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Inorganics 2016, 4(2), 8;

Hexacoordinate Silicon Compounds with a Dianionic Tetradentate (N,N′,N′,N)-Chelating Ligand

Institut für Anorganische Chemie, TU Bergakademie Freiberg, D-09596 Freiberg, Germany
Institut für Analytische Chemie, TU Bergakademie Freiberg, D-09596 Freiberg, Germany
Author to whom correspondence should be addressed.
Academic Editors: Duncan H. Gregory and Cameron Jones
Received: 17 March 2016 / Revised: 6 April 2016 / Accepted: 7 April 2016 / Published: 14 April 2016
(This article belongs to the Special Issue Traversing the Boundaries of Inorganic Chemistry)
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In the context of our systematic investigations of penta- and hexacoordinate silicon compounds, which included dianionic tri- (O,N,O′; O,N,N′) and tetradentate (O,N,N,O; O,N,N′,O′) chelators, we have now explored silicon coordination chemistry with a dianionic tetradentate (N,N′,N′,N) chelator. The ligand [o-phenylene-bis(pyrrole-2-carbaldimine), H2L] was obtained by condensation of o-phenylenediamine and pyrrole-2-carbaldehyde and subsequently silylated with chlorotrimethylsilane/triethylamine. Transsilylation of this ligand precursor (Me3Si)2L with chlorosilanes SiCl4, PhSiCl3, Ph2SiCl2, (Anis)2SiCl2 and (4-Me2N-C6H4)PhSiCl2 afforded the hexacoordinate Si complexes LSiCl2, LSiPhCl, LSiPh2, LSi(Anis)2 and LSiPh(4-Me2N-C6H4), respectively (Anis = anisyl = 4-methoxyphenyl). 29Si NMR spectroscopy and, for LSiPh2, LSi(Anis)2 and LSiPh(4-Me2N-C6H4), single-crystal X-ray diffraction confirm hexacoordination of the Si atoms. The molecular structures of LSiCl2 and LSiPhCl were elucidated by computational methods. Despite the two different N donor sites (pyrrole N, X-type donor; imine N, L-type donor), charge delocalization within the ligand backbone results in compounds with four similar Si–N bonds. Charge distribution within the whole molecules was analyzed by calculating the Natural Charges (NCs). Although these five compounds carry electronically different monodentate substituents, their constituents reveal rather narrow ranges of their charges (Si atoms: +2.10–+2.22; monodentate substituents: −0.54–−0.56; L2−: −1.02–−1.11). View Full-Text
Keywords: hypercoordination; imine; pyrrole; 29Si NMR spectroscopy; X-ray diffraction hypercoordination; imine; pyrrole; 29Si NMR spectroscopy; X-ray diffraction

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Gerlach, D.; Brendler, E.; Wagler, J. Hexacoordinate Silicon Compounds with a Dianionic Tetradentate (N,N′,N′,N)-Chelating Ligand. Inorganics 2016, 4, 8.

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