Synthesis of Molybdenum Dicarbonyl Complexes Bearing Tethered Homoallylic Amines and Sulfides

Krafft, Marie E.; Procter, Martin J.; Abboud, Khalil A.

doi:10.1021/om9807102

Cited by 12 publications

(8 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar displacements were observed in the 13 C NMR spectra, where the signals assigned to the olefinic carbons in compounds 18 and 19 are shifted to high field compared with those found for 5a and 7a derivatives, as expected for a higher sp 3 character of both carbon atoms, consistent with a η 2 -olefin−M interaction. The values agree well with those reported for related group 6 organometallic complexes. , Thus, for [Mo(η 5 -C 5 H 5 )Cl(CO){PPh 2 (C 6 H 4 -η 2 -CHCHCH 3 )}],7a resonances in the 13 C NMR spectrum (dichloromethane- d 2 ) at δ 90.44 and 66.0 are assigned to CH and  C HCH 3 carbon atoms, respectively, of the olefin coordinated to the metal center. Analogous chelate coordination of allyl-dimethylsilyl-η 5 -cyclopentadienyl ligands is known only for group 4 and 5 transition metals.…”

Section: Resultssupporting

confidence: 88%

“…Compared to similar alkyl pendant chains, 2a-c, the higher acidity and fluxional character of the silyl substituents could favor coordination of the alkene to the metallic center . Furthermore, the chelating effect of allyl systems tethered to chelating P, N, or S atoms has already been shown to stabilize the otherwise labile π-alkene early transition metal bonds. , These reasons moved us to undertake similar studies using the allyl-dimethylsilyl-η 5 -cyclopentadienyl ligand with more electron-rich group 6 metal complexes.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Allyl Isomerization Mediated by Cyclopentadienyl Group 6 Metal Compounds

et al. 2007

View full text Add to dashboard Cite

Reactions at mild temperatures of the acetonitrile adducts [M(CO) 3 (NCMe) 3 ] (M ) Mo (1), W (2)) with various substituted cyclopentadienes in THF give the hydrido derivatives 17)) in isolated yields of 60-70%. THF solutions of derivatives 5a, 7a, and 8a undergo isomerization of the cyclopentadienyltethered-allyl unit to give the corresponding methyl-vinyl-dimethylsilyl-η 5 -cyclopentadienyl hydrido compounds) in final a:b ratios of ca. 2:1, 2:1, and 1:1, respectively. Solvent polarity seems to be crucial in these transformations. Dehydrogenation and desilylation of 5a in THF solutions to give the dinuclear derivative [Mo{η 5 -C 5 H 4 Si(CH 3 ) 2 (CH 2 CHdCH 2 )}(CO) 3 ] 2 ( 9) and [MoH(η 5 -C 5 H 5 )(CO) 3 ] (15), respectively, are processes competitive with the allyl isomerization. Treatment of 5a and 7a with equimolar amounts of ONMe 3 permits isolation of pure compound 9 and [W{η 5 -C 5 H 4 Si(CH 3 ) 2 (CH 2 CHdCH 2 )}-(CO) 3 ] 2 (10) in isolated yields of 80-90%. Coordination of the olefin pendant unit to the metal was detectable only by reaction of 5a and 7a with [CPh 3 ][B(C 6 F 5 ) 4 ] to give the cationic species [M{η 5 -C 5 H 4 Si-(CH 3 ) 2 (CH 2 CHdCH 2 )}(CO) 3 ][B(C 6 F 5 ) 4 ] (M ) Mo (18), W ( 19)). Molecular structure determinations by X-ray diffraction methods for derivatives 8a and 9 are also reported.

show abstract

Section: Resultssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Allyl Isomerization Mediated by Cyclopentadienyl Group 6 Metal Compounds

