This title appears in the Scientific Report :
2000
Please use the identifier:
http://dx.doi.org/10.1021/ja0026612 in citations.
Please use the identifier: http://hdl.handle.net/2128/721 in citations.
A 'dendritic effect' in homogeneous catalysis with carbosilane-supported arylnickel(II) catalysts : observation of active-site proximity effects in atom-transfer radical addition
A 'dendritic effect' in homogeneous catalysis with carbosilane-supported arylnickel(II) catalysts : observation of active-site proximity effects in atom-transfer radical addition
Transmetalation of polylithiated, carbosilane (CS) dendrimers functionalized with the potentially terdentate ligand [C6H2(CH2NMe2)(2)-2,6-R-4](-) ( NCN) with NiCl2(PEt3)(2) produced a series of nickel-containing dendrimers [GO]-N-4 (4), [G1]-Ni-12 (5), and [G2]-Ni-36 (7) in moderate to good yields....
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Personal Name(s): | Kleij, A. W. |
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Gossage, R. A. / Klein Gebbink, R. J. M. / Brinkmann, N. / Reijerse, E. J. / Kragl, U. / Lutz, M. / Spek, A. L. / van Koten, G. | |
Contributing Institute: |
Institut für Biotechnologie; IBT |
Published in: | Journal of the American Chemical Society, 122 (2000) S. 12112 - 12124 |
Imprint: |
Washington, DC
American Chemical Society
2000
|
Physical Description: |
12112 - 12124 |
DOI: |
10.1021/ja0026612 |
Document Type: |
Journal Article |
Research Program: |
Verfahrenstechnik der Gewinnung |
Series Title: |
Journal of the American Chemical Society
122 |
Subject (ZB): | |
Link: |
OpenAccess |
Publikationsportal JuSER |
Please use the identifier: http://hdl.handle.net/2128/721 in citations.
Transmetalation of polylithiated, carbosilane (CS) dendrimers functionalized with the potentially terdentate ligand [C6H2(CH2NMe2)(2)-2,6-R-4](-) ( NCN) with NiCl2(PEt3)(2) produced a series of nickel-containing dendrimers [GO]-N-4 (4), [G1]-Ni-12 (5), and [G2]-Ni-36 (7) in moderate to good yields. The metallodendrimers 4, 5, and 7 are catalytically active in the atom-transfer radical addition (ATRA) reaction (Kharasch addition reaction), viz. the 1:1 addition of CCl4 to methyl methacrylate (MMA). The catalytic data were compared to those obtained for the respective mononuclear compound [NiCl(C6H2{CH2NMe2}(2)-2,6-SiMe3-4)] (2). This comparison indicates a fast deactivation for the dendrimer catalysts beyond generation [GO]. The deactivation of [G1]-Ni-12 (5) and [G2]-Ni-36 (7) is caused by irreversible formation of catalytically inactive Ni(III) sites on the periphery of these dendrimers. This hypothesis is supported by results of model studies as well as ESR spectroscopic investigations. Interestingly, the use of two alternative nickelated [G1] dendrimers [G1]*-Ni-12 (11) and [G1]-Ni-8 (15), respectively, in which the distance between the Ni sites is increased, leads to significantly improved catalytic efficiencies which approximate those of the parent derivative 2 and [GO]-Ni-4 (4). Preliminary membrane catalysis experiments with [GO]-Ni-4 (4) and [G1]-Ni-12 (5) show that 5 can be efficiently retained in a membrane reactor system. The X-ray crystal structure of the Ni(III) complex [NiCl2(C6H2{CH2NMe2}(2)-2,6-SiMe3-4)] (16), obtained from the reaction of 2 with CCl4, is also reported. |