A Neutral Three-Coordinate Alkylrhodium(I) Complex: Stabilization of a 14-Electron Species byγ-C−H Agostic Interactions with a Saturated Hydrocarbon Group

Urtel, Heiko; Meier, Ch.; Eisenträger, Frank; Röminger, Frank; Joschek, Jens P.; Hofmann, Peter

doi:10.1002/1521-3757(20010216)113:4<803::aid-ange8030>3.0.co;2-o

Cited by 30 publications

(7 citation statements)

References 41 publications

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“…Intermediate B is a Rh I 14‐electron complex, which is expected to be unstable. Examples of isolated monovalent rhodium 14‐electron complexes are scarce 4c, 12. Having a methyl group in the β ‐position, B can easily undergo β ‐hydrogen elimination to give the rhodium( I ) 16‐electron methylene arenium compound 5 .…”

Section: Resultsmentioning

confidence: 99%

“…Of special interest are d 6 and d 8 14‐electron metal complexes, which are postulated as intermediates in various metal‐mediated processes, such as carbon–carbon9 and carbon–hydrogen10, 11 bond activation and functionalization. Formally 14‐electron d 6 iridium,4a ruthenium,3, 4b and d 8 rhodium4c, 12 complexes were reported. Also, examples of unsaturated platinum d 6 compounds are known 13.…”

Section: Introductionmentioning

confidence: 99%

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Interplay between Solvent and Counteranion Stabilization of Highly Unsaturated Rhodium(III) Complexes: Facile Unsaturation‐Induced Dearomatization

Gandelman

Konstantinovski

Rozenberg

et al. 2003

Chemistry A European J

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Abstraction of the chloride ligand from the PCN-based chloromethylrhodium complex 2 by AgX (X=BF(4)(-), CF(3)SO(3)(-)) or a direct C-C cleavage reaction of the PCN ligand 1 with [(coe)(2)Rh(solv)(n)](+)X(-) (coe=cyclooctene) lead to the formation of the coordinatively unsaturated rhodium(III) complexes 3. Compound 3 a (X=BF(4)(-)) exhibits a unique medium effect; the metal center is stabilized by reversible coordination of the bulky counteranion or solvent as a function of temperature. Reaction of [(PCN)Rh(CH(3))(Cl)] with AgBAr(f) in diethyl ether leads to an apparent rhodium(III) 14-electron complex 4, which is stabilized by reversible, weak coordination of a solvent molecule. This complex coordinates donors as weak as diethyl ether and dichloromethane. Upon substitution of the BF(4)(-) ion in [(PCN)Rh(CH(3))]BF(4) by the noncoordinating BAr(f)(-) ion in a noncoordinating medium, the resulting highly unsaturated intermediate undergoes a 1,2-metal-to-carbon methyl shift, followed by beta-hydrogen elimination, leading to the Rh-stabilized methylene arenium complex 5. This process represents a unique mild, dearomatization of the aromatic system induced by unsaturation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interplay between Solvent and Counteranion Stabilization of Highly Unsaturated Rhodium(III) Complexes: Facile Unsaturation‐Induced Dearomatization

Gandelman

Konstantinovski

Rozenberg

et al. 2003

Chemistry A European J

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“…Although other neutral T-shaped formally 14-electron Rh I complexes have been isolated, they are still very rare, and none of them have a halogen that can act as a bridging ligand. [80] CAAC 2 has also been used to prepare the cationic 14electron palladium complex [Pd(allyl)(CAAC 2 )]BF 4 by simple treatment of the corresponding palladium chloride with AgBF 4 . As expected, this complex features a T-shaped geometry ( Figure 5, left) with no interaction between the metal center and the tetrafluoroborate anion.…”

Section: Ligand Behaviormentioning

confidence: 99%

Stable Cyclic Carbenes and Related Species beyond Diaminocarbenes

2010

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The success of homogeneous catalysis can be attributed largely to the development of a diverse range of ligand frameworks that have been used to tune the behavior of various systems. Spectacular results in this area have been achieved using cyclic diaminocarbenes (NHCs) as a result of their strong σ-donor properties. Although it is possible to cursorily tune the structure of NHCs, any diversity is still far from matching their phosphorus-based counterparts, which is one of the great strengths of the latter. A variety of stable acyclic carbenes are known, but they are either reluctant to bind metals or they give rise to fragile metal complexes. During the last five years, new types of stable cyclic carbenes, as well as related carbon-based ligands (which are not NHCs), and which feature even stronger σ-donor properties have been developed. Their synthesis and characterization as well as the stability, electronic properties, coordination behavior, and catalytic activity of the ensuing complexes are discussed, and comparisons with their NHC cousins are made.

