olefin metathesis

The reaction requires metal catalysts. Most commercially important processes employ heterogeneous catalysts. The heterogeneous catalysts are often prepared by in-situ activation of a metal halide (MCl_x) using organoaluminium or organotin compounds, e.g. combining MCl_x–EtAlCl₂. A typical catalyst support is alumina. Commercial catalysts are often based on molybdenum and ruthenium. Well-defined organometallic compounds have mainly been investigated for small-scale reactions or in academic research. The homogeneous catalysts are often classified as Schrock catalysts and Grubbs catalysts. Schrock catalysts feature molybdenum(VI)- and tungsten(VI)-based centers supported by alkoxide and imido ligands.{{cite journal | author = R.R. Schrock | title = High-oxidation-state molybdenum and tungsten alkylidene complexes | year = 1986 | journal = Accounts of Chemical Research| doi = 10.1021/ar00131a003 | volume = 19 | issue = 11 | pages = 342–348}}

File:SchrockMetathesisCatalysts.png

Grubbs catalysts, on the other hand, are ruthenium(II) carbenoid complexes.{{cite journal | author1 = Ileana Dragutan | author2 = Valerian Dragutan | author3 = Petru Filip | title = Recent developments in design and synthesis of well-defined ruthenium metathesis catalysts – a highly successful opening for intricate organic synthesis | year = 2005 | url = http://arkat-usa.org/ark/journal/2005/I10_Balaban/1334/1334.asp | pages = 105–129 | journal = Arkivoc | access-date = 6 October 2005 | archive-url = https://web.archive.org/web/20060512173852/http://arkat-usa.org/ark/journal/2005/I10_Balaban/1334/1334.asp | archive-date = 12 May 2006 }} Many variations of Grubbs catalysts are known. Some have been modified with a chelating isopropoxybenzylidene ligand to form the related Hoveyda–Grubbs catalyst.

File:GrubbsMetathesisCatalysts.png

Olefin metathesis has several industrial applications. Almost all commercial applications employ heterogeneous catalysts using catalysts developed well before the Nobel-Prize winning work on homogeneous complexes.{{cite journal|last1=Ghashghaee|first1=Mohammad|title=Heterogeneous catalysts for gas-phase conversion of ethylene to higher olefins|journal=Reviews in Chemical Engineering|volume=34|issue=5|pages=595–655|doi=10.1515/revce-2017-0003|year=2018|s2cid=103664623 }} Representative processes include:

• The Phillips Triolefin and the Olefin conversion technology. This process interconverts propylene with ethylene and 2-butenes. Rhenium and molybdenum catalysts are used. Nowadays, only the reverse reaction, i.e., the conversion of ethylene and 2-butene to propylene is industrially practiced, however.
• Shell higher olefin process (SHOP) produces (alpha-olefins) for conversion to detergents. The process recycles certain olefin fractions using metathesis.{{cite book|title=Industrial Organic Chemistry|author=Klaus Weissermel, Hans-Jurgen Arpe|publisher=John Wiley & Sons|edition=3rd|year=1997|isbn=3-527-28838-4}}
• Neohexene production, which involves ethenolysis of isobutene dimers. The catalyst is derived from tungsten trioxide supported on silica and MgO.
• 1,5-Hexadiene and 1,9-decadiene, useful crosslinking agents and synthetic intermediates, are produced commercially by ethenolysis of 1,5-cyclooctadiene and cyclooctene. The catalyst is derived from Re₂O₇ on alumina.

Molecular catalysts have been explored for the preparation of a variety of potential applications,{{cite journal|last=Kotha|first=S|author2=Waghule GT|title=Diversity Oriented Approach to Crownophanes by Enyne Metathesis and Diels–Alder Reaction as Key Steps|journal=The Journal of Organic Chemistry|date=June 2012|volume=77|issue=14|pages=6314–6318|doi=10.1021/jo300766f|pmid=22731677}} such as the synthesis of pharmaceutical drugs,{{cite journal |vauthors=McCauley JA, McIntyre CJ, Rudd MT, Nguyen KT, Romano JJ, Butcher JW, Gilbert KF, Bush KJ, Holloway MK, Swestock J, Wan BL, Carroll SS, DiMuzio JM, Graham DJ, Ludmerer SW, Mao SS, Stahlhut MW, Fandozzi CM, Trainor N, Olsen DB, Vacca JP, Liverton NJ | title = Discovery of vaniprevir (MK-7009), a macrocyclic hepatitis C virus NS3/4a protease inhibitor | journal = Journal of Medicinal Chemistry| volume = 53 | issue = 6 | pages = 2443–63 |date=March 2010 | pmid = 20163176 | doi = 10.1021/jm9015526 }} the manufacturing of high-strength materials, the preparation of cancer-targeting nanoparticles,{{cite journal |vauthors=Matson JB, Grubbs RH | title = Synthesis of Fluorine-18 Functionalized Nanoparticles for use as in vivo Molecular Imaging Agents | journal = Journal of the American Chemical Society| volume = 130 | issue = 21 | year = 2008 | pages = 6731–6733 | doi = 10.1021/ja802010d | pmid = 18452296 | bibcode = 2008JAChS.130.6731M | url = https://authors.library.caltech.edu/77503/2/ja802010d-file002.pdf }} and the conversion of renewable plant-based feedstocks into hair and skin care products.{{cite press release | title = Dow Corning and Elevance Announce Partnership to Market Naturally Derived Ingredients in Personal Care Applications | publisher = Elevance Renewable Sciences | date = 9 September 2008 | url = http://www.elevance.com/media/news-releases/dow-corning-and-elevance-announce-partnership-to-market-naturally-derived-ingredients-in-personal-care-applications/ | access-date = 19 January 2012 | archive-date = 9 December 2011 | archive-url = https://web.archive.org/web/20111209204012/http://www.elevance.com/media/news-releases/dow-corning-and-elevance-announce-partnership-to-market-naturally-derived-ingredients-in-personal-care-applications/ | url-status = dead }}

