First Insertion Reaction of Carbon Monoxide into a Rhenium‐Carbon σ‐Bond

Lindner, Ekkehard; Au, Günter von

doi:10.1002/anie.198008241

Cited by 18 publications

(6 citation statements)

References 5 publications

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“…It is unclear whether the migratory insertion leading from 12 to [ 3-M 1 ] − is Lewis acid-assisted (which would require B−O cleavage). Migratory insertion on Re in the absence of a Lewis acid is very rare and usually slow, , but the reaction here is quite slow compared to the insertions observed following reduction of 2-E 2 and 2-E 2 -Mn . (The analogous reaction in the 2-E 1 Ph 1 system is also faster ; vide infra .)…”

Section: Resultsmentioning

confidence: 74%

“…It should be noted that the observation of [ 9 ] − in C 6 D 5 Cl does not necessarily rule out a migratory insertion mechanism, since bis(carbene) formation could be reversible. Migratory insertion of a carbonyl into a Re−C bond has been reported to proceed with assistance from a (much stronger) Lewis acid . The reduction of [ 1-M 1 ] + ( vide infra ) appears unambiguously to proceed via migratory insertion as well, but that reaction is quite slow.…”

Section: Resultsmentioning

confidence: 99%

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Homogeneous CO Hydrogenation: Ligand Effects on the Lewis Acid-Assisted Reductive Coupling of Carbon Monoxide

2010

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Structure−function studies on the role of pendent Lewis acids in the reductive coupling of CO are reported. Cationic rhenium carbonyl complexes containing zero, one, or two phosphinoborane ligands (Ph2P(CH2) n B(C8H14), n = 1−3) react with the nucleophilic hydride [HPt(dmpe)2]+ to reduce [M−CO]+ to M−CHO; this step is relatively insensitive to the Lewis acid, as both pendent (internal) and external boranes of appropriate acid strength can be used. In contrast, whether a second hydride transfer and C−C bond forming steps occur depends strongly on the number of carbon atoms between P and B in the phosphinoborane ligands, as well as the number of pendent acids in the complex: shorter linker chain lengths favor such reductive coupling, whereas longer chains and external boranes are ineffective. A number of different species containing partially reduced CO groups, whose exact structures vary considerably with the nature and number of phosphinoborane ligands, have been crystallographically characterized. The reaction of [(Ph2P(CH2)2B(C8H14))2Re(CO)4]+ with [HPt(dmpe)2]+ takes place via a “hydride shuttle” mechanism, in which hydride is transferred from Pt to a pendent borane and thence to CO, rather than by direct hydride attack at CO. Addition of a second hydride in C6D5Cl at −40 °C affords an unusual anionic bis(carbene) complex, which converts to a C−C bonded product on warming. These results support a working model for Lewis acid-assisted reductive coupling of CO, in which B (pendent or external) shuttles hydride from Pt to coordinated CO, followed by formation of an intramolecular B−O bond, which facilitates reductive coupling.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Homogeneous CO Hydrogenation: Ligand Effects on the Lewis Acid-Assisted Reductive Coupling of Carbon Monoxide

2010

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“…For the latter, assistance of Al 2 Br 6 is required which yields the adduct (91); hydrolysis of this intermediate gives the acyl product listed next to it in Table 14. 290 The acyl derivative is observed to eliminate CO easily in solution at room temperature.…”

Section: Metallocyclic Derivatives Containing Carbon To Metal Bond(s)mentioning

confidence: 99%

“…489 Migration can be facilitated by the addition of Lewis acid, as recently shown for compounds of manganese. 518 This reaction was successfully applied to a metallocyclic alkyl derivative of rhenium 290 (see (91) in Section 30.6.4). After removal of Lewis acid through hydrolysis the CO is readily lost to restore the original metallocyclic derivative.…”

