Martin A. Bennett

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Martin A. Bennett
FRS
EducationImperial College
EmployerAustralian National University

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.

Contents

Professional career

Born in London, Bennett studied at The Haberdashers' Aske's Boys' School and received his PhD under the supervision of Geoffrey Wilkinson at Imperial College. He was subsequently a researcher at University College, London with Ronald Nyholm and then with Arthur Adamson. While in London, he prepared the rhodium complex [RhCl(PPh3)3], now known as Wilkinson's catalyst. [1] In the 1960s he took a position in the Research School of Chemistry at the Australian National University in Canberra.

Contributions

At ANU, Bennett developed several lines of research broadly on themes in organometallic chemistry. This included extending work on the iridium analogue of Wilkinson's catalyst which he began at University College with Milner. [2] Wilkinson's catalyst can be prepared by reducing rhodium(III) chloride in boiling ethanol in the presence of an excess of triphenylphosphine, [3] [4] but the equivalent preparative conditions lead not to [IrCl(PPh3)3] but instead to a mixture of iridium(III) products, primarily the hydrogen chloride adduct of the analogue: [2]

IrCl3(H2O)3  +   4 PPh3   [HIrCl2(PPh3)3]   +   OPPh3   +   HCl   +   2 H2O

Bennett prepared the analogue from the 1,5-cyclooctadiene (1,5-cod) iridium(I) dimer, [(η4-1,5-cod)Ir(μ-Cl)]2, using an excess of triphenylphosphine in ligroin under reflux. The product is isomorphous with Wilkinson's catalyst but does not lose a triphenylphosphine ligand through dissociation in organic solvents anywhere near as readily. [2] A phosphine is lost under oxidative conditions with chlorine, affording initially [IrCl3(PPh3)2] and with excess chlorine, the iridium(IV) complex [IrCl4(PPh3)2] is obtained. [IrCl(PPh3)3] rearranges on heating via an insertion reaction, an ortho-metalation of one of the phenyl moieties, to produce the six-co-ordinate organometallic iridium(III) hydride [HIrCl(PPh3)2(Ph2PC6H4)] [5] an example of iridium(I)-iridium(III) tautomerism involving the formation of a bidentate phosphine ligand with a carbon donor atom: [2] [5]

[(η4-1,5-cod)Ir(μ-Cl)]2  +   4 PPh3   2 [IrCl(PPh3)3]   +   2 1,5-cod
The (cymene)ruthenium dichloride dimer RuCymCl2.png
The (cymene)ruthenium dichloride dimer

Bennett was the first to prepare complexes of cyclooctyne, cycloheptyne, and cyclohexyne. He developed rare examples of metal-alkene complexes that exist in two oxidation states. His group first prepared the now-popular reagent (cymene)ruthenium dichloride dimer, [6] which is converted into a monomer by reaction with 1,1'-bis(diphenylphosphino)ferrocene for use in borrowing hydrogen catalysis [7]

Related Research Articles

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

Wilkinson's catalyst (chlorido­tris(triphenylphosphene)­rhodium(I)) is a coordination complex of rhodium with the formula [RhCl(PPh3)3], 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.

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

Vaska's complex is the trivial name for the chemical compound trans-carbonylchlorobis(triphenylphosphine)iridium(I), which has the formula IrCl(CO)[P(C6H5)3]2. This square planar diamagnetic organometallic complex consists of a central iridium atom bound to two mutually trans triphenylphosphine ligands, carbon monoxide and a chloride ion. The complex was first reported by J. W. DiLuzio and Lauri Vaska in 1961. Vaska's complex can undergo oxidative addition and is notable for its ability to bind to O2 reversibly. It is a bright yellow crystalline solid.

<span class="mw-page-title-main">Triphenylphosphine</span> Chemical compound

Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to PPh3 or Ph3P. It is versatile compound that is widely used as a reagent in organic synthesis and as a ligand for transition metal complexes, including ones that serve as catalysts in organometallic chemistry. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene and diethyl ether.

<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 solids featuring octahedral Rh(III) centres. Depending on the value of n, the material is either a dense brown solid or a soluble reddish salt. The soluble trihydrated (n = 3) salt is widely used to prepare compounds used in homogeneous catalysis, notably for the industrial production of acetic acid and hydroformylation.

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

Iridium(III) chloride is the inorganic compound with the formula IrCl3. The anhydrous compound is relatively rare, but the related hydrate is much more commonly encountered. The anhydrous salt has two polymorphs, α and β, which are brown and red colored respectively. More commonly encountered is the hygroscopic dark green trihydrate IrCl3(H2O)3 which is a common starting point for iridium chemistry.

<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.

<span class="mw-page-title-main">Cyclooctadiene rhodium chloride dimer</span> Chemical compound

Cyclooctadiene rhodium chloride dimer is the organorhodium compound with the formula Rh2Cl2(C8H12)2, commonly abbreviated [RhCl(COD)]2 or Rh2Cl2(COD)2. This yellow-orange, air-stable compound is a widely used precursor to homogeneous catalysts.

<span class="mw-page-title-main">Metallacycle</span>

In organometallic chemistry, a metallacycle is a derivative of a carbocyclic compound wherein a metal has replaced at least one carbon center; this is to some extent similar to heterocycles. Metallacycles appear frequently as reactive intermediates in catalysis, e.g. olefin metathesis and alkyne trimerization. In organic synthesis, directed ortho metalation is widely used for the functionalization of arene rings via C-H activation. One main effect that metallic atom substitution on a cyclic carbon compound is distorting the geometry due to the large size of typical metals.

