Wilkinson's catalyst

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Wilkinson's catalyst
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Names
IUPAC name
(SP-4)-chlorido­tris(triphenylphosphene)­rhodium
Other names
Rhodium(I) tris(triphenylphosphene) chloride,
Wilkinson's catalyst,
Tris(triphenylphosphene)­rhodium(I) chloride
Identifiers
3D model (JSmol)
ECHA InfoCard 100.035.207 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 238-744-5
PubChem CID
RTECS number
  • none
UNII
  • InChI=1S/3C18H15P.ClH.Rh/c3*1-4-10-16(11-5-1)19(17-12-6-2-7-13-17)18-14-8-3-9-15-18;;/h3*1-15H;1H;/p-1
    Key: QBERHIJABFXGRZ-UHFFFAOYSA-M
  • Cl[Rh-3]([P+](c0ccccc0)(c0ccccc0)c0ccccc0)([P+](c0ccccc0)(c0ccccc0)c0ccccc0)[P+](c0ccccc0)(c0ccccc0)c0ccccc0
Properties
C54H45ClP3Rh
Molar mass 925.22 g/mol
Appearancered solid
Melting point 245 to 250 °C (473 to 482 °F; 518 to 523 K)
insoluble in water
Solubility in other solvents20 g/L (CHCl3, CH2Cl2), 2 g/L (benzene, toluene) [1]
Structure
square planar d8 (diamagnetic; sp2d-hybridized)
Hazards [2]
Occupational safety and health (OHS/OSH):
Main hazards
none
GHS labelling:
GHS-pictogram-exclam.svg
Warning
H302, H317, H413
P261, P264, P270, P272, P273, P280, P301+P312, P302+P352, P330, P333+P313, P363, P501
Related compounds
Related compounds
 triphenylphosphene
Pd(PPh3)4
IrCl(CO)[P(C6H5)3]2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Wilkinson's catalyst (chlorido­tris(triphenylphosphine)­rhodium(I)) is a coordination complex of rhodium with the formula [RhCl(PPh3)], where 'Ph' denotes a phenyl group. It is a red-brown colored solid that is soluble in hydrocarbon solvents such as benzene, and more so in tetrahydrofuran or chlorinated solvents such as dichloromethane. The compound is widely used as a catalyst for hydrogenation of alkenes. It is named after chemist and Nobel laureate Sir Geoffrey Wilkinson, who first popularized its use.

Historically, Wilkinson's catalyst has been a paradigm in catalytic studies leading to several advances in the field such as the implementation of some of the first heteronuclear magnetic resonance studies for its structural elucidation in solution (31P), [3] parahydrogen-induced polarization spectroscopy to determine the nature of transient reactive species, [4] or one of the first detailed kinetic investigation by Halpern to elucidate the mechanism. [5] Furthermore, the catalytic and organometallic studies on Wilkinson's catalyst also played a significant role on the subsequent development of cationic Rh- and Ru-based asymmetric hydrogenation transfer catalysts which set the foundations for modern asymmetric catalysis. [6]

Structure and basic properties

According to single crystal X-ray diffraction the compound adopts a slightly distorted square planar structure. [7]

In analyzing the bonding, it is a complex of Rh(I), a d8 transition metal ion. From the perspective of the 18-electron rule, the four ligands each provides two electrons, for a total of 16-electrons. As such the compound is coordinatively unsaturated, i.e. susceptible to binding substrates (alkenes and H2). In contrast, IrCl(PPh3)3 undergoes cyclometallation to give HIrCl(PPh3)2(PPh2C6H4), a coordinatively saturated Ir(III) complex that is not catalytically active. [8]

Synthesis

Wilkinson's catalyst is usually obtained by treating rhodium(III) chloride hydrate with an excess of triphenylphosphine in refluxing ethanol. [9] [10] [1] Triphenylphosphine serves as both a ligand and a two-electron reducing agent that oxidizes itself from oxidation state (III) to (V). In the synthesis, three equivalents of triphenylphosphine become ligands in the product, while the fourth reduces rhodium(III) to rhodium(I).

