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

H.P. Dijkstra, C.A. Kruithof, N.J. Ronde, R. Coevering, van de, D.J. Ramon, D. Vogt, G.P.M. Klink, van, G. Koten, van

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    Abstract

    Shape-persistent multi(NCN-Pd and/or -Pt) complexes having one- (p-C6H4(C6H2(CH2NMe2)2-3,5-PtI-4)2 (5) and BrPt(C6H3(CH2NMe2)2-2,6) (6)), two- (C6H3(C6H2(CH2NMe2)2-3,5-PtBr-4)3-1,3,5 (1c; prepn. previously published)) and C6H3(C6H4(C6H2(CH2NMe2)2-3,5-ML-4)-4)3-1,3,5 (2a-c; ML = PdBr, Pd(OH2)(BF4), PtBr), and three-dimensional (Si(C6H3(CH2OC6H2(CH2NMe2)2-3,5-ML-4)2-3,5)4 (3a-c; ML = PdI, Pd(OH2)(BF4), PtI)) and C6(C6H3(CH2OC6H2(CH2NMe2)2-3,5-ML-4)2-3,5)6 (4a-c; ML = PdI, Pd(OH2)(BF4), PtBr) geometries were prepd. 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 1-pot coupling of monometallic building blocks to a multifunctional shape-persistent org. core mol. The 1st approach was used to prep. the palladated and/or platinated tris- (2) and bis(NCN-pincer) (5) complexes, while the 2nd approach afforded the palladated and platinated octakis- (3) and dodecakis(NCN-pincer) (4) complexes. Complexes 1-6 were subjected to nanofiltration (NF) expts. to study the influence of rigidity and geometry on the retention of these mols. 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 SO2 in soln. gave bright orange complexes, allowing the use of UV/visible spectroscopy to accurately det. the concns. 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%, resp. A clear relation is obsd. between the dimensions calcd. by mol. modeling and the retention rates of 1-6. The 1-dimensional bis(pincer-Pt) complex 5, however, shows an unexpectedly high retention rate (99.6%) that can be due to pptn. of the complex in the membrane (clogging of the membrane) and/or to the formation of larger aggregates near the membrane. In addn., 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 macromol. complexes indeed leads to more efficient retentions of these multimetallic materials by NF-membranes
    Original languageEnglish
    Pages (from-to)675-685
    JournalJournal of Organic Chemistry
    Volume68
    Issue number3
    DOIs
    Publication statusPublished - 2003

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