Phosphine-functionalized dendrimers for transition-metal catalysis

Reek, Joost N. H.; Groot, Debby de; Oosterom, G. Eric; Kamer, Paul C. J.; Leeuwen, Piet W. N. M. van

doi:10.1016/j.crci.2003.06.007

Cited by 44 publications

(8 citation statements)

References 52 publications

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“…The formation of these catalytically active species is favored in polar solvents, which could explain the higher conversions observed in DMF compared with less polar solvents such as scCO 2 or toluene. The divergent reactivity observed in DMF between the dendritic and nondendritic systems can be ascribed to the local apolar environment originating from the dendritic carbosilane shell or to the lower accessibility of the catalytic site located at the core of the dendrimer . The second explanation is in apparent contradiction with the behavior observed in toluene, where 3a shows comparable activity with respect to the PPh 3 complex, if the conformational flexibility of the dendritic wedges is not taken into account.…”

Section: Resultsmentioning

confidence: 84%

“…Metal catalysts can be coordinated to the surface of dendrimers or embedded in the dendritic framework. , Core-functionalized systems contain a large number of terminal groups per active site and are specially suited for these purposes. Several examples of mono- and diphosphine ligands located in the core of carbosilane dendrimers have been reported up to now. − …”

Section: Introductionmentioning

confidence: 99%

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Carbosilane Dendrons as Solubilizers of Metal Complexes in Supercritical Carbon Dioxide

et al. 2006

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Palladium complexes of general formula [PdCl2(L)2], 3a−c, were synthesized by reaction of [PdCl2(COD)] (COD = 1,5-cyclooctadiene) with the appropriate functionalized phosphine L = [P(C6H5) n ((C6H4CH2CH2Si(CH2CH2CH2SiEtMe2)3)3 - n )] (n = 2, 2a; 1, 2b; 0, 2c, respectively), which integrated carbosilane dendritic wedges attached to the para-carbon atom of the phenyl group. As a result of the inclusion of the carbosilane dendrons, the solubility of the corresponding palladium complexes 3 in supercritical carbon dioxide (scCO2) was increased in comparison with the palladium complex containing a PPh3 ligand, which showed negligible solubility. The employment of these complexes as precatalysts in a selected Heck coupling reaction in scCO2 was investigated. Good activities were found for 3a−c in such a medium due to the acquired solubility, in contrast with the palladium complex containing PPh3, which showed no activity.

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Section: Resultsmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Carbosilane Dendrons as Solubilizers of Metal Complexes in Supercritical Carbon Dioxide

et al. 2006

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“…Therefore, the reverse activity shown by monometallic versus dendritic catalysts in neat TBS and CH 2 Cl 2 is more likely to be caused by the different rates of the insertion steps than by catalyst degradation. It is well-known that adaptation of the dendritic conformation to the polarity of the solvent can lead to changes in the catalytic behavior . On the other hand, it is remarkable that activities seem to stabilize after 24 h, and their values are, 4 days later, about 10% of those registered during the first day.…”

Section: Resultsmentioning

confidence: 99%

Neutral and Cationic Dendritic Palladium(II) Complexes ContainingN,N‘-Iminopyridine Chelating Ligands. Synthesis and Their Use for the Syndiospecific Copolymerization of CO/4-tert-Butylstyrene

et al. 2006

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Series of neutral and cationic palladium carbosilane dendritic compounds of the general formula Gn-ONNMe2) or 16 (n ) 3) terminal pyridylimine complexes, substituted with m methyl groups (m ) 0, 2, 3), along with the corresponding monometallic counterparts (n ) 0), have been synthesized. Monometallic or dendritic chloro methyl or cationic methyl palladium compounds consist of a cis/trans mixture of diastereoisomers, with compositions according to their electronic and steric features. The cationic compounds Gn-ONNMe m [PdMe(MeCN)] + are found to be active catalysts for the alternating copolymerization of CO and 4-tert-butylstyrene, producing mainly syndiotactic polyketones due to a chain-end stereocontrolled mechanism. Modification of the pyridylimine ligand framework by methyl substituents has a decisive influence on the activities of the palladium compounds. Some of them are found to retain some activity after several days of catalytic reaction. Also, the size (i.e., generation n) of the dendritic precursor affects the catalyst performance and the microstructure of the copolymerization products. Thus, higher generation catalysts show superior activities and produce shorter and less stereoregular copolymer chains.

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“…Membrane filtration can also be achieved by attaching carbosilane dendrimers to a single bidentate ligand [113]. In this case, the ligand itself serves as core for the dendrimer, and the size and polarity can be tuned as desired.…”

Section: Dendrimers As Supports: Membrane Filtrationmentioning

confidence: 99%