Organometallic chemistry of fluorinated propadienes and butadienes

Lentz, Dieter

doi:10.1016/j.jfluchem.2004.02.018

Cited by 21 publications

(5 citation statements)

References 89 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the 1 H NMR spectrum, the dppm CH 2 protons appear at δ 4.79 and 4.46, while the CH 2 protons of the fluoroallene ligand appear as a triplet at δ 1.55, coupling to the 31 P nuclei at δ −12.0 ( 3 J HP = 11.8 Hz). The observation of one allene CH 2 resonance is consistent with binding through this end of the cumulene, as is typically observed. ,,, The upfield chemical shift of the CH 2 protons also suggests that they are adjacent to Os and not Ir, the latter of which characteristically resonate downfield at ca. δ 4.…”

Section: Results and Compound Characterizationsupporting

confidence: 76%

“…Rearrangement of the bridging difluoroallene to a μ-η 3 :κ 1 hydrocarbyl fragment, as observed with allene and methylallene, is never observed, with the κ 1 :κ 1 -difluoroallene arrangement being retained upon heating to 40 °C for 8 h, after which time, decomposition occurs. The η 3 -allyl binding mode has previously been reported for 1,1-difluoroallene in only two multimetallic systems. ,, …”

Section: Results and Compound Characterizationmentioning

confidence: 85%

See 1 more Smart Citation

Diverse Coordination Modes and Transformations of Allenes at Adjacent Iridium/Osmium Centers

et al. 2012

View full text Add to dashboard Cite

The methylene-bridged complex, [IrOs(CO) 3 (μ-CH 2 )(dppm) 2 ][BF 4 ] (dppm = μ-Ph 2 PCH 2 PPh 2 ) (2), reacts with allene, resulting in C−C bond formation, to yield an equilibrium mix of two isomers of [IrOs(CO) 3 (μ-η 3 :κ 1 -C(CH 2 ) 3 )(dppm) 2 ][BF 4 ] (3/3a), in which the hapticity of the trimethylenemethane ligand with respect to the two metals, as well as the carbonyl ligand arrangement, is different in each isomer. Reaction of 2, as the triflate salt (2-CF 3 SO 3 ), with methylallene also yields two isomers, [IrOs(CO) 3 (μ-η 3 :κ 1 -C(CHCH 3 )(CH 2 ) 2 )(dppm) 2 ][CF 3 SO 3 ] (4/4a); however, in this case, the binding mode of the substituted trimethylenemethane moiety is the same in each isomer and differs only in the position of the methyl group on the allylic moiety. The addition of 1,1-dimethylallene to 2-CF 3 SO 3 results in loss of 4-methyl-1,3pentadiene and subsequent reaction of the remaining "[IrOs(CO) 3 (dppm) 2 ] + " species with excess 1,1-dimethylallene to give [IrOs(CO) 3 (μ-η 3 :κ 1 -CH 2 CCMe 2 )(dppm) 2 ][CF 3 SO 3 ] (5), in which the dimethylallene moiety is κ 1 -bound to Os through the central carbon and η 3 -bound to Ir. Both allene and methylallene react with the tetracarbonyl complex, [IrOs(CO) 4 (dppm) 2 ]-[BF 4 ] (6), to generate analogous products, [IrOs(CO) 3 (μ-η 3 :κ 1 -CH 2 CCHR)(dppm) 2 ][BF 4 ] (R = H (7), CH 3 (8), respectively). Reaction of 6-CF 3 SO 3 with 1,1-dimethylallene yields [IrOs(CO) 4 (μ-CC(H)C(CH 3 )CH 2 )(dppm) 2 ][CF 3 SO 3 ] (9), the result of activation of the geminal C−H bonds of the unsubstituted end of the allene, and additional activation of a methyl C−H bond. The addition of 1,1-difluoroallene to 6-CF 3 SO 3 yields [IrOs(CO) 4 (μ-κ 1 :κ 1 -F 2 CCCH 2 )(dppm) 2 ][CF 3 SO 3 ] (10), in which this cumulene bridges both metal centers through the central carbon and the CH 2 end of the substrate. These reactivities are compared to those of related Ir 2 , Rh/Ru, Rh/Os, and Ir/Ru complexes.

show abstract

Section: Results and Compound Characterizationsupporting

confidence: 76%

Section: Results and Compound Characterizationmentioning

confidence: 85%

Diverse Coordination Modes and Transformations of Allenes at Adjacent Iridium/Osmium Centers

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Binding of the 1,1-difluoroallene ligand through the “CCH 2 ” end is further supported by the appearance of two resonances in the 19 F NMR spectrum for both 5 and 5a , demonstrating their chemical inequivalence as diagrammed in Scheme . The mutual two-bond coupling between these fluorines (58.6 Hz ( 5 ) and 66.5 Hz ( 5a )) is typical. , Binding of 1,1-difluoroallene through the hydrogen-substituted double bond is its typical binding mode. , …”