Some classes of olefin metathesis include:

• Cross metathesis (CM)
• Ring-opening metathesis (ROM)
• Ring-closing metathesis (RCM)
• Ring-opening metathesis polymerization (ROMP)
• Acyclic diene metathesis (ADMET)
• Ethenolysis

Hérisson and Chauvin first proposed the widely accepted mechanism of transition metal alkene metathesis.{{cite journal | last1 = Jean-Louis Hérisson | first1 = Par | last2 = Chauvin | first2 = Yves | journal = Die Makromolekulare Chemie| title=Catalyse de transformation des oléfines par les complexes du tungstène. II. Télomérisation des oléfines cycliques en présence d'oléfines acycliques | language=fr | volume = 141| issue=1 | pages = 161–176 | year = 1971 | doi = 10.1002/macp.1971.021410112 }} The direct [2+2] cycloaddition of two alkenes is formally symmetry forbidden and thus has a high activation energy. The Chauvin mechanism involves the [2+2] cycloaddition of an alkene double bond to a transition metal alkylidene to form a metallacyclobutane intermediate. The metallacyclobutane produced can then cycloeliminate to give either the original species or a new alkene and alkylidene. Interaction with the d-orbitals on the metal catalyst lowers the activation energy enough that the reaction can proceed rapidly at modest temperatures.

Image:Metathesis mechanism jypx3.png

Olefin metathesis involves little change in enthalpy for unstrained alkenes. Product distributions are determined instead by le Chatelier's Principle, i.e. entropy.

File:Wikipedia-OlefinMetathesisCategories.png

Cross metathesis and ring-closing metathesis are driven by the entropically favored evolution of ethylene or propylene, which can be removed from the system because they are gases. Because of this CM and RCM reactions often use alpha-olefins. The reverse reaction of CM of two alpha-olefins, ethenolysis, can be favored but requires high pressures of ethylene to increase ethylene concentration in solution. The reverse reaction of RCM, ring-opening metathesis, can likewise be favored by a large excess of an alpha-olefin, often styrene. Ring-opening metathesis usually involves a strained alkene (often a norbornene) and the release of ring strain drives the reaction. Ring-closing metathesis, conversely, usually involves the formation of a five- or six-membered ring, which is enthalpically favorable; although these reactions tend to also evolve ethylene, as previously discussed. RCM has been used to close larger macrocycles, in which case the reaction may be kinetically controlled by running the reaction at high dilutions.{{cite journal | doi = 10.1002/ejoc.200700744 |author1=Sambasivarao Kotha |author2=Kuldeep Singh | title = Cross-enyne and ring-closing metathesis cascade: A building-block approach suitable for diversity-oriented synthesis of densely functionalized macroheterocycles with amino acid scaffolds| year = 2007 | pages = 5909–5916 | issue = 35 | volume = 2007 | journal = European Journal of Organic Chemistry}} The same substrates that undergo RCM can undergo acyclic diene metathesis, with ADMET favored at high concentrations. The Thorpe–Ingold effect may also be exploited to improve both reaction rates and product selectivity.

Cross-metathesis is synthetically equivalent to (and has replaced) a procedure of ozonolysis of an alkene to two ketone fragments followed by the reaction of one of them with a Wittig reagent.

