Synthesis and Crystal Structure of the High-pressure Cobalt Borate HP-CoB₂O₄

Toward the Coordination Fingerprint of the Edge-Sharing BO4 Tetrahedra

“…At first, the high-pressure (HP) condition appears to be a key condition to form the B 2 O 6 units. Indeed, the majority of borates with (es-)­BO 4 tetrahedra, discovered by Huppertz et al, were synthesized at HP and high temperature (HT), − with the first one published in 2002 . Similarly, α-Ba 3 [B 10 O 17 (OH) 2 ] was synthesized at HP through hydrothermal reactions at 500 °C and 1000 bar .…”

“…The boron framework is varied by replacing the six nodes with different types of B–O blocks. The B–O blocks may be linked to two external nodes [Co 7 B 24 O 42 (OH) 2 ·2H 2 O or BaAlBO 4 ], four external nodes [HP-MB 2 O 4 where M = Ni, β-Fe, and Co, M 4 B 6 O 15 where M = Dy, and Ho, HP-La 3 B 6 O 13 (OH) 6 , α-M 2 B 4 O 9 where M = Y, Sm, Eu, Gd, Tb, and Ho, KZnB 3 O 6 , Ba 4 Na 2 Zn 4 B 18 O 36 , and Li 4 Na 2 CsB 7 O 14 ], or a combination of two nodes from the common edge and two external nodes (α-Ba 3 [B 10 O 17 (OH) 2 ]). The case where all six available nodes are linked to B–O blocks is encountered in HP-CsB 5 O 8 , HP-MB 3 O 5 where M = K, Rb, and Tl, (NH 4 ), Cs 0.4 (H 3 O) 0.6 , and β-CsB 9 O 14 .…”

HP‐KB3O5 Highlights the Structural Diversity of Borates: Corner‐Sharing BO3/BO4 Groups in Combination with Edge‐Sharing BO4 Tetrahedra

“…[2,3] Most striking was the discovery of edge-sharing BO 4 Meanwhile, this motif was observed in three different structure types represented by the high-pressure compounds RE 4 B 6 O 15 (RE = Dy, Ho), [4,5] α-RE 2 B 4 O 9 (RE = SmHo), [6][7][8] and β/HP-MB 2 O 4 (M = Fe, Ni, Co). [9][10][11] With the compounds M 6 B 22 O 39 ·H 2 O (M = Fe, Co), intermediate states between corner-and edge-sharing BO 4 tetrahedra could also be isolated. [12] To our astonishment, the structural feature of edge-sharing BO 4 tetrahedra was recently found in the compound KZnB 3 O 6 , synthesized under ambient pressure conditions.…”

Oxonium Ions Substituting Cesium Ions in the Structure of the New High‐Pressure Borate HP‐Cs1−x(H3O)xB3O5 (x=0.5–0.7)

“…The B 2 O 6 group formed by two edge-sharing BO 4 tetrahedra in Dy 4 B 6 O 15 was one of the most striking discoveries in the high-pressure chemistry of borates. [8,9] Meanwhile, this structural motif was found in several other high-pressure phases, for example, HP-MB 2 O 4 (M = Ni, [10] Co [11] ) and a-(RE) 2 B 4 O 9 (RE = SmHo). [12,13] Until 2009, edge-sharing BO 4 tetrahedra were only observed in borates synthesized under high-pressure conditions, and thus their occurrence was assumed to be restricted to the domain of high-pressure chemistry.…”