High‐Yield Syntheses of Sodium, Potassium, and Thallium Hydrotris[3,5‐bis(trifluoromethyl)pyrazolyl]borates and the X‐ray crystal structure of {hydrotris[3,5‐bis(trifluoromethyl)pyrazolyl]borato} thallium(I)

Abstract

An improved synthesis of 3,5‐bis(trifluoromethyl)pyrazole (1) is described. This compound was used for the high‐yield syntheses of the tris(pyrazoly1)borates Nd[HB(3,5‐(CF3),‐pz)3] (2a) and the corresponding potassium salt, 2b, starting from 1 and NaBH4 and KBH4, respectively. A convenient route to the corresponding thallium(I) salt, 2c, using thallium(I) acetate and either 2a or 2b in CHCI3, is also described. The sodium (3a), potassium (3b), and thallium (3c) salts of bis(pyrazolyl)borate [H2B(3,5‐(CF3)2‐pz)2]− were also prepared. The above pyrazolylborates were characterized by 1H‐, 13C‐, 19F‐, and 11B‐NMR spectroscopy. The X‐ray crystal structure of the thallium derivative 2c was determined. The compound crystallizes in the monoclinic space group P21/m with a = 8.248(9) Å, b = 15.034(12) Å c = 9.243(8) Å, β = 100.10(7)°, Z = 2. The Tl‐atom adopts a pyramidal geometry with respect to the three N‐atoms. However, two TI–N distances (2.725(7) Å) are longer than the third (2.675(10) Å). Copyright © 1995 Verlag GmbH & Co. KGaA, Weinheim