RhCl3(H2O)3 + 4 PPh3 → RhCl(PPh3)3 + OPPh3 + 2 HCl + 2 H2O

Catalytic applications

Wilkinson's catalyst is best known for catalyzing the hydrogenation of olefins with molecular hydrogen. [11] [12] The mechanism of this reaction involves the initial dissociation of one or two triphenylphosphine ligands to give 14- or 12-electron complexes, respectively, followed by oxidative addition of H2 to the metal. Subsequent π-complexation of alkene, migratory insertion (intramolecular hydride transfer or olefin insertion), and reductive elimination complete the formation of the alkane product, e.g.: [13]

WilkinsonCycleJMBrown.png

In terms of their rates of hydrogenation, the degree of substitution on the olefin substrate is the key factor, since the rate-limiting step in the mechanism is the insertion into the olefin which is limited by the severe steric hindrance around the metal center. In practice, terminal and disubstituted alkenes are good substrates, but more hindered alkenes are slower to hydrogenate. The hydrogenation of alkynes is troublesome to control since alkynes tend to be reduced to alkanes, via intermediacy of the cis-alkene. [14] Ethylene reacts with Wilkinson's catalyst to give RhCl(C2H4)(PPh3)2, but it is not a substrate for hydrogenation. [10]

Wilkinson's catalyst also catalyzes many other hydrofunctionalization reactions including hydroacylation, hydroboration, and hydrosilylation of alkenes. [14] Hydroborations have been studied with catecholborane and pinacolborane. [15] It is also active for the hydrosilylation of alkenes. [16]

In the presence of strong base and hydrogen, Wilkinson's catalyst forms reactive Rh(I) species with superior catalytic activities on the hydrogenation of internal alkynes and functionalized tri-substituted alkenes. [17]

Reactions

RhCl(PPh3)3 reacts with carbon monoxide to give bis(triphenylphosphine)rhodium carbonyl chloride, trans-RhCl(CO)(PPh3)2. The same complex arises from the decarbonylation of aldehydes:

RhCl(PPh3)3 + RCHO → RhCl(CO)(PPh3)2 + RH + PPh3

Upon stirring in benzene solution, RhCl(PPh3)3 converts to the poorly soluble red-colored dimer [RhCl(PPh3)2]2. This conversion further demonstrates the lability of the triphenylphosphine ligands.

In the presence of base, H2, and additional triphenylphosphine, Wilkinson's complex converts to hydridotetrakis(triphenylphosphine)rhodium(I), HRh(PPh3)4. This 18e complex is also an active hydrogenation catalyst. [18]

See also

Related Research Articles

<span class="mw-page-title-main">Hydrogenation</span> Chemical reaction between molecular hydrogen and another compound or element

Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule, often an alkene. Catalysts are required for the reaction to be usable; non-catalytic hydrogenation takes place only at very high temperatures. Hydrogenation reduces double and triple bonds in hydrocarbons.

The Heck reaction is the chemical reaction of an unsaturated halide with an alkene in the presence of a base and a palladium catalyst to form a substituted alkene. It is named after Tsutomu Mizoroki and Richard F. Heck. Heck was awarded the 2010 Nobel Prize in Chemistry, which he shared with Ei-ichi Negishi and Akira Suzuki, for the discovery and development of this reaction. This reaction was the first example of a carbon-carbon bond-forming reaction that followed a Pd(0)/Pd(II) catalytic cycle, the same catalytic cycle that is seen in other Pd(0)-catalyzed cross-coupling reactions. The Heck reaction is a way to substitute alkenes.

<span class="mw-page-title-main">Rhodium(III) chloride</span> Chemical compound

Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)n, where n varies from 0 to 3. These are diamagnetic red-brown solids. The soluble trihydrated (n = 3) salt is the usual compound of commerce. It is widely used to prepare compounds used in homogeneous catalysis.

<span class="mw-page-title-main">Crabtree's catalyst</span> Chemical compound

Crabtree's catalyst is an organoiridium compound with the formula [C8H12IrP(C6H11)3C5H5N]PF6. It is a homogeneous catalyst for hydrogenation and hydrogen-transfer reactions, developed by Robert H. Crabtree. This air stable orange solid is commercially available and known for its directed hydrogenation to give trans stereoselectivity with respective of directing group.

Hydrosilylation, also called catalytic hydrosilation, describes the addition of Si-H bonds across unsaturated bonds. Ordinarily the reaction is conducted catalytically and usually the substrates are unsaturated organic compounds. Alkenes and alkynes give alkyl and vinyl silanes; aldehydes and ketones give silyl ethers. Hydrosilylation has been called the "most important application of platinum in homogeneous catalysis."

<span class="mw-page-title-main">Hydroamination</span> Addition of an N–H group across a C=C or C≡C bond

In organic chemistry, hydroamination is the addition of an N−H bond of an amine across a carbon-carbon multiple bond of an alkene, alkyne, diene, or allene. In the ideal case, hydroamination is atom economical and green. Amines are common in fine-chemical, pharmaceutical, and agricultural industries. Hydroamination can be used intramolecularly to create heterocycles or intermolecularly with a separate amine and unsaturated compound. The development of catalysts for hydroamination remains an active area, especially for alkenes. Although practical hydroamination reactions can be effected for dienes and electrophilic alkenes, the term hydroamination often implies reactions metal-catalyzed processes.