et al. 2007

View full text Add to dashboard Cite

show abstract

“…The availability of suitable starting materials has always been of considerable importance to the synthetic chemist. η 3 -Allyl dicarbonyl complexes of Mo and W play an important role in both coordination chemistry − and catalytic organic transformations, and their reactivity depends on the nature of the ligands completing the coordination sphere. − Since the discovery of pseudooctahedral molybdenum(II) complexes of the type [Mo(η 3 -allyl)X(CO) 2 (CH 3 CN) 2 ] (X = halide) in 1968, a series of derivatives containing the {Mo(η 3 -allyl)(CO) 2 } + moiety has been easily prepared by substitution of the labile nitrile ligands and/or the anion X. ,,,,− In particular, compounds of the type [Mo(η 3 -allyl)X(CO) 2 (N−N)], where N−N = 2,2‘- bipyridine or 1,10-phenanthroline, were found to possess some air and water tolerance. , These compounds have been successfully used as catalyst precursors for imine aziridination, oxidation of triphenylphosphine with molecular oxygen, or as catalysts for allylic alkylations. − Recent studies have revealed that complexes [Mo(η 3 -C 3 H 5 )X(CO) 2 (CH 3 CN) 2 ] act as single component initiators for ring-opening metathesis polymerization of norbornene and polymerization of terminal acetylenes and catalyze the oligomerization of Ph(C⋮C) n Ph ( n = 1, 2) …”

Section: Introductionmentioning

confidence: 99%

Molybdenum η³-Allyl Dicarbonyl Complexes as a New Class of Precursors for Highly Reactive Epoxidation Catalysts with tert-Butyl Hydroperoxide

et al. 2007

View full text Add to dashboard Cite

New Mo(II) diimine derivatives of [Mo(η3-allyl)X(CO)2(CH3CN)2] (allyl = C3H5 and C5H5O; X = Cl, Br) were prepared, and [Mo(η3-C3H5)Cl(CO)2(BIAN)] (BIAN = 1,4-(4-chloro)phenyl-2,3-naphthalenediazabutadiene) (7) was structurally characterized by single-crystal X-ray diffraction. This complex adopted an equatorial−axial arrangement of the bidentate ligand (axial isomer), in contrast with the precursors, found as the equatorial isomer in the solid and fluxional in solution. The new complexes of the type [Mo(η3-allyl)X(CO)2(N−N)] (N−N is a bidentate chelating dinitrogen ligand) were tested for the catalytic epoxidation of cyclooctene using tert-butyl hydroperoxide as oxidant. All catalytic systems were 100% selective toward epoxide formation. While their turnover frequencies paralleled those of related Mo(II) carbonyl compounds or Mo(VI) compounds bearing similar N-donor ligands, they exhibited similar olefin conversions in consecutive catalytic runs. The acetonitrile precursors were generally more active than the diimine complexes, and the chloro derivatives more active than the bromo ones. Combined vibrational and NMR spectroscopy and computational studies (DFT) were used to investigate the nature of the molybdenum species formed in the catalytic system with [Mo(η3-C3H5)Cl(CO)2{1,4-(2,6-dimethyl)phenyl-2,3-dimethyldiazabutadiene}] (4) and to propose that the resulting species may be dimeric bearing oxide bridges.

show abstract

“…No reaction is observed even in the presence of the more reactive diethyl malonate. [280] This observation is readily explained by the lack of feasible pathway from adopted structure D to C, enforced by the allylic tether. Instead, complexes of this type have displayed some preliminary utility in stereoand regioselective reactions with aldehydes to form homoallylic alcohols.…”

Section: Scheme 28mentioning

confidence: 99%

“…For L = SMe the product is unstable but the nature of the thermal decomposition has not been reported. [280] Alternatively, a similar mechanism to allylic alkylation can be envisaged, involving C-C coupling between the dissociated terminus of the η 1 -allylic substrate and the nucleophile bound in a monodentate fashion (Scheme 37). In this case the chelation of the nucleophile (vide supra) may instead simply constitute an intermediate through which C ⇌ D isomerism is executed, in order to place the nucleophile cis to the allylic termini.…”

Section: Scheme 28mentioning

confidence: 99%

η3-Allyl carbonyl complexes of group 6 metals: Structural aspects, isomerism, dynamic behaviour and reactivity