<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.

<span class="mw-page-title-main">Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium</span> Chemical compound

Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium is the organoruthenium half-sandwich compound with formula RuCl(PPh3)2(C5H5). It as an air-stable orange crystalline solid that is used in a variety of organometallic synthetic and catalytic transformations. The compound has idealized Cs symmetry. It is soluble in chloroform, dichloromethane, and acetone.

<span class="mw-page-title-main">Dimethylphenylphosphine</span> Chemical compound

Dimethylphenylphosphine is an organophosphorus compound with a formula P(C6H5)(CH3)2. The phosphorus is connected to a phenyl group and two methyl groups, making it the simplest aromatic alkylphosphine. It is colorless air sensitive liquid. It is a member of series (CH3)3-n(C6H5)2P that also includes n = 0, n = 2, and n = 3 that are often employed as ligands in metal phosphine complexes.

Organoplatinum chemistry is the chemistry of organometallic compounds containing a carbon to platinum chemical bond, and the study of platinum as a catalyst in organic reactions. Organoplatinum compounds exist in oxidation state 0 to IV, with oxidation state II most abundant. The general order in bond strength is Pt-C (sp) > Pt-O > Pt-N > Pt-C (sp3). Organoplatinum and organopalladium chemistry are similar, but organoplatinum compounds are more stable and therefore less useful as catalysts.

<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.

<span class="mw-page-title-main">Hydrogenation of carbon–nitrogen double bonds</span>

In chemistry, the hydrogenation of carbon–nitrogen double bonds is the addition of the elements of dihydrogen (H2) across a carbon–nitrogen double bond, forming amines or amine derivatives. Although a variety of general methods have been developed for the enantioselective hydrogenation of ketones, methods for the hydrogenation of carbon–nitrogen double bonds are less general. Hydrogenation of imines is complicated by both syn/anti isomerization and tautomerization to enamines, which may be hydrogenated with low enantioselectivity in the presence of a chiral catalyst. Additionally, the substituent attached to nitrogen affects both the reactivity and spatial properties of the imine, complicating the development of a general catalyst system for imine hydrogenation. Despite these challenges, methods have been developed that address particular substrate classes, such as N-aryl, N-alkyl, and endocyclic imines.

<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).

<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.

<span class="mw-page-title-main">Chlorobis(cyclooctene)iridium dimer</span> Chemical compound

Chlorobis(cyclooctene)iridium dimer is an organoiridium compound with the formula Ir2Cl2(C8H14)4, where C8H14 is cis-cyclooctene. Sometimes abbreviated Ir2Cl2(coe)4, it is a yellow, air-sensitive solid that is used as a precursor to many other organoiridium compounds and catalysts.

<span class="mw-page-title-main">Hydridotetrakis(triphenylphosphine)rhodium(I)</span> Chemical compound

Hydridotetrakis(triphenylphosphine)rhodium(I) is the coordination complex with the formula HRh[P(C6H5)3]4. It consists of a Rh(I) center complexed to four triphenylphosphine (PPh3) ligands and one hydride. The molecule has idealized C3v symmetry. The compound is a homogeneous catalyst for hydrogenation and related reactions. It is a yellow solid that dissolves in aromatic solvents.

<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. Bennett, M. A.; Longstaff, P. A. (1965). "Complexes of Rhodium(I) with Triphenylphosphine". Chem. Ind. : 846.
  2. 1 2 3 4 Bennett, M. A.; Milner, D. L. (1967). "Chlorotris(triphenylphosphine)iridium(I): An example of hydrogen transfer to a metal from a co-ordinated ligand". Chem. Commun. (12): 581–582. doi:10.1039/C19670000581.
  3. Osborn, J. A.; Jardine, F. H.; Young, J. F.; Wilkinson, G. (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". J. Chem. Soc. A . 1966: 1711–1732. doi:10.1039/J19660001711.
  4. Osborn, J. A.; Wilkinson, G. (1967). "Tris(triphenylphosphine)halorhodium(I)". Inorganic Syntheses. Vol. 10. pp. 67–71. doi:10.1002/9780470132418.ch12. ISBN   9780470132418.{{cite book}}: |journal= ignored (help)
  5. 1 2 Bennett, M. A.; Milner, D. L. (1969). "Chlorotris(triphenylphosphine)iridium(I) and related complexes. Oxidative addition reactions and hydrogen abstraction from the coordinated ligand". J. Am. Chem. Soc. 91 (25): 6983–6994. doi:10.1021/ja01053a016.
  6. Bennett, M. A.; Huang, T.-N.; Matheson, T. W.; Smith, A. K. (2007). "16. (η 6 -Hexamethylbenzene)Ruthenium Complexes". Inorganic Syntheses. Vol. 21. pp. 74–78. doi:10.1002/9780470132524.ch16. ISBN   9780470132524.{{cite book}}: |journal= ignored (help)
  7. Hamid, Malai Haniti S.A.; Slatford, Paul A.; Williams, Jonathan M.J. (2007). "Borrowing Hydrogen in the Activation of Alcohols". Adv. Synth. Catal. 349 (10): 1555–1575. doi:10.1002/adsc.200600638.