Toward Metal-Stabilized Silylium Cations: An EHMO Study of [(HC.tplbond.C-SiH2)Co2(CO)6]+ and X-ray Crystal Structures of (Me3SiC.tplbond.CSiPh2H)Mo2(CO)4Cp2 and [(Me3SiC.tplbond.CSiMe2)Co2(CO)6]2O

Ruffolo, Ralph; Decken, Andreas; Girard, Luc; Gupta, Hari K.; Brook, Michael A.; McGlinchey, Michael J.

doi:10.1021/om00023a041

Cited by 20 publications

(12 citation statements)

References 5 publications

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“…The former were potentially preparable by elimination of propene from an allyl-silane, [19] while the latter could be generated through protonation of an alcohol or an alkene, as shown in Scheme 4. In the case of 7 a (R = Me), the observed outcome of the experiment involved initial formation of the carbocation 8 a, which underwent intramolecular nucleophilic attack by the terminus of the allyl group thus furnishing the b-silyl cation 9 a.…”

Section: Resultsmentioning

confidence: 99%

Solvent‐Mediated Generation of Cobalt‐Cluster‐Stabilised Propargyl Cations and Radicals: Allyl Migration versus Peroxide Formation

Kaldis

Brook

McGlinchey

2008

Chemistry A European J

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The protonation of [Co(2)(CO)(6){9-[(allyldimethylsilyl)ethynyl]-9H-fluoren-9-ol}] (4), with HBF(4) in CH(2)Cl(2) led to migration of the allyl group from silicon to the cobalt-stabilised cationic site to furnish [Co(2)(CO)(6){9-allyl-9-[(dimethylfluorosilyl)ethynyl]-9H-fluorene}] (17). However, under the same conditions, [Co(2)(CO)(6){9-[(benzyldimethylsilyl)ethynyl]-9H-fluoren-9-ol}] (5) underwent desilylation and rearrangement of the resulting terminal alkyne-dicobalt complex to give [Co(3)(CO)(9)(9H-fluorenylmethylcarbynyl)] (24); moreover, dimerisation of the (benzyldimethylsilyl)ethynyl-9H-fluorenyl moiety led to the propargyl-allene 26. In contrast, protonation of 5 in THF yielded [{Co(2)(CO)(6){[(benzyldimethylsilyl)ethynyl-9H-fluorenyl])}(2)peroxide] (27) through a radical coupling process. Analogously, protonation of [Co(2)(CO)(6){9-[(vinyldimethylsilyl)ethynyl]-9H-fluoren-9-ol}] (6) yields the corresponding peroxide 28. X-ray crystallographic data are reported for, among others, complexes 17, 24, 26, 27 and 28.

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Section: Resultsmentioning

confidence: 99%

Solvent‐Mediated Generation of Cobalt‐Cluster‐Stabilised Propargyl Cations and Radicals: Allyl Migration versus Peroxide Formation

Kaldis

Brook

McGlinchey

2008

Chemistry A European J

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“…Reactivity enhancement of metal coordinated halo- and hydrosilylalkynes is a well-documented fact [10,11,14,15,16]. In a previous study, we have shown that oligosilanylalkyne coordination to the dicobalthexacarbonyl fragment results in the formation of highly reactive compounds [17].…”

Section: Discussionmentioning

confidence: 99%

“…For the silicon case, silylium ions are likely to be involved in reactions of the respective complexes, as was demonstrated by Corriu and co-workers, who reacted their dicobalthexacarbonyl coordinated hydrosilylalkyne with Ph 3 C[BF 4 ] to obtain the respective dicobalthexacarbonyl complexed fluorosilane [11]. Theoretical and experimental aspects of the formation of transition metal-stabilized silylium ions were further studied by Brook and co-workers using again dicobalt- but also dimolybdenum-complexes for the coordination of silylated alkynes [14,15,16].…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic and Structural Study of Some Oligosilanylalkyne Complexes of Cobalt, Molybdenum and Nickel

