Carboxylate-Based Molybdenum Alkylidene Catalysts: Synthesis, Characterization, and Use as Initiators for 1,6-Heptadiyne Cyclopolymerizations

Schrock, Richard R.; Tonzetich, Zachary J.; Lichtscheidl, Alejandro G.; Müller, Péter; Schattenmann, Florian J.

doi:10.1021/om800314y

Cited by 24 publications

(51 citation statements)

References 39 publications

(43 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…31 Schrock and co-workers also prepared various Mo-alkylidene catalysts through reaction of Mo-based trifluoromethanesulfonates with sodium triphenylacetate. 37 These researchers confirmed the formation of 'ate' or not well-defined complexes with the use of small carboxylate ligands as opposed to the use of larger triphenylacetate ligands. 37 Numerous other Mo-based catalysts were synthesized including ones with (TMS) 3 SiCO 2 -ligands.…”

Section: Bidentate or Monodentate Carboxylatesmentioning

confidence: 92%

‘Pseudo-halide’ Derivatives of Grubbs- and Schrock-Type Catalysts for Olefin Metathesis

Anderson¹,

Buchmeiser²

2011

Synlett

View full text Add to dashboard Cite

Metathesis has persisted through the years as a formidable synthetic approach to various unsaturated organic molecules and macromolecules. The 21st century developments in olefin metathesis continue to feature more efficient and selective, well-defined metathesis catalysts. Due to the easily regulated steric and electronic properties of 'pseudo-halide' derivatives, their study has launched a new milestone in ruthenium-and molybdenum-based catalysis. Synthesizing 'pseudo-halide' derivatives often entails replacing halide ligands with easily modified carboxylates, perfluorocarboxylates, phenoxides, isocyanates, isothiocyanates, pyridines, nitrates, and trifluoromethanesulfonates. This account elucidates the recent advances in 'pseudo-halide'-containing olefin metathesis, including synthetic approaches to obtain new catalysts and optimization of the ligand sphere. Several innovations in Ru-and Moalkylidenes that concern initiation efficiency, reactivity, stereoselectivity, supported catalysis, cyclopolymerization, and copolymerization are described. Refinement of the anionic 'pseudo-halide' ligands has enabled the perfection of Ru-and Mo-based metathesis catalysts in both reactivity and selectivity. These advances have led to stereoselectivity in polymerizations, improved copolymerization affinity, and the regioselective cyclopolymerization of 1,6-heptadiynes to result in conjugated polymers solely based on five-membered repeat units.

show abstract

Section: Bidentate or Monodentate Carboxylatesmentioning

confidence: 92%

‘Pseudo-halide’ Derivatives of Grubbs- and Schrock-Type Catalysts for Olefin Metathesis

Anderson¹,

Buchmeiser²

2011

Synlett

View full text Add to dashboard Cite

show abstract

“…A colorless oil (6.23 g, 81%) was isolated after freezedrying. 1 Ethyl ((1R,2S,5S)-2-Isopropyl-5-methylcyclohexyl)cyclopent-3-ene-1,1-dicarboxylate (A). 4-(Ethoxycarbonyl)-4-(1S,2R,5S)-(−)-menthoxycarbonyl-1,6-heptadiene (110 mg, 323.8 μmol) was dissolved in 5 mL of CH 2 Cl 2 .…”

Section: Macromoleculesmentioning

confidence: 99%

“…A colorless oil (97.8 mg, 97%) was obtained. 1 Mo(N-2-t-BuC 6 H 4 )(CHCMe 2 Ph)(2,5-dimethylpyrrolide) 2 (2). A solution of Mo(N-2-t-BuC 6 H 4 )(CHCMe 2 Ph)(OTf) 2 (DME) (280 mg, 0.389 mmol) in 50 mL of diethyl ether was chilled to −30°C, and lithium-2,5-dimethylpyrrolide (80.6 mg, 0.798 mmol) was added slowly.…”

Section: Macromoleculesmentioning

confidence: 99%

“…For first-generation Schrock initiators, the concept of large and small alkoxides was developed by the Schrock group and allowed for the selective β-addition of monomer. 1,2 Our group was capable of extending this concept to selective α-addition by using first-generation Schrock initiators bearing small alkoxides, an additional coordinating base, and low temperatures. 18,[20][21][22][23][24]30,31 In that context not only the alkoxide but also the imido ligands played a predominant role in the control of the regioselectivity.…”

Section: ■ Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mechanism of the Regio- and Stereoselective Cyclopolymerization of 1,6-Hepta- and 1,7-Octadiynes by High Oxidation State Molybdenum–Imidoalkylidene N-Heterocyclic Carbene Initiators

