Carbonylbis(triphenylphosphine)rhodium(I) chloride
[CAS# 13938-94-8]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic rhodium
• Name: Carbonylbis(triphenylphosphine)rhodium(I) chloride
• Synonyms: Bis(triphenylphosphine)rhodium(I) carbonyl chloride
• Molecular Formula: C₃₇H₃₀ClOP₂Rh
• Molecular Weight: 690.95
• CAS Registry Number: 13938-94-8
• EC Number: 237-712-8
• SMILES: [C-]#[O+].C1=CC=C(C=C1)P(C2=CC=CC=C2)C3=CC=CC=C3.C1=CC=C(C=C1)P(C2=CC=CC=C2)C3=CC=CC=C3.[Cl-].[Rh]

Properties

• Melting point: 224 - 227 °C (Decomposes) (Expl.)
• Solubility: Soluble (acetone, chloroform, ethano)l (Expl.)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H312-H315-H319-H332-H335-H413
• Safety Statements: P261-P264-P264+P265-P270-P271-P273-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P317-P319-P321-P330-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Acute toxicity	Acute Tox.	4	H302

Discovery and Applications

Carbonylbis(triphenylphosphine)rhodium(I) chloride, commonly abbreviated as RhCl(CO)(PPh₃)₂, is a coordination complex of rhodium featuring rhodium in the +1 oxidation state. The compound consists of a rhodium(I) center coordinated by a carbonyl (CO) ligand, two triphenylphosphine (PPh₃) ligands, and a chloride ion. It typically appears as a yellow to orange crystalline solid and is soluble in common organic solvents.

The synthesis of carbonylbis(triphenylphosphine)rhodium(I) chloride usually involves the reaction of rhodium(III) chloride hydrate with an excess of triphenylphosphine under a carbon monoxide atmosphere. This reduction process leads to the formation of the rhodium(I) complex. The reaction is often carried out in solvents like ethanol or acetone, and the product can be isolated by crystallization.

Structurally, the rhodium center in RhCl(CO)(PPh₃)₂ adopts a square planar geometry, characteristic of d⁸ transition metal complexes. The coordination sphere includes one carbonyl ligand, two triphenylphosphine ligands, and one chloride ligand. The carbonyl ligand binds through the carbon atom with a strong metal-to-ligand backbonding interaction, while the phosphines coordinate via phosphorus atoms. The chloride ion serves as a monodentate ligand completing the coordination environment.

This complex is well-known for its role as a catalyst precursor in homogeneous catalysis, especially in hydroformylation reactions. Hydroformylation, also called the oxo process, involves the addition of a formyl group and hydrogen to alkenes, producing aldehydes that are valuable intermediates in the manufacture of plastics, detergents, and other chemicals. RhCl(CO)(PPh₃)₂ is converted under reaction conditions into active catalytic species that enable high activity and selectivity.

Besides hydroformylation, carbonylbis(triphenylphosphine)rhodium(I) chloride is employed in other catalytic processes, such as hydrogenation and carbonylation reactions. Its well-defined structure and ligand environment allow fine-tuning of catalytic properties by modifying phosphine ligands or reaction parameters.

The complex is also of interest in organometallic and coordination chemistry research, serving as a model compound for studying metal-ligand bonding, reaction mechanisms, and electronic properties of rhodium complexes. Its relatively straightforward synthesis and stability facilitate such studies.

Handling of RhCl(CO)(PPh₃)₂ requires standard precautions typical for organometallic complexes. It should be stored under inert atmosphere or in a dry environment to prevent degradation. The compound and its solutions should be handled in a fume hood due to potential toxicity and volatility of carbon monoxide.

In summary, carbonylbis(triphenylphosphine)rhodium(I) chloride is a square planar rhodium(I) complex coordinated by carbonyl, two triphenylphosphine ligands, and chloride. It is synthesized by reduction of rhodium(III) chloride with triphenylphosphine under CO atmosphere and serves as an important catalyst precursor, especially in hydroformylation. Its well-characterized structure and catalytic utility make it a valuable compound in both industrial and academic chemistry.

References

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