2019

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Metal induced stabilization of α-carbocations is well known for cobalt- and molybdenum complexed propargyl cations. The same principle also allows access to reactivity enhancement of metal coordinated halo- and hydrosilylalkynes. In a previous study, we have shown that coordination of oligosilanylalkynes to the dicobalthexacarbonyl fragment induces striking reactivity to the oligosilanyl part. The current paper extends this set of oligosilanylalkyne complexes to a number of new dicobalthexacarbonyl complexes but also to 1,2-bis(cyclopentadienyl)tetracarbonyldimolybdenum and (dippe)Ni complexes. NMR-Spectroscopic and crystallographic analysis of the obtained complexes clearly show that the dimetallic cobalt and molybdenum complexes cause rehybridization of the alkyne carbon atoms to sp3, while in the nickel complexes one π-bond of the alkyne is retained. For the dicobalt and dimolybdenum complexes, strongly deshielded 29Si NMR resonances of the attached silicon atoms indicate enhanced reactivity, whereas the 29Si NMR shifts of the respective nickel complexes are similar to that of respective vinylsilanes.

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“…(4)) by the Co 2 (CO) 6 unit; migration barriers on indene and rates of allyl protonation show no sizeable differences from the metal free systems [22]. EHMO calculations suggest a modest stabilization is possible [23]. (CO) 6 Co 2 (Ph 3 P)(CO) 5 Co 2 (Ph 3 P)(CO) 5 Co 2 (CO) 6 Co 2 Fig.…”

Section: Fundamental Propertiesmentioning

confidence: 99%

“…The source of attention stems the instability of The Green group has demonstrated that the suitably constructed allylsilanes (21), derived themselves from intermolecular Nicholas reactions with silylated allylstannanes (22) [24] undergo 7-endo trig cyclization to afford cycloheptenyne complexes (23) in excellent yield (Scheme 8) [47]. A version of this cyclization may also afford exo methylene complexes.…”

Section: Cycloalkyne Ring Forming Reactionsmentioning

confidence: 99%

Chemistry of Propargyldicobalt Cations Recent Developments in the Nicholas and Related Reactions

Green

2001

COC

145

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Abstract:The chemistry of propargyldicobalt cations, also known as the Nicholas reaction, is reviewed, with a focus on the developments since 1995. Advances in the understanding of the fundamental properties, such as structure, stability, and reactivity, of both the hexacarbonyl complexes and those bearing other ligands are discussed. All reactions involving propargyl cation dicobalt complexes are covered, including those stemming from ionization of propargylic leaving groups and those created by electrophilic addition to enyne complexes. Migration reactions involving either initiation or termination by propargyl cation complexes are included, as are the generation and reactions of propargyldicobalt radicals. Cyclization reactions employing these cations have received much attention, in cases with the alkynedicobalt unit located in both exocyclic and endocyclic positions, and these reports are described. Particular attention is paid to preparation of medium ring cycloalkyne complexes and their heterocyclic analogues. In addition, there is discussion of the progress in the in selectivity of these reactions, especially in terms of introduction of asymmetry at the propargylic site. Finally, recent applications of Nicholas reaction chemistry in the synthesis of natural products and related compounds are reported.

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Toward Metal-Stabilized Silylium Cations: An EHMO Study of [(HC.tplbond.C-SiH2)Co2(CO)6]+ and X-ray Crystal Structures of (Me3SiC.tplbond.CSiPh2H)Mo2(CO)4Cp2 and [(Me3SiC.tplbond.CSiMe2)Co2(CO)6]2O

Cited by 20 publications

References 5 publications

Solvent‐Mediated Generation of Cobalt‐Cluster‐Stabilised Propargyl Cations and Radicals: Allyl Migration versus Peroxide Formation

Solvent‐Mediated Generation of Cobalt‐Cluster‐Stabilised Propargyl Cations and Radicals: Allyl Migration versus Peroxide Formation

Spectroscopic and Structural Study of Some Oligosilanylalkyne Complexes of Cobalt, Molybdenum and Nickel

Chemistry of Propargyldicobalt Cations Recent Developments in the Nicholas and Related Reactions

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