"Olefin metathesis is a child of industry and, as with many catalytic processes, it was discovered by accident."{{cite encyclopedia|encyclopedia=Kirk-Othmer Encyclopedia of Chemical Technology|author=Lionel Delaude |author2=Alfred F. Noels |year=2005| doi=10.1002/0471238961.metanoel.a01|place=Weinheim|publisher=Wiley-VCH|isbn = 978-0-471-23896-6|chapter = Metathesis}}

As part of ongoing work in what would later become known as Ziegler–Natta catalysis Karl Ziegler discovered the conversion of ethylene into 1-butene instead of a saturated long-chain hydrocarbon (see nickel effect).{{cite journal | last1 = Ziegler | first1 = Karl | last2 = Holzkamp | first2 = E. | last3 = Breil | first3 = H. | last4 = Martin | first4 = H. | title = Polymerisation von Äthylen und anderen Olefinen | journal = Angewandte Chemie| volume = 67 | issue=16 | page = 426 | year = 1955 | doi = 10.1002/ange.19550671610| bibcode = 1955AngCh..67..426Z }}

In 1960 a Du Pont research group polymerized norbornene to polynorbornene using lithium aluminum tetraheptyl and titanium tetrachloride{{cite journal | last1 = Truett | first1 = W. L. | last2 = Johnson | first2 = D. R. | last3 = Robinson | first3 = I. M. | last4 = Montague | first4 = B. A. |title= Polynorbornene by Coördination Polymerization| journal = Journal of the American Chemical Society| volume = 82 |issue=9 | pages = 2337–2340 | year = 1960 | doi = 10.1021/ja01494a057| bibcode = 1960JAChS..82.2337T }} (a patent by this company on this topic dates back to 1955A. W. Anderson and N. G. Merckling, U. S. {{US Patent|2721189}}

(18 October 1955)),

:Image:MetathesisDupont.svg

a reaction then classified as a so-called coordination polymerization. According to the then proposed reaction mechanism a RTiX titanium intermediate first coordinates to the double bond in a pi complex. The second step then is a concerted SNi reaction breaking a CC bond and forming a new alkylidene-titanium bond; the process then repeats itself with a second monomer:

:Image:MetathesisDuPontMechanism.svg

Only much later the polynorbornene was going to be produced through ring opening metathesis polymerisation. The DuPont work was led by Herbert S. Eleuterio. Giulio Natta in 1964 also observed the formation of an unsaturated polymer when polymerizing cyclopentene with tungsten and molybdenum halides.{{cite journal | last1 = Natta | first1 = G. | last2 = Dall'asta | first2 = G. | last3 = Mazzanti | first3 = G. | title = Stereospecific Homopolymerization of Cyclopentene | journal = Angewandte Chemie International Edition in English| volume = 3 | issue=11 | pages = 723–729 | year = 1964 | doi = 10.1002/anie.196407231}}

In a third development leading up to olefin metathesis, researchers at Phillips Petroleum Company in 1964{{cite journal | last1 = Banks | first1 = R. L. | last2 = Bailey | first2 = G. C. | title = Olefin Disproportionation. A New Catalytic Process | journal = Industrial & Engineering Chemistry Product Research and Development| volume = 3 |issue=3| pages = 170–173 | year = 1964 | doi = 10.1021/i360011a002}} described olefin disproportionation with catalysts molybdenum hexacarbonyl, tungsten hexacarbonyl, and molybdenum oxide supported on alumina for example converting propylene to an equal mixture of ethylene and 2-butene for which they proposed a reaction mechanism involving a cyclobutane (they called it a quasicyclobutane) – metal complex:

:Image:MetathesisCyclobutaneMech.svg

This particular mechanism is symmetry forbidden based on the Woodward–Hoffmann rules first formulated two years earlier. Cyclobutanes have also never been identified in metathesis reactions, which is another reason why it was quickly abandoned.

Then in 1967 researchers led by Nissim Calderon at the Goodyear Tire and Rubber Company described a novel catalyst system for the metathesis of 2-pentene based on tungsten hexachloride, ethanol, and the organoaluminum compound EtAlMe₂. The researchers proposed a name for this reaction type: olefin metathesis.{{cite journal | last1 = Calderon | first1 = N | title = Olefin metathesis – A novel reaction for skeletal transformations of unsaturated hydrocarbons | journal = Tetrahedron Letters| volume = 8 |issue = 34 | pages = 3327–3329 | year = 1967 | doi = 10.1016/S0040-4039(01)89881-6 | last2 = Chen | first2 = Hung Yu | last3 = Scott | first3 = Kenneth W.}} Formerly the reaction had been called "olefin disproportionation."

:Image:MetathesisCalderon1967.svg

In this reaction 2-pentene forms a rapid (a matter of seconds) chemical equilibrium with 2-butene and 3-hexene. No double bond migrations are observed; the reaction can be started with the butene and hexene as well and the reaction can be stopped by addition of methanol.

