Synthesis, coordination chemistry and reactivity of new diarylamido and disilylamido SeNSe pincer ligands
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Date
2015-11-10, 2016-06-09
Authors
Charette, Bronte J.
Journal Title
Journal ISSN
Volume Title
Publisher
Canadian Science Publishing
American Chemical Society Publications
American Chemical Society Publications
Abstract
This thesis presents advancements in the chemistry of selenium-bearing pincer ligands with respect to their synthesis, metal association and reactivity in addition to the overall nature of selenium as a donor atom.
The synthesis of a new disilylamido ligand HN(SiMe2CH2SePh)2 2.1 and its potassium salt 2.2 is reported. The attempted metal association of these species was unsuccessful with various transition metals. Multinuclear NMR data suggests coordination to silver(I), 2.3 and copper(I), 2.4 with dπ-dπ back donation from the metal to the selenium donors. It is suggested from this data that –SePh can potentially act as a π-acceptor ligand as well as a σ- donor with heavy d metals. Another explanation for the observed shielding is conformational restrictions introduced by chelation.
The preparation of new selenium-bearing diarylamine compounds RN(C7H6SeMe)2 (R=H: 3.1; R= Me: 3.10; R= Boc 3.11) via aryllithium chemistry is reported. Unsuccessful attempts to synthesize the –SePh and –SetBu derivatives are described using: aryllithium chemistry, Buchwald-Hartwig Amination cross coupling and Pd-catalyzed C-Se cross coupling. When reacted with MCl2(COD) (M= Pd, Pt), compound 3.10 coordinates with PdII forming a bidentate complex 3.12, while 3.1 forms tridentate complexes with PdII and PtII. NMR spectroscopy suggests the formation of a silver(I) complex 3.1-Ag from 3.1 and AgOTf, but X-ray diffraction data is required to determine its coordination motif. The new ligands and complexes have been fully characterized by (1H, 13C, 77Se) NMR spectroscopy and X-ray crystal structures are reported for 3.10, 3.12, 3.3 and 3.4. The NMR spectrum of 3.1-Ag exhibits a similar effect as the complexes of disilylamido ligands with suggested potential dπ-dπ back donation from the metal to the selenium donors.
The catalytic ability of the new complex 3.3 has been tested in the Suzuki-Miyaura cross coupling reaction without notable improvements to existing catalysts. The instability of reactive intermediates may contribute to the low conversions or the size of the methyl group may decrease nanoparticle formation, a suggested active species.
Description
Keywords
Inorganic chemistry, Organometallics, Ligand design, Coordination chemistry, Selenium donors
Citation
Canadian Journal of Chemistry, 2016, 94(4): 386-391
Inorg. Chem., 2016, 55 (12): 6344–6350
Inorg. Chem., 2016, 55 (12): 6344–6350