In recent years, the olefin metathesis reaction has attracted widespread attention as a versatile carbon−carbon bond-forming method. Many new applications have become possible because of major advances in catalyst design. State-of-the-art ruthenium catalysts are not only highly active but also compatible with most functional groups and easy to use. This Account traces the ideas and discoveries that were instrumental in the development of these catalysts, with particular emphasis on (PCy3)2Cl2RuCHPh and its derivatives. The discussion includes an analysis of trends in catalyst activity, a description of catalysts coordinated with N-heterocyclic carbene ligands, and an overview of ongoing work to improve the activity, stability, and selectivity of this family of L2X2RuCHR complexes.

http://web4.uwindsor.ca/users/j/jlichaa/reference.nsf/0/10ff8b04ff3a317885256d88005720f6/$FILE/acr-2001-34-18-metath-grubbs.pdf

The Development of L2X2RuCHR Olefin Metathesis Catalysts: An Organometallic Success Story

The fascinating story of olefin (or alkene) metathesis (eq
1) began almost five decades ago, when Anderson and
Merckling reported the first carbon-carbon double-bond
rearrangement reaction in the titanium-catalyzed polymerization of norbornene. Nine years later, Banks and Bailey reported “a new disproportionation reaction . . . in which olefins are converted to homologues of shorter and longer carbon chains...”. In 1967, Calderon and co-workers named this metal-catalyzed redistribution of carbon-carbon double bonds olefin metathesis, from the Greek word “μeτάθeση”, which means change of position. These contributions have since served as the foundation for an amazing research field, and olefin metathesis currently represents a powerful transformation in chemical synthesis, attracting a vast amount of interest both in industry and academia.

https://core.ac.uk/download/pdf/4884240.pdf

Ruthenium-based heterocyclic carbene-coordinated olefin metathesis catalysts.

The advent of well-defined catalysts for olefin metathesis which combine high activity, durability, and excellent tolerance towards polar functional groups has revolutionized the field. The past decade has seen the rapid embrace of these reagents as tools for advanced organic and polymer chemistry and the success of this development is witnessed by a plethora of elegant applications to the synthesis of natural and nonnatural products. This review article provides an overview of these developments and intends to familiarize the reader with some very recent advances which hold the promise to expand the scope of the reaction even further. Moreover, the positive impact of metathesis on the fundamental logic of retrosynthetic planning is demonstrated by means of typical examples. Finally, it will be shown that metathesis is by no means restricted to alkenes as substrates, and some comments on metathesis reactions following unconventional mechanistic pathways will also be presented.

Olefin Metathesis and Beyond

Living ring-opening metathesis polymerization

Catalytic olefin metathesis has quickly emerged as one of the most often-used transformations in modern chemical synthesis. One class of catalysts that has led the way to this significant development are the high-oxidation-state alkylidene complexes of molybdenum. In this review key observations that resulted in the discovery and development of molybdenum- and tungsten-based metathesis catalysts are outlined. An account of the utility of molybdenum catalysts in the synthesis of biologically significant molecules is provided as well. Another focus of the review is the use of chiral molybdenum complexes for enantioselective synthesis. These highly efficient catalysts provide unique access to materials of exceptional enantiomeric purity and often without generating solvent waste.

Molybdenum and tungsten imido alkylidene complexes as efficient olefin-metathesis catalysts.

Addition of LiDIPP = O-2,6-C{sub 6}H{sub 3}-i-Pr{sub 2} to Ta(CH-t-Bu)(THF){sub 2}Cl{sub 3} yields Ta(CH-t-Bu)(DIPP){sub 3}(THF) (1) in high yield. Ta(CH-t-Bu)(DMP){sub 3}(THF) (3; DMP = O-2,6-C{sub 6}H{sub 3}Me{sub 2}) and Ta(CH-t-Bu)(TIPT){sub 3}(THF) (5; TIPT = S-,2,4,6-C{sub 6}H{sub 2}i-Pr{sub 3}) can be prepared by analogous methods. 1 reacts rapidly with 1 equiv of styrene to give the tantalacyclobutane complex Ta(CH(Ph)CH(t-Bu)CH{sub 2})(DIPP){sub 3}. The crystal and molecular structure of the complex are reported. An analogous reaction between 1 and vinyltrimethylsilane gives Ta(CHSiMe{sub 3})(DIPP){sub 3}(THF) or Ta(CH(SiMe{sub 3})CH(SiMe{sub 3})CH{sub 2})(DIPP){sub 3} depending upon reaction conditions; the two are in ready equilibrium. 1 reacts smoothly with ethylene to give Ta(CH{sub 2}CH{sub 2}CH{sub 2})(DIPP){sub 3} in high yield, but treatment of 1 with olefins such as propylene or 1-butene did not lead to any characterizable species. Addition of excess cis-2-pentene to 1 results in rapid metathesis (100 equiv to equilibrium in < 15 min), but activity is short-lived. In contrast to reactions between 1 and olefins, Ta(CH-t-Bu)(TIPT){sub 3}(THF) does not react with ordinary olefins and will not metathesize them. Tantalacyclobutane complexes containing the DIPP ligand react with the carbonyl functionality to give a mixture of insertion chemistry (oxytantalacyclohexane complexes) and Wittig-like reactivity, depending upon the carbonylmore » compound, the tantalacycle, and the temperature. 1 reacts with norbornene to give an isolable tantalacyclobutane complex, Ta(CH(C{sub 5}H{sub 8})CHCH(t-Bu))(DIPP){sub 3}, whose crystal structure is reported. 25 references, 9 figures, 7 tables.« less