The Goodyear group demonstrated that the reaction of regular 2-butene with its all-deuterated isotopologue yielded C₄H₄D₄ with deuterium evenly distributed.{{cite journal | last1 = Calderon | first1 = Nissim. | last2 = Ofstead | first2 = Eilert A. | last3 = Ward | first3 = John P. | last4 = Judy | first4 = W. Allen. | last5 = Scott | first5 = Kenneth W. | title = Olefin metathesis. I. Acyclic vinylenic hydrocarbons | journal = Journal of the American Chemical Society| volume = 90 | issue=15 | pages = 4133–4140 | year = 1968 | doi = 10.1021/ja01017a039| bibcode = 1968JAChS..90.4133C }} In this way they were able to differentiate between a transalkylidenation mechanism and a transalkylation mechanism (ruled out):

:Image:MetathesisCalderon1976Mechanism.svg

In 1971 Chauvin proposed a four-membered metallacycle intermediate to explain the statistical distribution of products found in certain metathesis reactions.{{cite journal | last1 = Jean-Louis Hérisson | first1 = Par | last2 = Chauvin | first2 = Yves | title=Catalyse de transformation des oléfines par les complexes du tungstène. II. Télomérisation des oléfines cycliques en présence d'oléfines acycliques | journal = Die Makromolekulare Chemie| volume = 141 | issue=1 | pages = 161–176 | year = 1971 | doi = 10.1002/macp.1971.021410112}} This mechanism is today considered the actual mechanism taking place in olefin metathesis.

:Image:MetathesisMetallacyclemechanism.svg

Chauvin's experimental evidence was based on the reaction of cyclopentene and 2-pentene with the homogeneous catalyst tungsten(VI) oxytetrachloride and tetrabutyltin:

:Image:MetathesisChauvin1971.svg

The three principal products C9, C10 and C11 are found in a 1:2:1 regardless of conversion. The same ratio is found with the higher oligomers. Chauvin also explained how the carbene forms in the first place: by alpha-hydride elimination from a carbon metal single bond. For example, propylene (C3) forms in a reaction of 2-butene (C4) with tungsten hexachloride and tetramethyltin (C1).

In the same year Pettit who synthesised cyclobutadiene a few years earlier independently came up with a competing mechanism.{{cite journal | last1 = S. Lewandos | first1 = G | title = A proposed mechanism for the metal-catalysed disproportionation reaction of olefins | journal = Tetrahedron Letters| volume = 12 | issue=11 | pages = 789–793 | year = 1971 | doi = 10.1016/S0040-4039(01)96558-X | last2 = Pettit | first2 = R.}} It consisted of a tetramethylene intermediate with sp³ hybridized carbon atoms linked to a central metal atom with multiple three-center two-electron bonds.

:Image:MetathesisPettitmechanism.svg

Experimental support offered by Pettit for this mechanism was based on an observed reaction inhibition by carbon monoxide in certain metathesis reactions of 4-nonene with a tungsten metal carbonyl{{cite journal | last1 = Lewandos | first1 = Glenn S. | last2 = Pettit | first2 = R. | title = Mechanism of the metal-catalyzed disproportionation of olefins | journal = Journal of the American Chemical Society| volume = 93 | issue=25 | pages = 7087–7088 | year = 1971 | doi = 10.1021/ja00754a067| bibcode = 1971JAChS..93.7087L }}

Robert H. Grubbs got involved in metathesis in 1972 and also proposed a metallacycle intermediate but one with four carbon atoms in the ring.{{cite journal | last1 = Grubbs | first1 = Robert H. | last2 = Brunck | first2 = Terence K. | title = Possible intermediate in the tungsten-catalyzed olefin metathesis reaction | journal = Journal of the American Chemical Society| volume = 94 | issue=7 | pages = 2538–2540 | year = 1972 | doi = 10.1021/ja00762a073| bibcode = 1972JAChS..94.2538G }} The group he worked in reacted 1,4-dilithiobutane with tungsten hexachloride in an attempt to directly produce a cyclomethylenemetallacycle producing an intermediate, which yielded products identical with those produced by the intermediate in the olefin metathesis reaction. This mechanism is pairwise:

:Image:MetathesisGrubbs1972tetramethylenemetallocycle.svg

In 1973 Grubbs found further evidence for this mechanism by isolating one such metallacycle not with tungsten but with platinum by reaction of the dilithiobutane with cis-bis(triphenylphosphine)dichloroplatinum(II){{cite journal | last1 = Biefeld | first1 = Carol G. | last2 = Eick | first2 = Harry A. | last3 = Grubbs | first3 = Robert H. | title = Crystal structure of bis(triphenylphosphine)tetramethyleneplatinum(II) | journal = Inorganic Chemistry| volume = 12 | issue=9 | pages = 2166–2170 | year = 1973 | doi = 10.1021/ic50127a046}}

In 1975 Katz also arrived at a metallacyclobutane intermediate consistent with the one proposed by Chauvin{{cite journal | last1 = Katz | first1 = Thomas J. | last2 = McGinnis | first2 = James | title = Mechanism of the olefin metathesis reaction | journal = Journal of the American Chemical Society| volume = 97 | issue=6 | pages = 1592–1594 | year = 1975 | doi = 10.1021/ja00839a063| bibcode = 1975JAChS..97.1592K }} He reacted a mixture of cyclooctene, 2-butene and 4-octene with a molybdenum catalyst and observed that the unsymmetrical C14 hydrocarbon reaction product is present right from the start at low conversion.

