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The Donor‐Stabilized Silylene Bis[ N , N ′‐diisopropylbenzamidinato(−)]silicon(II): Synthesis, Electronic Structure, and Reactivity
Author(s) -
Junold Konstantin,
Nutz Marco,
Baus Johannes A.,
Burschka Christian,
Fonseca Guerra Célia,
Bickelhaupt F. Matthias,
Tacke Reinhold
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201402483
Subject(s) - silylene , chemistry , reactivity (psychology) , cycloaddition , benzene , reaction coordinate , crystallography , silicon , crystal structure , computational chemistry , stereochemistry , organic chemistry , catalysis , alternative medicine , pathology , medicine
A convenient and robust synthesis of bis[ N , N ′‐diisopropylbenzamidinato(−)]silicon( II ) ( 1 ), a donor‐stabilized silylene, has been developed (35 g scale). To get further information about the reactivity profile of 1 , a series of oxidative addition reactions were studied. Treatment of 1 with PhSeSePh (SeSe bond activation), C 6 F 6 (CF activation), and CO 2 (CO activation/cycloaddition) yielded the neutral six‐coordinate silicon( IV ) complexes 10 , 11 , and 13 , respectively. Treatment of 1 with N 2 O resulted in the formation of the dinuclear five‐coordinate silicon( IV ) complex 12 (oxidative addition/dimerization), which contains a four‐membered Si 2 O 2 ring. Compounds 10 – 13 were characterized by NMR spectroscopic studies in the solid state and in solution and by crystal structure analyses. Silylene 1 is three‐coordinate in the solid state (from crystal structure analysis) and exists as the four‐coordinate isomer 1′ in benzene solution (from computational studies). Based on state‐of‐the‐art relativistic DFT analyses, the four‐coordinate species 1′ was demonstrated to be the thermodynamically favored isomer in benzene solution (favored by Δ G =6.6 kcal mol −1 over the three‐coordinate species 1 ). The reason for this was studied by bonding analyses of 1 and 1′ . Furthermore, the 29 Si NMR chemical shifts of 1 and 1′ were computed, and in the case of 1′ it was analyzed how this NMR spectroscopic parameter is affected by solvation. These studies further supported the assumption that the silylene is four‐coordinate in solution.