OJPC> Vol.5 No.1, February 2015

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Henk M. Buck

Kasteel Twikkelerf 94, Tilburg, The Netherlands.

Recently a mechanistic understanding of the pressure-and/or temperature-induced coordination change of boron in a borosilicate glass has been demonstrated by Edwards et al. In situ high-pressure ¹¹B solid-state NMR spectroscopy has been used in combination with ab initio calculations in order to obtain insight in the molecular geometry for the pressure-induced conversion. The results indicate a deformation of the B(OH)₃ planar triangle, under isotropic stress, into a trigonal pyramid that serves as a precursor for the formation of a tetrahedral boron configuration. From our point of view, the deformation controlling the out-of-plane transition of boron accompanied with a D_3h into C_3v geometric change is an interesting transformation because it matches with our molecular description based on Van’t Hoff modelling for the tetrahedral change of carbon in CH₃X by substitution of X with nucleophiles via a trigonal bipyramid state in which the transferred carbon is present as a methyl planar triangle “cation”. Van’t Hoff modelling and ab initio calculations have been also applied on the dynamics of the out-of-plane geometry of a transient positively charged carbon in a trigonal pyramidal configuration into a planar trivalent carbon cation. Finally the same model is also used for the C_3v trigonal pyramidal configurations as NH₃ of the group 15 elements in their nucleophilic abilities.

Pressure-Induced Coordination, Van’t Hoff Modelling, Ab Initio Calculations, Reaction Dynamics

Buck, H. (2015) Interconversion between Planar-Triangle, Trigonal-Pyramid and Tetrahedral Configurations of Boron (B(OH)₃ -B(OH)₄^- ), Carbon (CH₃⁺ -CH₃X) and for the Group 15 Elements as Nitrogen (NH₃-NH₄⁺ ). A Modelling Description with Ab Initio Results and Pressure-Induced Experimental Evidence. Open Journal of Physical Chemistry, 5, 1-8. doi: 10.4236/ojpc.2015.51001.