:Image:MetathesisKatz.svg

In any of the pairwise mechanisms with olefin pairing as rate-determining step this compound, a secondary reaction product of C12 with C6, would form well after formation of the two primary reaction products C12 and C16.

In 1974 Casey was the first to implement carbenes into the metathesis reaction mechanism:{{cite journal | last1 = Casey | first1 = Charles P. | last2 = Burkhardt | first2 = Terry J. | title = Reactions of (diphenylcarbene)pentacarbonyltungsten(0) with alkenes. Role of metal-carbene complexes in cyclopropanation and olefin metathesis reactions | journal = Journal of the American Chemical Society| volume = 96 |issue=25| pages = 7808–7809 | year = 1974 | doi = 10.1021/ja00832a032| bibcode = 1974JAChS..96.7808C }}

:Image:MetathesisCasey1974.svg

Grubbs in 1976 provided evidence against his own updated pairwise mechanism:

:Image:MetathesisPairWiseMechanism.svg

with a 5-membered cycle in another round of isotope labeling studies in favor of the 4-membered cycle Chauvin mechanism:{{cite journal |last1=Grubbs |first1=Robert H. |last2=Burk |first2=Patrick L. |last3=Carr |first3=Dale D. |title=Mechanism of the olefin metathesis reaction |year=1975 |journal=Journal of the American Chemical Society|volume= 97|issue= 11 |pages= 3265–3267 |doi=10.1021/ja00844a082|bibcode=1975JAChS..97.3265G }}{{cite journal | last1 = Grubbs | first1 = Robert H. | last2 = Carr | first2 = D. D. | last3 = Hoppin | first3 = C. | last4 = Burk | first4 = P. L. | title = Consideration of the mechanism of the metal catalyzed olefin metathesis reaction | journal = Journal of the American Chemical Society| volume = 98 |issue=12| pages = 3478–3483 | year = 1976 | doi = 10.1021/ja00428a015| bibcode = 1976JAChS..98.3478G }}

:Image:Metathesisgrubbs1976.svg

In this reaction the ethylene product distribution $(d\_4,d\_2,d\_0)$ at low conversion was found to be consistent with the carbene mechanism. On the other hand, Grubbs did not rule out the possibility of a tetramethylene intermediate.

The first practical metathesis system was introduced in 1978 by Tebbe based on the (what later became known as the) Tebbe reagent.{{cite journal | last1 = Tebbe | first1 = F. N. | last2 = Parshall | first2 = G. W. | last3 = Reddy | first3 = G. S. | title = Olefin homologation with titanium methylene compounds | journal = Journal of the American Chemical Society| volume = 100 |issue=11| pages = 3611–3613 | year = 1978 | doi = 10.1021/ja00479a061| bibcode = 1978JAChS.100.3611T }} In a model reaction isotopically labeled carbon atoms in isobutene and methylenecyclohexane switched places:

:Image:MetathesisTebbe.svg

The Grubbs group then isolated the proposed metallacyclobutane intermediate in 1980 also with this reagent together with 3-methyl-1-butene:{{cite journal | last1 = Howard | first1 = T. R. | last2 = Lee | first2 = J. B. | last3 = Grubbs | first3 = R. H. | title = Titanium metallacarbene-metallacyclobutane reactions: stepwise metathesis | journal = Journal of the American Chemical Society| volume = 102 | issue=22 | pages = 6876–6878 | year = 1980 | doi = 10.1021/ja00542a050| bibcode = 1980JAChS.102.6876H }}

:Image:MetathesisGrubbs1980.svg

They isolated a similar compound in the total synthesis of capnellene in 1986:{{cite journal | last1 = Stille | first1 = John R. | last2 = Grubbs | first2 = Robert H. | title = Synthesis of (.+-.)-.DELTA.9,12-capnellene using titanium reagents | journal = Journal of the American Chemical Society| volume = 108 | pages = 855–856 | year = 1986 | doi = 10.1021/ja00264a058 | issue = 4| bibcode = 1986JAChS.108..855S }}

:Image:MetathesisGrubbs1986.svg

In that same year the Grubbs group proved that metathesis polymerization of norbornene by Tebbe's reagent is a living polymerization system{{cite journal | last1 = Gilliom | first1 = Laura R. | last2 = Grubbs | first2 = Robert H. | title = Titanacyclobutanes derived from strained, cyclic olefins: the living polymerization of norbornene | journal = Journal of the American Chemical Society| volume = 108 |issue=4| pages = 733–742 | year = 1986 | doi = 10.1021/ja00264a027| bibcode = 1986JAChS.108..733G }} and a year later Grubbs and Schrock co-published an article describing living polymerization with a tungsten carbene complex{{cite journal | last1 = Schrock | first1 = R. R. | last2 = Feldman | first2 = J. | last3 = Cannizzo | first3 = L. F. | last4 = Grubbs | first4 = R. H. | title = Ring-opening polymerization of norbornene by a living tungsten alkylidene complex | journal = Macromolecules| volume = 20 |issue=5| pages = 1169–1172 | year = 1987 | doi = 10.1021/ma00171a053|bibcode = 1987MaMol..20.1169S }} While Schrock focussed his research on tungsten and molybdenum catalysts for olefin metathesis, Grubbs started the development of catalysts based on ruthenium, which proved to be less sensitive to oxygen and water and therefore more functional group tolerant.