Section: Carbonyl Insertion {Alkyl Migration)mentioning

confidence: 99%

Technetium and Rhenium

Boag

Kaesz

1982

Comprehensive Organometallic Chemistry

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“…Earlier examples include studies on the formation, properties, and reactivity of metal formyl and related oxycarbene complexes, many of which are stable enough to be isolated; in some cases carbon–carbon bond formation was observed upon reduction of metal-bound CO with hydride equivalents . C–C bond formation was also modeled by studying the migratory insertion of CO into metal–alkyls, which can be promoted by Lewis or Brønsted acidic additives …”

Section: Introductionmentioning

confidence: 99%

A Thermodynamic Analysis of Rhenium(I)–Formyl C–H Bond Formation via Base-Assisted Heterolytic H₂Cleavage in the Secondary Coordination Sphere

2013

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Conversion of synthesis gas, a mixture of carbon monoxide and hydrogen, into value-added C n≥2 products requires both C−H and C−C bond-forming events. Our group has developed a series of molecular complexes, based on group 7 (manganese and rhenium) carbonyl complexes, to interrogate the elementary steps involved in the homogeneous hydrogenative reductive coupling of CO. Here, we explore a new mode of H 2 activation, in which strong bases in the secondary coordination sphere are positioned to assist in the heterolytic cleavage of H 2 to form a formyl C−H bond at a rhenium-bound carbonyl. A series of cationic rhenium(I) complexes of the type [Re I (P∼B:-κ 1 -P)(CO) 5 ] n (n = 0, +1), where P∼B: is a phosphine ligand with a tethered strong base, are prepared and characterized; measurement of their protonation equilibria demonstrates a pronounced attenuation of the basicity upon coordination. Formyl complexes supported by these ligands can be prepared in good yield by hydride delivery to the parent pentacarbonyl complexes, and several of the free-base formyl complexes can be protonated, generating observable [Re I (P∼BH-κ 1 -P)(CHO)(CO) 4 ] n complexes. Intramolecular hydrogen bonding is evident for one of the complexes, providing additional stabilization to the protonated formyl complex. By measuring both the hydricity of the formyl, ΔG°H − , and its pK a , the overall free energy of H 2 cleavage is calculated from an appropriate cycle and found to be thermodynamically uphill in all cases (in the best case by only about 8 kcal/mol), although significantly dependent upon the properties of the supporting ligand.

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First Insertion Reaction of Carbon Monoxide into a Rhenium‐Carbon σ‐Bond

Abstract: Activation of the CO ligands in the new six‐membered rhenacycle (1), R = Ph, by AlBr3 permitted the first insertion of CO into a RhC σ‐bond. The complex (2) takes up CO at 20°C at normal pressure.

Cited by 18 publications

References 5 publications

Homogeneous CO Hydrogenation: Ligand Effects on the Lewis Acid-Assisted Reductive Coupling of Carbon Monoxide

Homogeneous CO Hydrogenation: Ligand Effects on the Lewis Acid-Assisted Reductive Coupling of Carbon Monoxide

Technetium and Rhenium

A Thermodynamic Analysis of Rhenium(I)–Formyl C–H Bond Formation via Base-Assisted Heterolytic H₂Cleavage in the Secondary Coordination Sphere

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First Insertion Reaction of Carbon Monoxide into a Rhenium‐Carbon σ‐Bond

Abstract: Activation of the CO ligands in the new six‐membered rhenacycle (1), R = Ph, by AlBr3 permitted the first insertion of CO into a RhC σ‐bond. The complex (2) takes up CO at 20°C at normal pressure.

Cited by 18 publications

References 5 publications

Homogeneous CO Hydrogenation: Ligand Effects on the Lewis Acid-Assisted Reductive Coupling of Carbon Monoxide

Homogeneous CO Hydrogenation: Ligand Effects on the Lewis Acid-Assisted Reductive Coupling of Carbon Monoxide

Technetium and Rhenium

A Thermodynamic Analysis of Rhenium(I)–Formyl C–H Bond Formation via Base-Assisted Heterolytic H2Cleavage in the Secondary Coordination Sphere

Contact Info

Product

Resources

About

A Thermodynamic Analysis of Rhenium(I)–Formyl C–H Bond Formation via Base-Assisted Heterolytic H₂Cleavage in the Secondary Coordination Sphere