Martin Arthur Bennett FRS is an Australian inorganic chemist. He gained recognition for studies on the co-ordination chemistry of tertiary phosphines, olefins, and acetylenes, and the relationship of their behaviour to homogeneous catalysis.

In organometallic chemistry, a migratory insertion is a type of reaction wherein two ligands on a metal complex combine. It is a subset of reactions that very closely resembles the insertion reactions, and both are differentiated by the mechanism that leads to the resulting stereochemistry of the products. However, often the two are used interchangeably because the mechanism is sometimes unknown. Therefore, migratory insertion reactions or insertion reactions, for short, are defined not by the mechanism but by the overall regiochemistry wherein one chemical entity interposes itself into an existing bond of typically a second chemical entity e.g.:

<span class="mw-page-title-main">Organoiridium chemistry</span> Chemistry of organometallic compounds containing an iridium-carbon bond

Organoiridium chemistry is the chemistry of organometallic compounds containing an iridium-carbon chemical bond. Organoiridium compounds are relevant to many important processes including olefin hydrogenation and the industrial synthesis of acetic acid. They are also of great academic interest because of the diversity of the reactions and their relevance to the synthesis of fine chemicals.

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<span class="mw-page-title-main">Organorhodium chemistry</span> Field of study

Organorhodium chemistry is the chemistry of organometallic compounds containing a rhodium-carbon chemical bond, and the study of rhodium and rhodium compounds as catalysts in organic reactions.

<span class="mw-page-title-main">Dichlorotris(triphenylphosphine)ruthenium(II)</span> Chemical compound

Dichlorotris(triphenylphosphine)ruthenium(II) is a coordination complex of ruthenium. It is a chocolate brown solid that is soluble in organic solvents such as benzene. The compound is used as a precursor to other complexes including those used in homogeneous catalysis.

In chemistry, metal-catalysed hydroboration is a reaction used in organic synthesis. It is one of several examples of homogeneous catalysis.

<span class="mw-page-title-main">Metal-phosphine complex</span>

A metal-phosphine complex is a coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R3P (R = alkyl, aryl). Metal phosphine complexes are useful in homogeneous catalysis. Prominent examples of metal phosphine complexes include Wilkinson's catalyst (Rh(PPh3)3Cl), Grubbs' catalyst, and tetrakis(triphenylphosphine)palladium(0).

Dehydrogenation of amine-boranes or dehydrocoupling of amine-boranes is a chemical process in main group and organometallic chemistry wherein dihydrogen is released by the coupling of two or more amine-borane adducts. This process is of due to the potential of using amine-boranes for hydrogen storage.

<span class="mw-page-title-main">Tris(triphenylphosphine)rhodium carbonyl hydride</span> Chemical compound

Carbonyl hydrido tris(triphenylphosphine)rhodium(I) [Carbonyl(hydrido)tris(triphenylphosphane)rhodium(I)] is an organorhodium compound with the formula [RhH(CO)(PPh3)3] (Ph = C6H5). It is a yellow, benzene-soluble solid, which is used industrially for hydroformylation.

In organometallic chemistry, a transition metal alkyne complex is a coordination compound containing one or more alkyne ligands. Such compounds are intermediates in many catalytic reactions that convert alkynes to other organic products, e.g. hydrogenation and trimerization.

The Tsuji–Wilkinson decarbonylation reaction is a method for the decarbonylation of aldehydes and some acyl chlorides. The reaction name recognizes Jirō Tsuji, whose team first reported the use of Wilkinson's catalyst (RhCl(PPh3)3) for these reactions:

Clark Landis is an American chemist, whose research focuses on organic and inorganic chemistry. He is currently a Professor of Chemistry at the University of Wisconsin–Madison. He was awarded the ACS Award in Organometallic Chemistry in 2010, and is a fellow of the American Chemical Society and the American Association for the Advancement of Science.

<span class="mw-page-title-main">Bis(triphenylphosphine)rhodium carbonyl chloride</span> Chemical compound

Bis(triphenylphosphine)rhodium carbonyl chloride is the organorhodium complex with the formula [RhCl(CO)(PPh3)2]. This complex of rhodium(I) is a bright yellow, air-stable solid. It is the Rh analogue of Vaska's complex, the corresponding iridium complex. With regards to its structure, the complex is square planar with mutually trans triphenylphosphine (PPh3) ligands. The complex is a versatile homogeneous catalyst.