{{Main|Grubbs catalyst}}

In the 1960s and 1970s various groups reported the ring-opening polymerization of norbornene catalyzed by hydrated trichlorides of ruthenium and other late transition metals in polar, protic solvents.{{cite journal | first1 = Francis W. | last1 = Michelotti | first2 = William P. | last2 = Keaveney | journal = Journal of Polymer Science Part A: General Papers| volume = 3 | issue = 3 | pages = 895–905 | year = 1965 | title = Coordinated Polymerization of the Bicyclo-(2.2.1)-heptene-2 Ring System (Norbornene) in Polar Media | doi=10.1002/pol.1965.100030305}}{{cite journal | first1 = Robert E. | last1 = Rinehart | first2 = Homer P. | last2 = Smith | title = The Emulsion Polymerization of the Norbornene Ring System Catalyzed by Noble Metal Compounds | journal = Journal of Polymer Science Part B: Polymer Letters| volume = 3 | issue = 12 | pages = 1049–1052 | year = 1965 | doi=10.1002/pol.1965.110031215|bibcode = 1965JPoSL...3.1049R }}{{cite journal | first1 = Lido | last1 = Porri | first2 = Renzo | last2 = Rossi | first3 = Pietro | last3 = Diversi | first4 = Antonio | last4 = Lucherini | title = Ring-Opening Polymerization of Cycloolefins with Catalysts Derived from Ruthenium and Iridium | journal = Die Makromolekulare Chemie| volume = 175 | pages = 3097–3115 | year = 1974 | doi=10.1002/macp.1974.021751106 | issue = 11}} This prompted Robert H. Grubbs and coworkers to search for well-defined, functional group tolerant catalysts based on ruthenium. The Grubbs group successfully polymerized the 7-oxo norbornene derivative using ruthenium trichloride, osmium trichloride as well as tungsten alkylidenes.{{cite journal | last1 = Novak | first1 = Bruce M. | last2 = Grubbs | first2 = Robert H. | title = The ring opening metathesis polymerization of 7-oxabicyclo[2.2.1]hept-5-ene derivatives: a new acyclic polymeric ionophore | journal = Journal of the American Chemical Society| volume = 110| issue=3 | pages = 960–961 | year = 1988 | doi = 10.1021/ja00211a043| bibcode = 1988JAChS.110..960N }}

They identified a Ru(II) carbene as an effective metal center and in 1992 published the first well-defined, ruthenium-based olefin metathesis catalyst, (PPh₃)₂Cl₂Ru=CHCH=CPh₂:{{cite journal | last1 = Nguyen | first1 = Sonbinh T. | last2 = Johnson | first2 = Lynda K. | last3 = Grubbs | first3 = Robert H. | last4 = Ziller | first4 = Joseph W. | title = Ring-opening metathesis polymerization (ROMP) of norbornene by a Group VIII carbene complex in protic media | journal = Journal of the American Chemical Society| volume = 114 | issue=10 | pages = 3974–3975 | year = 1992 | doi = 10.1021/ja00036a053| bibcode = 1992JAChS.114.3974N | url = https://authors.library.caltech.edu/88217/2/ja00036a053_si_001.pdf }}

:Image:MetathesisGrubbs1992.svg

The corresponding tricyclohexylphosphine complex (PCy₃)₂Cl₂Ru=CHCH=CPh₂ was also shown to be active.{{cite journal | last1 = Nguyen | first1 = Sonbinh T. | last2 = Grubbs | first2 = Robert H. | last3 = Ziller | first3 = Joseph W. | title = Syntheses and activities of new single-component, ruthenium-based olefin metathesis catalysts | journal = Journal of the American Chemical Society| volume = 115 |issue=21| pages = 9858–9859 | year = 1993 | doi = 10.1021/ja00074a086| bibcode = 1993JAChS.115.9858N }}

