2 at the desired pressure (typically 1–4 atm). Under H2, the COD ligand is selectively hydrogenated to cyclooctane and dissociates, generating the active iridium hydride or coordinatively unsaturated species responsible for substrate hydrogenation. No separate pre-activation step is usually required.
What solvents are compatible with [Ir(COD)(py)(PCy3)]?
The complex is generally soluble in common organic solvents such as dichloromethane, chloroform, THF, acetone, and toluene. All solvents must be rigorously dried and degassed prior to use to prevent deactivation of the catalyst by moisture or dissolved oxygen. Protic solvents such as water, methanol, or ethanol are generally incompatible due to potential ligand displacement and decomposition of the iridium complex.
How do I confirm that my sample of [Ir(COD)(py)(PCy3)] has not decomposed during storage?
Visual inspection for color change (from orange-yellow to dark brown or black) provides a quick initial check. Definitive confirmation should be obtained by 31P NMR, which shows a characteristic sharp resonance for the intact complex distinct from free PCy3 or its oxide, and by 1H NMR to confirm the presence of COD olefinic and pyridine aromatic signals. Significant broadening, new peaks, or loss of expected resonances indicates decomposition.
References
- Crabtree, R. H. The organometallic chemistry of the transition metals. Wiley, 7th ed. (textbook reference for Ir(I) square-planar complexes and Crabtree's catalyst).
- Crabtree, R. H. Iridium compounds in catalysis. Accounts of Chemical Research, 1979. (Original literature describing Ir(COD)(py)(PCy3) complexes in homogeneous hydrogenation).
- Hartwig, J. F. Organotransition Metal Chemistry: From Bonding to Catalysis. University Science Books, 2010. (General reference for iridium-catalyzed C-H functionalization and hydrogenation mechanisms).
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