TY - JOUR
T1 - Electronic nature of zwitterionic alkali metal methanides, silanides and germanides-a combined experimental and computational approach
AU - Li, H.
AU - Aquino, A. J.A.
AU - Cordes, D. B.
AU - Hase, W. L.
AU - Krempner, C.
N1 - Funding Information:
This project was funded in part by the NSF (grant no. 1407681; Project SusChEM: IUPAC) as part of the IUPAC International Funding Call on ?Novel Molecular and Supramolecular Theory and Synthesis Approaches for Sustainable Catalysis?. The NSF is also thanked for purchase of a JEOL ECS-400 Spectrometer (CRIF-MU CHE-1048553). Support was also provided by the TTU Department of Chemistry & Biochemistry cluster Robinson whose purchase was funded by the NSF (CRIF-MU CHE-0840493). The support of our work by the Welch Foundation (D-0005) and the Vienna Scientific Cluster for computer time is greatly acknowledged as well.
Publisher Copyright:
© The Royal Society of Chemistry.
PY - 2017
Y1 - 2017
N2 - Zwitterionic group 14 complexes of the alkali metals of formula [C(SiMe2OCH2CH2OMe)3M], (M-1), [Si(SiMe2OCH2CH2OMe)3M], (M-2), [Ge(SiMe2OCH2CH2OMe)3M], (M-3), where M = Li, Na or K, have been prepared, structurally characterized and their electronic nature was investigated by computational methods. Zwitterions M-2 and M-3 were synthesized via reactions of [Si(SiMe2OCH2CH2OMe)4] (2) and [Ge(SiMe2OCH2CH2OMe)4] (3) with MOBut (M = Li, Na or K), resp., in almost quantitative yields, while M-1 were prepared from deprotonation of [HC(SiMe2OCH2CH2OMe)3] (1) with LiBut, NaCH2Ph and KCH2Ph, resp. X-ray crystallographic studies and DFT calculations in the gas-phase, including calculations of the NPA charges confirm the zwitterionic nature of these compounds, with the alkali metal cations being rigidly locked and charge separated from the anion by the internal OCH2CH2OMe donor groups. Natural bond orbital (NBO) analysis and the second order perturbation theory analysis of the NBOs reveal significant hyperconjugative interactions in M-1-M-3, primarily between the lone pair and the antibonding Si-O orbitals, the extent of which decreases in the order M-1 > M-2 > M-3. The experimental basicities and the calculated gas-phase basicities of M-1-M-3 reveal the zwitterionic alkali metal methanides M-1 to be significantly stronger bases than the analogous silanides M-2 and germanium M-3.
AB - Zwitterionic group 14 complexes of the alkali metals of formula [C(SiMe2OCH2CH2OMe)3M], (M-1), [Si(SiMe2OCH2CH2OMe)3M], (M-2), [Ge(SiMe2OCH2CH2OMe)3M], (M-3), where M = Li, Na or K, have been prepared, structurally characterized and their electronic nature was investigated by computational methods. Zwitterions M-2 and M-3 were synthesized via reactions of [Si(SiMe2OCH2CH2OMe)4] (2) and [Ge(SiMe2OCH2CH2OMe)4] (3) with MOBut (M = Li, Na or K), resp., in almost quantitative yields, while M-1 were prepared from deprotonation of [HC(SiMe2OCH2CH2OMe)3] (1) with LiBut, NaCH2Ph and KCH2Ph, resp. X-ray crystallographic studies and DFT calculations in the gas-phase, including calculations of the NPA charges confirm the zwitterionic nature of these compounds, with the alkali metal cations being rigidly locked and charge separated from the anion by the internal OCH2CH2OMe donor groups. Natural bond orbital (NBO) analysis and the second order perturbation theory analysis of the NBOs reveal significant hyperconjugative interactions in M-1-M-3, primarily between the lone pair and the antibonding Si-O orbitals, the extent of which decreases in the order M-1 > M-2 > M-3. The experimental basicities and the calculated gas-phase basicities of M-1-M-3 reveal the zwitterionic alkali metal methanides M-1 to be significantly stronger bases than the analogous silanides M-2 and germanium M-3.
UR - http://www.scopus.com/inward/record.url?scp=85011066954&partnerID=8YFLogxK
U2 - 10.1039/c6sc02390h
DO - 10.1039/c6sc02390h
M3 - Article
AN - SCOPUS:85011066954
VL - 8
SP - 1316
EP - 1328
JO - Chemical Science
JF - Chemical Science
SN - 2041-6520
IS - 2
ER -