“…A notable deviation from the common [Bϕ 3 ] planar triangles and [Bϕ 4 ] tetrahedra is the presence of highly distorted, four-coordinated boron oxyanions, which contain three normal B–O bonds of ∼1.48 Å ,, and one anomalously long B–O bond from 1.54 to 1.69 Å. − These boron oxyanions deviate significantly from the tetrahedral symmetry and are best described as approximate trigonal pyramids (hereafter denoted as [OBO 3 ]). ,, Previous solid-state 11 B nuclear magnetic resonance (NMR) studies ,,− showed, on the one hand, that the [Bϕ 4 ] groups in borates are characterized by 11 B isotropic chemical shifts (δ iso ) close to 0 ppm and the nuclear quadrupole parameter C Q invariably less than 0.5 MHz, reflecting the approximately tetrathedral symmetry. The [Bϕ 3 ] groups, on the other hand, have a somewhat wide range of δ iso ( 11 B) values from 15 to 25 ppm, but the C Q ( 11 B) values are clustered around 2.5 MHz. ,,− The δ iso ( 11 B) variations of the [Bϕ 3 ] groups in borates and borosilicates have been correlated with various structural characters of both the first and outer shells (e.g., FBBs, next-nearest-neighbor cations, hydrogen bonding, etc. ). − However, the reported δ iso ( 11 B) values of four-coordinated boron oxyanions in borates vary by less than 2 ppm, ,,,,, making their NMR resolution difficult.…”