Preparation and reactions of tantalum alkylidene complexes containing bulky phenoxide or thiolate ligands. Controlling ring-opening metathesis polymerization activity and mechanism through choice of anionic ligand

Simple routes to mono(.eta.5-pentamethylcyclopentadienyl) complexes of molybdenum(V) and tungsten(V)

(MoCp{sup *}Cl{sub 4}){sub 2} (Cp{sup *} = C{sub 5}Me{sub 5}) is alkylated by MeMgCl in tetrahydrofuran to give red microcrystalline MoCp{sup *}Me{sub 4} in {approximately}70% yield. MoCp{sup *}Me{sub 4} reacts with 1 equiv of HOSO{sub 2}CF{sub 3} in ether to give purple microcrystalline MoCp{sup *}Me{sub 3}(OSO{sub 2}CF{sub 3}) in {approximately}85% yield. Triflate can be displaced readily from MoCp{sup *}Me{sub 3}(OSO{sub 2}Cf{sub 3}) by adding LiOR (OR = pentafluorophenoxide, 2,6-diisopropylphenoxide, 2,6-dimethoxyphenoxide, 2,4,6-trimethoxyphenoxide, 2,6-dimethyl-4-methoxyphenoxide, and catecholate) in ether to yield complexes of the type MoCp{sup *}Me{sub 3}(OR) (MoCp{sup *}Me{sub 2}(cat) in the case of catecholate) in 50-80% yield. The complexes can be oxidized chemically (with the exception of OR = pentafluorophenoxide and catecholate) by (FeCp{sub 2})(PF{sub 6}) in methylene chloride to give complexes of the type (MoCp{sup *}Me{sub 3}(OR))(PF{sub 6}) as orange-brown microcrystalline powders in 80-90% yield. Addition of 3 equiv of hydrazine to (MoCp{sup *}Me{sub 3}(OR))(PF{sub 6}) in ether provides (MoCp{sup *}Me{sub 3}){sub 2}({mu}-N{sub 2}) in low yield after purification by filtration through alumina and recrystallization from ether. (MoCp{sup *}Me{sub 3}){sub 2}({mu}-N{sub 2}) belongs to the space group P2{sub 1}/n.

Preparation and characterization of two high oxidation state molybdenum dinitrogen complexes: [MoCp*Me3]2(.mu.-N2) and [MoCp*Me3](.mu.-N2)[WCp'Me3]

A study of high-oxidation-state complexes of the type [W(.eta.5-C5Me5)Me2X]2(.mu.-N2), including x-ray structures of [W(.eta.5-C5Me5)Me2(OC6F5)]2(.mu.-N2) and [W(.eta.5-C5Me5)Me2(S-2,4,6-C6H2Me3)]2(.mu.-N2)

Les deux composes du titre cristallisent dans le systeme monoclinique, groupe d'espace C2/c pour le premier et P2 1 n pour le second

Thiolato dinitrogen (or hydrazido(4-)) complexes, [Ta(SAr)3(THF)]2(.mu.-N2) (Ar = 2,6-C6H3-iso-Pr2, 2,4,6-C6H2-iso-Pr3), and phenoxide analogs. A structural comparison of [Ta(S-2,6-C6H3-iso-Pr2)3(THF)]2(.mu.-N2), and [Ta(O-2,6-C6H3-iso-Pr2)3(THF)]2(.mu.-N2)

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Preparation and reactions of tantalum alkylidene complexes containing bulky phenoxide or thiolate ligands. Controlling ring-opening metathesis polymerization activity and mechanism through choice of anionic ligand

Simple routes to mono(.eta.5-pentamethylcyclopentadienyl) complexes of molybdenum(V) and tungsten(V)

Preparation and characterization of two high oxidation state molybdenum dinitrogen complexes: [MoCpMe3]2(.mu.-N2) and [MoCpMe3](.mu.-N2)[WCp'Me3]

A study of high-oxidation-state complexes of the type [W(.eta.5-C5Me5)Me2X]2(.mu.-N2), including x-ray structures of [W(.eta.5-C5Me5)Me2(OC6F5)]2(.mu.-N2) and [W(.eta.5-C5Me5)Me2(S-2,4,6-C6H2Me3)]2(.mu.-N2)

Thiolato dinitrogen (or hydrazido(4-)) complexes, [Ta(SAr)3(THF)]2(.mu.-N2) (Ar = 2,6-C6H3-iso-Pr2, 2,4,6-C6H2-iso-Pr3), and phenoxide analogs. A structural comparison of [Ta(S-2,6-C6H3-iso-Pr2)3(THF)]2(.mu.-N2), and [Ta(O-2,6-C6H3-iso-Pr2)3(THF)]2(.mu.-N2)