Ryan

Cardin

Hartl

2017

Coordination Chemistry Reviews

View full text Add to dashboard Cite

Contents 1. Introduction 2. Complexes [CpM(CO)2(η 3 -allyl)] and related compounds 2.1. Synthetic strategies 2.2. Exo ⇌ endo isomerism 2.3. 95 Mo and 183 W NMR spectroscopy 2.4. Oxidized cationic complexes -reactivity, fluxionality, structural features 2.5. Mixed nitrosyl carbonyl complexes [CpM(CO)(NO)(η 3 -allyl)] + (M = Mo, W) 3. Complexes [M(CO)2(η 3 -allyl)(α-diimine)X] (X = anionic monodentate ligand) and related compounds 3.1. Synthetic strategies 3.2. Mechanistic features, structural aspects, and dynamic behaviour 3.3. Monodentate ligands bound to M(CO)2(η 3 -allyl)(L⏜L): reactivity and intermediacy in allylic alkylations 3.4. Redox Properties and Electrocatalysis 4. Amidinato and pyrazolato complexes related to [M(CO)2(η 3 -allyl)(α-diimine)X] 4.1. Synthesis and dynamic behaviour 4.2. Coordinatively unsaturated species and their reactivity 5. Summary and outlook Acknowledgement References 2 ABSTRACTTransition metal complexes with π-allylic ligands remain an attractive topic in organometallic chemistry, given the numerous reports of a wide variety of synthetic routes, dynamic behaviour and reactivity, structural (including isomerism), spectroscopic and redox properties, and applications in organic synthesis and catalysis. Surprisingly, despite the considerable interest in the rich and varied chemistry of this family of organometallic compounds, there is no recent review. This review is focused on π-allylic representatives of low-cost Group-6 metals bearing one or more carbonyl ligand, the coordination sphere being complemented with η 5cyclopentadienyl (Section 2), chelating ligands, including redox active α-diimines and various complementary diphosphine (Section 3) and novel anionic amidinate or pyrazolate (Section 4) ligands. In Section 1 particular attention is paid to rearrangements of the π-allylic ligand, namely exo and endo isomerism, interconversion mechanisms, fluxionality, and agostic interactions. In addition, the application of multinuclear NMR spectroscopy to the elucidation of such isomerism, and the effect of the metal centre oxidation state on the bonding, dynamic behaviour and reactivity of the π-allylic ligand are described. The detailed mechanistic description of the synthetic routes and dynamic behaviour of selected representatives of αdiimine complexes in Section 2 is followed by a description of the [M(CO)2(η 3 -allyl-H,R)(αdiimine)] 0/+ fragment as a convenient scaffold for diverse monodentate ligands participating in a range of substitution, insertion, intramolecular migration and C-C coupling reactionsfrequently involving also the π-allylic ligand, such as allylic alkylation. Special attention is devoted to selected examples of redox and acid-base reactivity of the α-diimine complexes with emphasis on prospects in electrocatalysis. The amidinate (and related pyrazolate) ligands treated in Section 4 may directly replace the π-allylic ligand in some cyclopentadienyl complexes (Section 2) or the α-diimine ligand in some dicarbonyl π-allylic complexes (Section 3). The brief description...

show abstract

Synthesis of Molybdenum Dicarbonyl Complexes Bearing Tethered Homoallylic Amines and Sulfides

Cited by 12 publications

References 15 publications

Allyl Isomerization Mediated by Cyclopentadienyl Group 6 Metal Compounds

Allyl Isomerization Mediated by Cyclopentadienyl Group 6 Metal Compounds

Molybdenum η³-Allyl Dicarbonyl Complexes as a New Class of Precursors for Highly Reactive Epoxidation Catalysts with tert-Butyl Hydroperoxide

η3-Allyl carbonyl complexes of group 6 metals: Structural aspects, isomerism, dynamic behaviour and reactivity

Contact Info

Product

Resources

About

Synthesis of Molybdenum Dicarbonyl Complexes Bearing Tethered Homoallylic Amines and Sulfides

Cited by 12 publications

References 15 publications

Allyl Isomerization Mediated by Cyclopentadienyl Group 6 Metal Compounds

Allyl Isomerization Mediated by Cyclopentadienyl Group 6 Metal Compounds

Molybdenum η3-Allyl Dicarbonyl Complexes as a New Class of Precursors for Highly Reactive Epoxidation Catalysts with tert-Butyl Hydroperoxide

η3-Allyl carbonyl complexes of group 6 metals: Structural aspects, isomerism, dynamic behaviour and reactivity

Contact Info

Product

Resources

About

Molybdenum η³-Allyl Dicarbonyl Complexes as a New Class of Precursors for Highly Reactive Epoxidation Catalysts with tert-Butyl Hydroperoxide