Boron-Pyrazole Chemistry

Chemistry of the p-block elements with anionic scorpionate ligands

“…1 H NMR studies [19] show single environments for both the methyl and pyrazole protons from room temperature to -90 °C. This could be interpreted as either a highly fluxional 4-coordinate complex with a mobile 2 -coordinated ligand or as a 5-coordinate complex with a static 3 -coordinated ligand.…”

“…The pyrazole borate anions, first reported by Trofimenko in 1966 [1], have become immensely popular as ligands in the ensuing decades, and have become known as scorpionates in recognition of the resemblance of their coordination modes to a scorpion trapping its prey. The first generation of these anionic N-donor ligands (Chart 1), namely hydridotris(pyrazolyl)borate (Tp), tetrakis(pyrazolyl)borate (pzTp) and hydridotris (3,5-dimethylpyrazolyl)borate (Tp * ) laid the basis for an extensive chemistry, with complexes now known for the majority of the metallic elements.…”

The Stability of Mercaptobenzothiazole Based Soft Scorpionate Complexes

“…A schematic representation of the developments in scorpionate chemistry. From left to right: hydrotris(pyrazolyl)borate (Tp) (far left) [1,2]; the soft scorpionates hydrotris(methimazolyl)borate (Tm R ; R = Me, Ph, t Bu, etc)(centre left, top) [4,5] and hydrotris(mercaptobenzothiazolyl)borate (Tbz)(centre left, below) [9]; selenium and oxygen donor systems (centre right) [6,14,15]; and the poly(alkylthioalkyl)borates (right) [3,16]. The tetrakis(thioalky)borate anion (top right) was the first alternative soft donor system to be reported [3].…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Not only has there been an increase in the range of heterocycles employed (benzoimidazole-2-thione, 6 1,3,4-thiadiazole-2-thione, 7,8 benzothiazole-2-thione, 9 thiazolidine-2-thione, 9,10 1,2,4-triazole-5-thione, 11 pyridine-2-thione, 12 pyridazine-2-thione 13 ) but the range of donor atoms has also expanded, with systems containing nitrogen, 1,2,6 , sulfur, [3][4][5][6][7][8][9][10][11][12][13] selenium, 14,15 oxygen 6 and phosphorus 16 donors (Figure 1) having all been reported. The chemistry being generated using these species is diverse, but within the reports on the complexes of soft scorpionates are results which suggest that in some circumstances these ligands may be prone to decomposition.…”

Ion-pair interactions between the methyl tris(1-pyrazolyl)gallato molybdenum, tricarbonyl anion, [MeGapz3]Mo(CO)3−, and the Na+ cation, and the reactivity of the anion toward RX molecules (where RX = HCl, DBr, MeI, or EtBr)

“…It is also closely related in properties to the RBpz3-ligands (R = H, alkyl, aryl, or pyrazolyl), introduced some time ago by Trofimenko (2). For …”