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“…[17] Similar agostic coordinations have been found for related isoelectronic complexes of Ni II , [19] Pt II , [20][21][22] and Rh I . [23,24] Strictly speaking, counting the agostic coordination, these complexes are tetracoordinated. However, the related complexes [PdArXL] (Ar = C 6 H 4 -OMe-p; X= NAr' 2 , Ar' = 3,5-(CF 3 ) 2 C 6 H 3 ; L= PtBu 3 , FcPtBu 2 , (Ph 5 Fc)PtBu 2 ; Fc = ferrocenyl), also reported by Yamashita and Hartwig, do not present agostic interactions and are unambiguously true tricoordinated complexes, the only ones reported so far for Pd II .…”

Section: Introductionmentioning

confidence: 99%

When Are Tricoordinated Pd^IISpecies Accessible? Stability Trends and Mechanistic Consequences

Moncho

Ujaque

Lledós

et al. 2008

Chemistry A European J

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The ease of access to Pd(II) tricoordinated species (whether intermediates or transition states) in organometallic and catalytic reactions has been assessed with DFT methods to analyze the relative stability of tricoordinated [PdArXL] complexes versus their tetracoordinated derivatives formed by two most common processes of filling the fourth coordination site: solvent coordination (with tetrahydrofuran), or dimerization to give [Pd2Ar2(micro-X)2L2]. The effect of each ligand (L=PH3, PMe3, PPh3, PtBu3, 1-AdPtBu2; Ar=C6F5, C6H5, C6H4OH, C6H4OCH3, C6H4NH2, C6H2(NH2)3; X=F, Cl, Br, I, OH, SH, NH2, PH2, CH3) on these two processes has been systematically considered, and the results have been compared with the experimental information available. The trends observed, match the experimental results and suggest that: 1) the formation of bridged dimeric complexes is strongly preferred; 2) electronic effects are in general less important compared to steric effects; 3) when steric effects prevent formation of bridges and coordination of a fourth external ligand, intramolecular agostic interactions are established with C--H groups of one ligand; 4) as an exception, for X=NR2 true tricoordinated complexes, not showing agostic interactions, become stable. In the later case NR2 seems to act as pi-donor with its lone pair to the empty orbital at the fourth coordination site of palladium, thus avoiding a true 14e configuration for the tricoordinated PdII complex.

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A Neutral Three-Coordinate Alkylrhodium(I) Complex: Stabilization of a 14-Electron Species byγ-C−H Agostic Interactions with a Saturated Hydrocarbon Group

Abstract: Selective activation and functionalization of alkanes by transition metals is a highly attractive goal [1] which has led to considerable efforts to understand hydrocarbon interactions

Cited by 30 publications

References 41 publications

Interplay between Solvent and Counteranion Stabilization of Highly Unsaturated Rhodium(III) Complexes: Facile Unsaturation‐Induced Dearomatization

Interplay between Solvent and Counteranion Stabilization of Highly Unsaturated Rhodium(III) Complexes: Facile Unsaturation‐Induced Dearomatization

Stable Cyclic Carbenes and Related Species beyond Diaminocarbenes

When Are Tricoordinated Pd^IISpecies Accessible? Stability Trends and Mechanistic Consequences

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A Neutral Three-Coordinate Alkylrhodium(I) Complex: Stabilization of a 14-Electron Species byγ-C−H Agostic Interactions with a Saturated Hydrocarbon Group

Abstract: Selective activation and functionalization of alkanes by transition metals is a highly attractive goal [1] which has led to considerable efforts to understand hydrocarbon interactions

Cited by 30 publications

References 41 publications

Interplay between Solvent and Counteranion Stabilization of Highly Unsaturated Rhodium(III) Complexes: Facile Unsaturation‐Induced Dearomatization

Interplay between Solvent and Counteranion Stabilization of Highly Unsaturated Rhodium(III) Complexes: Facile Unsaturation‐Induced Dearomatization

Stable Cyclic Carbenes and Related Species beyond Diaminocarbenes

When Are Tricoordinated PdIISpecies Accessible? Stability Trends and Mechanistic Consequences

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When Are Tricoordinated Pd^IISpecies Accessible? Stability Trends and Mechanistic Consequences