This work culminated in the now commercially available 1st generation Grubbs catalyst.{{cite journal | last1 = Schwab | first1 = Peter | last2 = France | first2 = Marcia B. | last3 = Ziller | first3 = Joseph W. | last4 = Grubbs | first4 = Robert H. | title = A Series of Well-Defined Metathesis Catalysts–Synthesis of [RuCl₂(CHR′)(PR₃)₂] and Its Reactions | journal = Angewandte Chemie International Edition in English| volume = 34 | pages = 2039–2041 | year = 1995 | doi = 10.1002/anie.199520391 | issue = 18}}{{cite journal | last1 = Schwab | first1 = Peter | last2 = Grubbs | first2 = Robert H. | last3 = Ziller | first3 = Joseph W. | title = Synthesis and Applications of RuCl₂(=CHR')(PR₃)₂: The Influence of the Alkylidene Moiety on Metathesis Activity | journal = Journal of the American Chemical Society| volume = 118 | pages = 100–110 | year = 1996 | issue = 1 | doi = 10.1021/ja952676d| bibcode = 1996JAChS.118..100S }}

Schrock entered the olefin metathesis field in 1979 as an extension of work on tantalum alkylidenes.{{cite journal | last1 = Schrock | first1 = R. R. | last2 = Meakin | first2 = P. | title = Pentamethyl complexes of niobium and tantalum | journal = Journal of the American Chemical Society| volume = 96 | issue=16 | pages = 5288–5290 | year = 1974 | doi = 10.1021/ja00823a064| bibcode = 1974JAChS..96.5288S }} The initial result was disappointing as reaction of {{chem2|CpTa(\dCH\st\sBu)Cl2}} with ethylene yielded only a metallacyclopentane, not metathesis products:{{cite journal | last1 = McLain | first1 = S. J. | last2 = Wood | first2 = C. D. | last3 = Schrock | first3 = R. R. | title = Preparation and characterization of tantalum(III) olefin complexes and tantalum(V) metallacyclopentane complexes made from acyclic α olefins | journal = Journal of the American Chemical Society| volume = 101 | issue=16 | pages = 4558–4570 | year = 1979 | doi = 10.1021/ja00510a022| bibcode = 1979JAChS.101.4558M }}

:Image:MetathesisSchrock1979.svg

But by tweaking this structure to a {{chem2|PR3Ta(CHt\sbu)(Ot\sbu)2Cl}} (replacing chloride by t-butoxide and a cyclopentadienyl by an organophosphine, metathesis was established with cis-2-pentene.{{cite journal | last1 = Schrock | first1 = R | title = Preparation and characterization of active niobium, tantalum and tungsten metathesis catalysts | journal = Journal of Molecular Catalysis| volume = 8 |issue=1–3| pages = 73–83 | year = 1980 | doi = 10.1016/0304-5102(80)87006-4 | last2 = Rocklage | first2 = Scott | last3 = Wengrovius | first3 = Jeffrey | last4 = Rupprecht | first4 = Gregory | last5 = Fellmann | first5 = Jere}} In another development, certain tungsten oxo complexes of the type {{chem2|W(O)(CHt\sBu)(Cl)2(PEt)3}} were also found to be effective.{{cite journal | last1 = Wengrovius | first1 = Jeffrey H. | last2 = Schrock | first2 = Richard R. | last3 = Churchill | first3 = Melvyn Rowen | last4 = Missert | first4 = Joseph R. | last5 = Youngs | first5 = Wiley J. | title = Multiple metal-carbon bonds. 16. Tungsten-oxo alkylidene complexes as olefins metathesis catalysts and the crystal structure of W(O)(CHCMe₃(PEt₃)Cl₂| journal = Journal of the American Chemical Society| volume = 102|issue=13 | pages = 4515–4CF6 | year = 1980 | doi = 10.1021/ja00533a035| bibcode = 1980JAChS.102.4515W }}

Schrock alkylidenes for olefin metathesis of the type {{chem2|Mo(NAr)(CHC(CH3)2R){OC(CH3)(CF3)2}2}} were commercialized starting in 1990.{{cite journal | last1 = Schrock | first1 = Richard R. | last2 = Murdzek | first2 = John S. | last3 = Bazan | first3 = Gui C. | last4 = Robbins | first4 = Jennifer | last5 = Dimare | first5 = Marcello | last6 = O'Regan | first6 = Marie | title = Synthesis of molybdenum imido alkylidene complexes and some reactions involving acyclic olefins | journal = Journal of the American Chemical Society| volume = 112 | issue=10 | pages = 3875–3886 | year = 1990 | doi = 10.1021/ja00166a023| bibcode = 1990JAChS.112.3875S }}{{cite journal | last1 = Bazan | first1 = Guillermo C. | last2 = Oskam | first2 = John H. | last3 = Cho | first3 = Hyun Nam | last4 = Park | first4 = Lee Y. | last5 = Schrock | first5 = Richard R. | title = Living Ring-Opening Metathesis Polymerization of 2,3-Difunctionalized 7-Oxanorbornenes and 7-Oxanorbornadienes by Mo(CHCMe₂R)(N-2,6-C₆H₃-i-Pr₂)(O-t-Bu)₂ and Mo(CHCMe₂R)(N-2,6-C₆H₃-i-Pr₂)(OCMe₂CF₃)₂ | volume = 113 | issue=18 | pages = 6899–6907 | year = 1991 | doi = 10.1021/ja00018a028}}

