Dieter Vogt

Publications (2)4.45 Total impact

• Source

  Available from: uu.nl

  Article: Shape-persistent nanosize organometallic complexes: synthesis and application in a nanofiltration membrane reactor.

  Harm P Dijkstra, Cornelis A Kruithof, Niek Ronde, Rob Van De Coevering, Diego J Ramón, Dieter Vogt, Gerard P M Van Klink, Gerard Van Koten
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  ABSTRACT: Shape-persistent multi(NCN-palladium and/or -platinum) complexes having one- (5 and 6), two- (1 and 2), and three-dimensional (3 and 4) geometries were prepared in moderate to good yields. Two different approaches were used to construct the multimetallic materials: (i) the construction of the multisite ligands followed by the permetalation step and (ii) selective and mild one-pot coupling of monometallic buiding blocks to a multifunctional shape-persistent organic core molecule. The first approach was used to prepare the palladated and/or platinated tris- (2) and bis(NCN-pincer) (5) complexes, while the second approach afforded the palladated and platinated octakis- (3) and dodecakis(NCN-pincer) (4) complexes. Complexes 1-6 were subjected to nanofiltration (NF) experiments in order to investigate the influence of rigidity and geometry on the retention of these molecules by NF membranes. For this purpose, the corresponding (NCN-Pt-X)(n)() complexes (1c-4c, 5, and 6) were used since exposing these complexes to sulfur dioxide in solution resulted in the formation of bright orange complexes, allowing the use of UV/vis spectroscopy to accurately determine the concentrations of 1-6 in both retentate and permeate. Using the MPF-60 (MWCO = 400) NF-membrane, retention rates of 82.4 (6), 93.9 (1c), 98.7 (2c), 99.5 (3c), 99.6 (5), and >99.9% (4c) were found, while 2c and 4c in combination with the MPF-50 (MWCO = 700) NF-membrane were retained in 97.6 and 99.9%, respectively. A clear relationship is observed between the dimensions calculated by molecular modeling and the retention rates of 1-6. The one-dimensional bis(pincer-platinum) complex 5, however, shows an unexpectedly high retention rate (99.6%) that can be due to precipitation of the complex in the membrane (clogging of the membrane) and/or to the formation of larger aggregates near the membrane. In addition, comparison of 2 and 4 with flexible nickelated G0- and G1-dendrimers with similar dimensions proved that a high degree of rigidity in the backbone of macromolecular complexes indeed leads to more efficient retentions of these multimetallic materials by NF-membranes.
  The Journal of Organic Chemistry 02/2003; 68(3):675-85. · 4.45 Impact Factor
• Article: Application of a Homogeneous Dodecakis(NCN-PdII) Catalyst in a Nanofiltration Membrane Reactor under Continuous Reaction Conditions

  Harm P. Dijkstra, Gerard P. M. van Klink, Dieter Vogt, Gerard van Kotena
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  ABSTRACT: A shape-persistent nanosize dodeca- kis(NCN-PdII-aqua) complex (4b) was applied as a homogeneous catalyst in the double Michael reaction between methyl vinyl ketone and ethyl -cyanoace- tate under continuous reaction conditions in a nano- filtration membrane reactor. Due to its macromolec- ular dimensions, the catalyst is retained in the reactor (R 99.5% determined by ICP-AAS) during cataly- sis. In addition, the catalyst was found to be stable under the continuous reaction conditions as a con- stant activity was obtained at prolonged reaction times (26 h, 65 exchanged reactor volumes). The turnover number of the catalyst was thus increased by a factor greater than 40 from 80 (batch) up to 3000 mol/mol Pd. Further development of this technology will allow an increase of the number of (industrial) catalytic processes in which homogeneous catalysts are applied.