TY - JOUR
T1 - Nuclear magnetic shielding of monoboranes
T2 - calculation and assessment of 11B NMR chemical shifts in planar BX3 and in tetrahedral [BX4]- systems
AU - Machacek, Jan
AU - Buehl, Michael
AU - Fanfrlik, Jindrich
AU - Hnyk, Drahomir
N1 - The financial support of the Czech Science Foundation (project No. 17-08045S) is gratefully acknowledged.
PY - 2017/12/21
Y1 - 2017/12/21
N2 - 11B NMR chemical shifts of tricoordinated BX3 and tetracoordinated BX4- compounds (X = H, CH3, F, Cl, Br, I, OH, SH, NH2, and CH=CH2) were computed and the shielding tensors were explored not only within the nonrelativistic GIAO approach but also by applying both relativistic ZORA computations including spin-orbit coupling as well as by employing scalar nonrelativistic ZORA computations (BP86 level of density functional theory). The contributions of the spin-orbit coupling to the overall shieldings are decisive for X = Br and I in both series. No relationship was found between the 2p orbital occupancies or 1/∆E (difference between LUMO and suitably occupied MO that can be coupled with LUMO) with the shielding tensors (or their principal values) in the BX3 series. However, a multidimensional statistical approach known as factor analysis (frequently used in chemometrics) revealed that three factors account for 92 % of the cumulative proportion of total variance. The main components of the first factor are occupancies in the 2px and 2py orbitals and 1/∆E, the second factor is mainly the occupancy in the 2pz orbital and the inductive substituent parameters by Taft and, finally, the third factor consists exclusively (99.3 %) of the electrostatic potentials (Vmax), which is directly related to the so-called π-hole magnitudes.
AB - 11B NMR chemical shifts of tricoordinated BX3 and tetracoordinated BX4- compounds (X = H, CH3, F, Cl, Br, I, OH, SH, NH2, and CH=CH2) were computed and the shielding tensors were explored not only within the nonrelativistic GIAO approach but also by applying both relativistic ZORA computations including spin-orbit coupling as well as by employing scalar nonrelativistic ZORA computations (BP86 level of density functional theory). The contributions of the spin-orbit coupling to the overall shieldings are decisive for X = Br and I in both series. No relationship was found between the 2p orbital occupancies or 1/∆E (difference between LUMO and suitably occupied MO that can be coupled with LUMO) with the shielding tensors (or their principal values) in the BX3 series. However, a multidimensional statistical approach known as factor analysis (frequently used in chemometrics) revealed that three factors account for 92 % of the cumulative proportion of total variance. The main components of the first factor are occupancies in the 2px and 2py orbitals and 1/∆E, the second factor is mainly the occupancy in the 2pz orbital and the inductive substituent parameters by Taft and, finally, the third factor consists exclusively (99.3 %) of the electrostatic potentials (Vmax), which is directly related to the so-called π-hole magnitudes.
U2 - 10.1021/acs.jpca.7b09831
DO - 10.1021/acs.jpca.7b09831
M3 - Article
SN - 1089-5639
VL - 121
SP - 9631
EP - 9637
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 50
ER -