Section: Results and Compound Characterizationmentioning

confidence: 99%

Geminal Carbon–Hydrogen Bond Activation in Cumulenes Promoted by Adjacent Iridium/Ruthenium Centers

et al. 2012

View full text Add to dashboard Cite

The tetracarbonyl complex [IrRu(CO) 4 (dppm) 2 ][BF 4 ] (dppm = μ-Ph 2 PCH 2 PPh 2 ) (1) reacts with allene and methylallene, resulting in double, geminal carbon−hydrogen bond activation accompanied by H migration, one each to the βand γ-carbons of the allene, yielding the vinylidene-bridged complexes [IrRu(CO) Reaction of 1 with 1,1-dimethylallene results in the activation of the pair of geminal C−H bonds together with one of the methyl C−H bonds, yielding the vinylvinylidene-bridged product [IrRu(CO) 4 4), accompanied by H 2 loss. The addition of 1,1-difluoroallene to compound 1 does not lead to C−H activation but instead forms the fluoroallene-bridged adduct [IrRu(CO) 4 (μ-κ 5), bound through the unsubstituted end of the allene and having the CH 2 group bound to Ru. This species rearranges, over 24 h at ambient temperature, to its isomer (5a), having the CH 2 end bound to Ir. Although ethylene and propylene fail to react with 1 at ambient temperature, they react with the tricarbonyl analogue [IrRu(CO) 3 ( dppm) 2 ][BF 4 ] (8) at −20 °C to yield the alkenyl-bridged hydrides [IrRu(CO) 3 (H)(μ-κ 1 :η 2 -C(H)CHR)(dppm) 2 ][BF 4 ] (R = H (6), CH 3 (7)), by activation of a single C−H bond. Compound 8 reacts similarly with allene at −20 °C, yielding [IrRu(H)(CO) 3 (μ-κ 1 :η 2 -CH CCH 2 )(dppm) 2 ][BF 4 ] (11). None of these alkenyl or allenyl hydride species give rise to a second C−H activation upon warming. However, warming 11 in the presence of CO does yield 2, together with decomposition products. Removal of a carbonyl from the vinylidene-bridged complexes [IrRu(CO) 4 (μ-CC(H)R)(dppm) 2 ][BF 4 ] (R = CH 3 (2), R = H (9)) generates the alkynyl hydride complexes [IrRu(H)(CO) 3 (μ-κ 1 :η 2 -CCR)(dppm) 2 ][BF 4 ] (R = CH 3 ( 12), H (10)), both of which can be converted back to the respective vinylidenes by CO addition. On the basis of these observations, a mechanism is proposed for the transformations of allene and methylallene into the methyl-and ethylvinylidene-bridged products, noted above.

show abstract

“…The thermodynamic stability of C–F bonds [bond dissociation energy (BDE) = 110–130 kcal mol –1 ], combined with their inherent kinetic inertness, has allowed for many technical applications of fluorocarbons in medicinal chemistry as well as the synthesis of resistant polymers. − However, such strong bonding is also troublesome in view of the fact that these chemically inert compounds are persistent in the environment. , Therefore, in recent years, synthetic methods for the activation and functionalization of C–F bonds have attracted growing attention. ,,− With increasing degree of fluorination at carbon, the C–F bond strength increases and the C–F bond length decreases, resulting in substantial steric shielding of the carbon site . Because of this increased stability, fluorine abstraction from a CF 3 moiety is difficult and rare. ,,,− …”

mentioning

confidence: 99%

Dis-assembly of a Benzylic CF₃ Group Mediated by a Niobium(III) Imido Complex

2013

View full text Add to dashboard Cite

show abstract

Organometallic chemistry of fluorinated propadienes and butadienes

Cited by 21 publications

References 89 publications

Diverse Coordination Modes and Transformations of Allenes at Adjacent Iridium/Osmium Centers

Diverse Coordination Modes and Transformations of Allenes at Adjacent Iridium/Osmium Centers

Geminal Carbon–Hydrogen Bond Activation in Cumulenes Promoted by Adjacent Iridium/Ruthenium Centers

Dis-assembly of a Benzylic CF₃ Group Mediated by a Niobium(III) Imido Complex

Contact Info

Product

Resources

About

Organometallic chemistry of fluorinated propadienes and butadienes

Cited by 21 publications

References 89 publications

Diverse Coordination Modes and Transformations of Allenes at Adjacent Iridium/Osmium Centers

Diverse Coordination Modes and Transformations of Allenes at Adjacent Iridium/Osmium Centers

Geminal Carbon–Hydrogen Bond Activation in Cumulenes Promoted by Adjacent Iridium/Ruthenium Centers

Dis-assembly of a Benzylic CF3 Group Mediated by a Niobium(III) Imido Complex

Contact Info

Product

Resources

About

Dis-assembly of a Benzylic CF₃ Group Mediated by a Niobium(III) Imido Complex