References

  1. 1 2 Osborn, J. A.; Wilkinson, G. (1967). "Tris(triphenylphosphine)halorhodium(I)". Inorganic Syntheses. Vol. 10. p. 67. doi:10.1002/9780470132418.ch12. ISBN   9780470132418.
  2. ↑ "Chlorotris(triphenylphosphine)rhodium(I)". pubchem.ncbi.nlm.nih.gov.
  3. ↑ Meakin, P.; Jesson, J. P.; Tolman, C. A. (1 May 1972). "Nature of chlorotris(triphenylphosphene)rhodium in solution and its reaction with hydrogen". Journal of the American Chemical Society. 94 (9): 3240–3242. doi:10.1021/ja00764a061. ISSN   0002-7863.
  4. ↑ Duckett, Simon B.; Newell, Connie L.; Eisenberg, Richard (1994). "Observation of New Intermediates in Hydrogenation Catalyzed by Wilkinson's Catalyst, RhCl(PPh3)3, Using Parahydrogen-Induced Polarization". Journal of the American Chemical Society. 116 (23): 10548–10556. doi:10.1021/ja00102a023.
  5. ↑ Halpern, Jack (1 January 1981). "Mechanistic aspects of homogeneous catalytic hydrogenation and related processes". Inorganica Chimica Acta. 50: 11–19. doi:10.1016/S0020-1693(00)83716-0.
  6. ↑ Hartwig, John F. (2010). Organotransition metal chemistry- From bonding to Catalysis. University Science Books. ISBN   978-1-891389-53-5.
  7. ↑ Bennett, Michael J.; Donaldson, Peter B. (1977). "Crystal and molecular structure of the orange and red allotropes of chlorotris(triphenylphosphine)rhodium(I)". Inorganic Chemistry. 16 (3): 655–660. doi:10.1021/ic50169a033.
  8. ↑ Bennett, M. A.; Milner, D. L. (1969). "Chlorotris(triphenylphosphine)iridium(I) and Related Complexes. Oxidative Addition Reactions and Hydrogen Abstraction from the Coordinated Ligand". Journal of the American Chemical Society. 91 (25): 6983–6994. doi:10.1021/ja01053a016.
  9. ↑ Bennett, M. A.; Longstaff, P. A. (1965). "Complexes of Rhodium(I) with Triphenylphosphine". Chem. Ind. (London). 1965: 846.
  10. 1 2 Osborn, J. A.; Jardine, F. H.; Young, J. F.; Geoffrey Wilkinson (1966). "The Preparation and Properties of Tris(triphenylphosphine)halogenorhodium(I) and Some Reactions Thereof Including Catalytic Homogeneous Hydrogenation of Olefins and Acetylenes and Their Derivatives". Journal of the Chemical Society A . 1966: 1711–1732. doi:10.1039/J19660001711.
  11. ↑ Arthur Birch; Williamson, D. H. (1976). "Homogeneous Hydrogenation Catalysts in Organic Synthesis". Organic Reactions . 24: 1.
  12. ↑ James, B. R. (1973). Homogeneous Hydrogenation. New York, NY: John Wiley & Sons.
  13. ↑ Rzepa, Henry (21 January 2024). "A mechanistic exploration of the Wilkinson hydrogenation catalyst. Part 1: Model templates". Chemistry with a Twist.
  14. 1 2 Kevin Burgess, Wilfred van der Donk, Chul-Ho Jun, Young Jun Park, "Chlorotris(triphenylphosphine)-rhodium(I)" Encyclopedia of Reagents for Organic Synthesis 2005 John Wiley & Sons. doi : 10.1002/047084289X.rc162s.pub2
  15. ↑ Evans, D. A.; Fu, G. C.; Hoveyda, A. H. (1988). "Rhodium(I)-catalyzed hydroboration of olefins. The documentation of regio- and stereochemical control in cyclic and acyclic systems". J. Am. Chem. Soc. 110 (20): 6917–6918. doi:10.1021/ja00228a068.
  16. ↑ Ojima, I.; Kogure, T. (1972). "Selective reduction of α,β-unsaturated terpene carbonyl compounds using hydrosilane-rhodium(I) complex combinations". Tetrahedron Lett. 13 (49): 5035–5038. doi:10.1016/S0040-4039(01)85162-5.
  17. ↑ Perea Buceta, Jesus E.; Fernández, Israel; Heikkinen, Sami; Axenov, Kirill; King, Alistair W. T.; Niemi, Teemu; Nieger, Martin; Leskelä, Markku; Repo, Timo (23 November 2015) [2015]. "Diverting Hydrogenations with Wilkinson's Catalyst towards Highly Reactive Rhodium(I) Species". Angewandte Chemie International Edition. 54 (48): 14321–14325. doi:10.1002/anie.201506216. ISSN   1521-3773. PMID   26437764.
  18. ↑ Eduardo Peña-Cabrera "Hydridotetrakis(triphenylphosphine)rhodium" Encyclopedia of Reagents for Organic Synthesis, 2001, John Wiley & Sons. doi : 10.1002/047084289X.rh030m
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