TY - JOUR
T1 - Charge Transfer via the Dative N-B Bond and Dihydrogen Contacts. Experimental and Theoretical Electron Density Studies of Small Lewis Acid-Base Adducts
AU - Mebs, S.
AU - Grabowsky, Simon
AU - Foerster, D.
AU - Kickbusch, R.
AU - Hartl, M.
AU - Daemen, L.L.
AU - Morgenroth, W.
AU - Luger, P.
AU - Paulus, B.
AU - Lentz, D.
PY - 2010
Y1 - 2010
N2 - The electronic characteristics of the dative N-B bond in three Lewis acid-base adducts, hydrazine borane, hydrazine bisborane, and ammonia trifluoroborane, are analyzed by an approach combining experimental electron density determination with a broad variety of theoretical calculations. Special focus is directed to the weak dihydrogen contacts in hydrazine borane. The Atoms In Molecules partitioning scheme is complemented by additional methods like the Source Function, and the Electron Localizability Indicator. For the multipole-free theoretical models of hydrazine borane and hydrazine bisborane, a weak charge donation from Lewis base to acid of about 0.05 e is found, whereas multipole refinement of theoretical and experimental structure factors resulted in opposite signs for the Lewis acid and base fragments. For ammonia trifluoroborane, the donation from Lewis base to acid is slightly larger (about 0.13 e) in the multipole-free models, and the charges obtained by multipole refinement retain the direction of the charge donation but show quite large variations. The natural population analysis charges predict larger charge donations (similar to 0.35 e) from the Lewis bases to the acids for the three title complexes. Although the three compounds exhibit intermolecular interactions of different types and strengths, including classical hydrogen bonds, F center dot center dot center dot H contacts and the already mentioned dihydrogen bonds, almost no charge transfer is detected between different molecules within the crystal environment. The main electronic effect of the formation of the Lewis acid-base adducts and of the crystallization is an increase in the charge separation within the ammonia/hydrazine fragments, which is supported by all investigated bond and atomic properties. The nature of the dative N-B bond is found to be mainly electrostatic, but with a substantial contribution of covalency. The F-B bonds show similarities and differences from the N-B bonds, which makes a distinction of coordinative (or dative) bonds from polar covalent interactions possible.
AB - The electronic characteristics of the dative N-B bond in three Lewis acid-base adducts, hydrazine borane, hydrazine bisborane, and ammonia trifluoroborane, are analyzed by an approach combining experimental electron density determination with a broad variety of theoretical calculations. Special focus is directed to the weak dihydrogen contacts in hydrazine borane. The Atoms In Molecules partitioning scheme is complemented by additional methods like the Source Function, and the Electron Localizability Indicator. For the multipole-free theoretical models of hydrazine borane and hydrazine bisborane, a weak charge donation from Lewis base to acid of about 0.05 e is found, whereas multipole refinement of theoretical and experimental structure factors resulted in opposite signs for the Lewis acid and base fragments. For ammonia trifluoroborane, the donation from Lewis base to acid is slightly larger (about 0.13 e) in the multipole-free models, and the charges obtained by multipole refinement retain the direction of the charge donation but show quite large variations. The natural population analysis charges predict larger charge donations (similar to 0.35 e) from the Lewis bases to the acids for the three title complexes. Although the three compounds exhibit intermolecular interactions of different types and strengths, including classical hydrogen bonds, F center dot center dot center dot H contacts and the already mentioned dihydrogen bonds, almost no charge transfer is detected between different molecules within the crystal environment. The main electronic effect of the formation of the Lewis acid-base adducts and of the crystallization is an increase in the charge separation within the ammonia/hydrazine fragments, which is supported by all investigated bond and atomic properties. The nature of the dative N-B bond is found to be mainly electrostatic, but with a substantial contribution of covalency. The F-B bonds show similarities and differences from the N-B bonds, which makes a distinction of coordinative (or dative) bonds from polar covalent interactions possible.
U2 - 10.1021/jp100995n
DO - 10.1021/jp100995n
M3 - Article
C2 - 20726618
SN - 1089-5639
VL - 114
SP - 10185
EP - 10196
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
ER -