:Image:SchrockCatalyst.svg

The first asymmetric catalyst followed in 1993{{cite journal | last1 = McConville | first1 = David H. | last2 = Wolf | first2 = Jennifer R. | last3 = Schrock | first3 = Richard R. | title = Synthesis of chiral molybdenum ROMP initiators and all-cis highly tactic poly(2,3-(R)2norbornadiene) (R = CF₃ or CO₂Me) | journal = Journal of the American Chemical Society| volume = 115 | issue=10 | pages = 4413–4414 | year = 1993 | doi = 10.1021/ja00063a090| bibcode = 1993JAChS.115.4413M }}

:Image:MetathesisROMPSchrock1993.svg

With a Schrock catalyst modified with a BINOL ligand in a norbornadiene ROMP leading to highly stereoregular cis, isotactic polymer.

• Alkane metathesis
• Alkyne metathesis
• Enyne metathesis
• Salt metathesis reaction

{{Reflist}}

1. {{cite journal | doi = 10.1021/cen-v080n016.p029 | title = Olefin Metathesis: Big-Deal Reaction | year = 2002 | volume = 80 | issue = 51 | pages = 29–33 | url = http://pubs.acs.org/cen/coverstory/8051/8051olefin.html}}
2. {{cite journal | title = Olefin Metathesis: The Early Days | year = 2002 | volume = 80 | issue = 51 | pages = 34–38 | url = http://pubs.acs.org/cen/coverstory/8051/8051olefin2.html | doi = 10.1021/cen-v080n029.p034}}
3. {{cite journal |last=Schrock |first=R. R. |author-link=Richard R. Schrock |year=1990 |title=Living ring-opening metathesis polymerization catalyzed by well-characterized transition-metal alkylidene complexes |journal= Accounts of Chemical Research|volume=23 |issue=5 |pages=158–165 |doi=10.1021/ar00173a007 }}
4. {{cite journal |last=Schrock |first=R. R. |author-link=Richard R. Schrock |author2=Hoveyda, A. H. |year=2003 |title=Molybdenum and Tungsten Imido Alkylidene Complexes as Efficient Olefin-Metathesis Catalysts |journal= Angewandte Chemie International Edition|volume=42 |issue=38 |pages=4592–4633 |doi=10.1002/anie.200300576 |pmid=14533149 |s2cid=35370749 }}
5. {{cite journal |last=Samojłowicz |first=C. |author2=Grela, K. |year=2009 |title=Ruthenium-Based Olefin Metathesis Catalysts Bearing N-Heterocyclic Carbene Ligands |journal= Chemical Reviews|pmid=19534492 |volume=109 |issue=8 |pages=3708–3742 |doi=10.1021/cr800524f }}
6. {{cite journal |last=Vougioukalakis |first=G. C. |author2=Grubbs, R. H. |author-link2=Robert H. Grubbs |year=2010 |title=Ruthenium-Based Heterocyclic Carbene-Coordinated Olefin Metathesis Catalysts |journal= Chemical Reviews|pmid=20000700 |volume=110 |issue=3 |pages=1746–1787 |doi=10.1021/cr9002424 |s2cid=4589661 }}
7. {{cite journal |last=Trnka |first=T. M. |author2=Grubbs, R. H. |author-link2=Robert H. Grubbs |year=2001 |title=The Development of L2X2Ru=CHR Olefin Metathesis Catalysts: An Organometallic Success Story |journal= Accounts of Chemical Research|volume=34 |issue=1 |pages=18–29 |doi=10.1021/ar000114f |pmid=11170353|s2cid=22145255 }}
8. {{cite journal |last=Grubbs |first=R. H. |author-link=Robert H. Grubbs |author2=Chang, S. |year=1998 |title=Recent advances in olefin metathesis and its application in organic synthesis |journal= Tetrahedron|volume=54 |issue=18 |pages=4413–4450 |doi=10.1016/S0040-4020(97)10427-6 }}
9. {{cite journal |last=Grubbs |first=R. H. |author-link=Robert H. Grubbs |year=2004 |title=Olefin metathesis |journal= Tetrahedron|volume=60 |issue=34 |pages=7117–7140 |doi= 10.1016/j.tet.2004.05.124 }}
10. {{cite journal |editor-last=Grela |editor-first=K. |year=2010 |title=Progress in metathesis chemistry (Editorial for Open Access Thematic Series)|journal= Beilstein Journal of Organic Chemistry|volume=6 |pages=1089–1090 |doi=10.3762/bjoc.6.124 |pmid=21160917 |pmc=3002079 |last1=Grela |first1=K. }}

{{Alkenes}}

{{Organometallics}}

{{Organic reactions}}

Category:Carbon-carbon bond forming reactions

Category:Organometallic chemistry

Category:Homogeneous catalysis

Category:Industrial processes