Herz¹,

Unold

Hänle³

et al. 2015

Macromolecules

View full text Add to dashboard Cite

The regio-and stereoselective cyclopolymerization of a series of 1,6-heptadiynes and 1,7-octadiynes, i.(MAP3) is described. With initiators I1−I4, high regioselectivity >96% was observed in the polymerization of M1−M4, allowing for virtually selective α-insertion. These initiators displayed also high stereoselectivity, allowing for all-trans polyenes with up to 96% syndioselectivity. By contrast, the MAP initiators MAP1−MAP3 showed poor regioselectivity (26−62% α-selectivity). A polymerization mechanism is proposed that explains for the high stereo-and regioselectivity of the Mo− imidoalkylidene NHC complexes. ■ INTRODUCTIONThe cyclopolymerization of 1,6-hepta-and 1,7-octadiynes has been widely used for the syntheses of soluble, conjugated polymers possessing a rigid backbone. 1−29 Equally important, it can also be used as a probe to determine both the regio-and stereoselectivity of insertion and to come up with a polymerization mechanism for a specific initiator system. Two different pathways for the cyclopolymerization of α,ω-diynes with Schrock-type molybdenum carbenes exist (Scheme 1). 3,4 Thus, the monomer can undergo either α-or β-addition. The first addition step of the monomer to the metal alkylidene is decisive for the structure of the resulting repeat unit. In the absence of any backbiting, the polymer structure is a concise record of all previous insertion steps. For first-generation Schrock initiators, the concept of large and small alkoxides was developed by the Schrock group and allowed for the selective β-addition of monomer. 1,2 Our group was capable of extending this concept to selective α-addition by using first-generation Schrock initiators bearing small alkoxides, an additional coordinating base, and low temperatures. 18,[20][21][22][23][24]30,31 In that context not only the alkoxide but also the imido ligands played a predominant role in the control of the regioselectivity. 32,33 Recently, molybdenum−imidoalkylidene NHC bis(triflate) 34 and cationic tungsten−oxoalkylidene NHC complexes 35 have been developed in our group. Particularly molybdenum− imidoalkylidene NHC bistriflates display high reactivity for various norborn-2-enes, 7-oxanorborn-2-enes, and diynes and are also tolerant toward nitrile, amino, hydroxyl, and carboxylic acid groups. 34 We were interested in the polymerization mechanism that applies in the polymerization of α,ω-diynes with these novel initiators. Equally important, we wished to find out about the stereo-and regioselectivity of these novel complexes and therefore addressed the issues of tacticity and cis/trans selectivity in cyclopolymerization. Since the cationic species derived from Mo−imidoalkylidene NHC bis(triflate) complexes resemble to some extent molybdenum−imidoalkylidene monoalkoxide monopyrrolide (MAP) catalysts developed by the Schrock group, 36,37 and since these systems have

show abstract

“…Molybdenum imido alkylidene complexes that contain bulky carboxylate ligands have been prepared and evaluated for the cyclopolymerizations of 1,6-heptadiynes [73]. Examples include: Mo(NR)(CHCMe 2 Ph)(O 2 CCPh 3 ) 2 (R = Ad, Ar, Ar Me2 ), Mo(NAr Me2 )(CH-t-Bu)(O 2 CCPh 3 ) 2 (R = Ar Me2 , Ar Cl ), and Mo(NAr)(CHCMe 2 Ph)(O 2 CR ′′ ) 2 (R ′′ = CMePh 2 , Si(SiMe 3 ) 3 ).…”

Section: Other Constructsmentioning

confidence: 99%

High‐Oxidation State Molybdenum and Tungsten Complexes Relevant to Olefin Metathesis

Schrock

2015

Handbook of Metathesis

Self Cite

View full text Add to dashboard Cite

The first examples of high-oxidation state ("d 0 ") alkylidene and alkylidyne complexes (of tantalum) were published in 1974 and 1975 [1]. Several years of research were required to show that the principles behind tantalum chemistry could be employed to prepare alkylidene and alkylidyne complexes of Mo, W, and Re in their highest oxidation states (counting the alkylidene as a dianionic ligand and the alkylidyne as a trianionic ligand), and that these high-oxidation state complexes, especially those that contain one or more alkoxide ligands, are efficient catalysts for alkene and alkyne metathesis reactions, respectively. This process has been described in previous reviews [2]. Applications of high-oxidation state catalysts for alkene and alkyne metathesis in organic chemistry have also been reviewed [3], although each of these subjects is reviewed again elsewhere in this series in view of the many recent advancements. This review will focus on isolated and characterized high-oxidation state molybdenum and tungsten alkylidene and metallacyclobutane complexes. Attention will be directed largely toward monoalkoxide pyrrolide (MAP) complexes because they have yielded the majority of new results in the last several years. MAP species have been found to be especially efficient in several Z-selective olefin metathesis reactions, such as homocoupling, cross-coupling, ethenolysis, and ROMP (see Grubbs, Handbook of Metathesis, 2nd Edition, Volume 2, Chapter 7). Most of what is presented here has appeared since a review in 2009 [4].In the last decade, impressive advances have been made in the synthesis of alkylidene and alkylidyne complexes that contain metals from groups 4 [5] and 5 [5i,j,m, 6], especially Ti and V, but -except for the ROMP of norbornene by vanadium complexes -group 4 and 5 metals have not shown wide-ranging activity for olefin metathesis. Well-characterized rhenium(VII) complexes are known to be active for metathesis, and many rhenium(VII) alkylidene and alkylidyne complexes have been isolated [2a], but little attention has been paid to the syntheses of rhenium alkylidene or alkylidyne complexes in the last decade. Theoretical calculations have been carried out on M(X)(CHR ′ )(Y)(Z) complexes

show abstract

Carboxylate-Based Molybdenum Alkylidene Catalysts: Synthesis, Characterization, and Use as Initiators for 1,6-Heptadiyne Cyclopolymerizations

Cited by 24 publications

References 39 publications

‘Pseudo-halide’ Derivatives of Grubbs- and Schrock-Type Catalysts for Olefin Metathesis

‘Pseudo-halide’ Derivatives of Grubbs- and Schrock-Type Catalysts for Olefin Metathesis

Mechanism of the Regio- and Stereoselective Cyclopolymerization of 1,6-Hepta- and 1,7-Octadiynes by High Oxidation State Molybdenum–Imidoalkylidene N-Heterocyclic Carbene Initiators

High‐Oxidation State Molybdenum and Tungsten Complexes Relevant to Olefin Metathesis

Contact Info

Product

Resources

About