[1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]bis(2-bromopyridine)dichloro(phenylmethylene)ruthenium
[CAS# 900169-53-1]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate >> Pyridine compound >> Benzylpyridine
• Name: [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]bis(2-bromopyridine)dichloro(phenylmethylene)ruthenium
• Synonyms: Grubbs Catalyst(TM) C884
• Molecular Formula: C₃₈H₄₀Br₂Cl₂N₄Ru
• Molecular Weight: 884.53
• CAS Registry Number: 900169-53-1
• SMILES: Brc1cccnc1.Brc1cccnc1.Cl[Ru](Cl)(=C3N(c1c(cc(cc1C)C)C)CCN3c2c(cc(cc2C)C)C)=Cc4ccccc4

Properties

• Melting point: 140 °C (Decomposes) (Expl.)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H315-H319-H335
• Safety Statements: P261-P305+P351+P338

Discovery and Applications

[1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]bis(2-bromopyridine)dichloro(phenylmethylene)ruthenium is a ruthenium-based organometallic complex that belongs to a class of olefin metathesis catalysts commonly referred to as second-generation Grubbs-type catalysts bearing N-heterocyclic carbene ligands. The compound contains a ruthenium center coordinated to a phenylmethylene group, two chloride ligands, two 2-bromopyridine ligands, and an N-heterocyclic carbene derived from 1,3-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene. The development of such complexes followed the discovery that ruthenium carbene species are capable of catalyzing carbon–carbon double bond metathesis reactions under relatively mild conditions.

The discovery of well-defined ruthenium alkylidene catalysts in the 1990s represented a major advance in synthetic chemistry. Earlier heterogeneous and ill-defined systems had demonstrated olefin metathesis activity, but the isolation of stable, structurally characterized ruthenium carbene complexes enabled more predictable and versatile applications. The introduction of N-heterocyclic carbene ligands further improved catalyst stability and activity. These ligands donate strong electron density to the metal center, enhancing both initiation rates and resistance to decomposition. Complexes incorporating bulky aryl-substituted N-heterocyclic carbenes, such as the 1,3-bis(2,4,6-trimethylphenyl) derivative, were shown to display high activity in a range of metathesis transformations.

The specific complex described, featuring bis(2-bromopyridine) ligands in addition to the dichloro and phenylmethylene groups, is part of a family of modified ruthenium catalysts designed to fine-tune reactivity and stability. The coordination of substituted pyridine ligands has been used to influence initiation kinetics and catalyst lifetime. Structural characterization by X-ray crystallography has confirmed the square-pyramidal or distorted octahedral coordination environment typical of these ruthenium alkylidene complexes.

In practical application, ruthenium carbene complexes of this type have been employed in ring-closing metathesis, cross metathesis, and ring-opening metathesis polymerization. These reactions enable the formation of carbon–carbon double bonds with high functional group tolerance. The catalysts operate in the presence of a wide variety of substituents, including esters, amides, and heterocycles, which distinguishes them from earlier metathesis systems that were more sensitive to functional groups. As a result, they have been used extensively in academic and industrial laboratories for the synthesis of cyclic compounds, fine chemicals, and advanced materials.

The broader class of ruthenium N-heterocyclic carbene metathesis catalysts has also played a role in polymer chemistry. Ring-opening metathesis polymerization mediated by such complexes allows the preparation of well-defined polymers from strained cyclic olefins. Control over molecular weight and polymer architecture has been achieved through careful selection of catalyst structure and reaction conditions. The robustness of these catalysts under ambient conditions has contributed to their widespread adoption.

The development and application of ruthenium carbene catalysts, including complexes bearing 1,3-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene ligands, were recognized as major milestones in synthetic methodology. Their discovery transformed olefin metathesis into a reliable and broadly applicable tool for constructing carbon–carbon double bonds. The compound described represents a structurally defined member of this well-documented family, combining a ruthenium alkylidene core with an N-heterocyclic carbene and ancillary ligands designed to optimize catalytic performance in established metathesis reactions.

References

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