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@ARTICLE{Kleij:26930,
      author       = {Kleij, A. W. and Gossage, R. A. and Klein Gebbink, R. J. M.
                      and Brinkmann, N. and Reijerse, E. J. and Kragl, U. and
                      Lutz, M. and Spek, A. L. and van Koten, G.},
      title        = {{A} 'dendritic effect' in homogeneous catalysis with
                      carbosilane-supported arylnickel({II}) catalysts :
                      observation of active-site proximity effects in
                      atom-transfer radical addition},
      journal      = {Journal of the American Chemical Society},
      volume       = {122},
      issn         = {0002-7863},
      address      = {Washington, DC},
      publisher    = {American Chemical Society},
      reportid     = {PreJuSER-26930},
      pages        = {12112 - 12124},
      year         = {2000},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {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.},
      keywords     = {J (WoSType)},
      cin          = {IBT},
      ddc          = {540},
      cid          = {I:(DE-Juel1)VDB184},
      pnm          = {Verfahrenstechnik der Gewinnung},
      pid          = {G:(DE-Juel1)FUEK94},
      shelfmark    = {Chemistry, Multidisciplinary},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000165866400006},
      doi          = {10.1021/ja0026612},
      url          = {https://juser.fz-juelich.de/record/26930},
}