- Self-assembly of para-OH functionalized ECE-metalated pincer complexes
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Various para-OH functionalized ECE-pincer metal complexes [MX(ECE-OH)Ln] (ECE-OH = [C6H2(CH2E)2-2,6-OH-4]-, E = NMe2, PPh2 and SPh) were synthesized. The X-ray crystal structures of neutral [PdCl(SCS-OH)], [PdCl(NCN-OH)], and cationic [Pd(PCP-OH)(MeCN)](BF4) are reported. The neutral halide complexes exhibit self-assembly to form polymeric chains via H-bonding involving the para-OH group as donors and the halide ligand on the metal as acceptors. Moreover, the halide ligand can be replaced by a monomeric aryloxy-O ligand leading to the formation of a covalently bonded dimer. The crystal structure of such a dimer derived from [PdI(NCN-OH)] is reported. Furthermore, these pincer-metal complexes were tethered through a carbamate linker to a siloxane functionality with the aim to be immobilized on a silica support. The crystal structure of a siloxane-functionalized [PtI(NCN-Z)] complex exemplifies how other H-bonding interactions not involving the metal-halide groupings can lead to polymeric networks as well.
- Mehendale, Nilesh C.,Lutz, Martin,Spek, Anthony L.,Klein Gebbink, Robertus J.M.,van Koten, Gerard
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p. 2971 - 2981
(2008/12/22)
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- Silica and polymer-tethered Pd-SCS-pincer complexes: Evidence for precatalyst decomposition to form soluble catalytic species in Mizoroki-Heck chemistry
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Palladium(II)-SCS-pincer complexes have been covalently immobilized on porous silica and polynorbornene supports and evaluated in the Mizoroki-Heck reaction of iodobenzene and n-butyl acrylate. Kinetic experiments and poisoning studies indicate that the pincer complexes decompose under reaction conditions via rupture of the palladium-ligand bonds to liberate active Pd(0) homogeneous species. There is no evidence for catalysis by the intact Pd(II) pincer complex under any conditions evaluated, ruling out a Pd(II)-Pd(IV) catalytic mechanism that has been postulated for palladacycle catalysts under the conditions used here.
- Yu, Kunquan,Sommer, William,Weck, Marcus,Jones, Christopher W.
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p. 101 - 110
(2007/10/03)
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