Zur Chemie und Konstitution borsaurer Salze. IV. Über die Bildung von Methoxoboraten durch Methanolyse der Alkaliborate

Abstract

Die Borate der Alkalien, auch wasserhaltige, lösen sich in Methanol unter Bildung der Methoxoborate, Me[B(OCH3)4], und Wasser z. B. nach MeIBO2 + 4 CH3OH → MeB(OCH3)4 + 2 H2O. Alkaliborate mit einem Basen‐Säure‐Verhältnis < 1 liefern neben dem Methoxoborat die dem Überschuß an Bor entsprechende Menge an B(OCH3)3. Die thermische Beständigkeit der kristall‐alkoholfreien Substanzen wächst vom Lithium zum Natrium und fällt zum Caesium hin ab.

Alkali metal alkoxyborate ester salts; a contemporary look at old compounds

“…During the mid-20 th century, the synthesis of alkali metal tetraalkoxyborate salts (M[B(OR) 4 ]) was of major interest. 3,4,6,7 Synthesis of the different alkoxyborate salts had to be performed using three different methods: alcoholysis of sodium borohydride and potassium borohydride (NaBH 4 , KBH 4 ), transesterification of sodium tetramethoxyborate (Na[B (OMe) 4 ]) and alcohol (ROH), and the combination reaction of alkylborate ester (B(OR) 3 ) and alkali metal alkoxide (MOR) (Table 1). In order to synthesise Na[B(OMe) 4 ] and potassium tetramethoxyborate (K[B(OMe) 4 ]), NaBH 4 or KBH 4 was mixed 1).…”

“…The excess solvent was removed under vacuum and dried at 40 °C as previous literature had stated Li[B(OMe) 4 ] decomposed at temperatures above 50 °C. 4 Samples were then stored in an argon filled glovebox (yield 1.30 g, 70%) (Fig. S14-S18 †).…”

“…The thermal behavior of the tetraalkoxyborate salts has been analyzed using Differential Scanning Calorimetry, Thermogravimetric Analysis (DSC-TGA), Residual Gas Analysis-Mass Spectroscopy (RGA-MS), Temperature Programmable Photographic Analysis (TPPA) and Synchrotron Radiation X-Ray Diffraction (SR-XRD) and have been outlined in Table 3. According to Lehmann and Tiess in 1960, 4 Na[B(OMe) 4 ] decomposes to NaOMe and B(OMe) 3 beginning at 200 °C. 4 Analysis of the thermal properties indicated that Na[B(OMe) 4 ] has a more complicated thermal behavior than previously identified.…”

“…According to Lehmann and Tiess in 1960, 4 Na[B(OMe) 4 ] decomposes to NaOMe and B(OMe) 3 beginning at 200 °C. 4 Analysis of the thermal properties indicated that Na[B(OMe) 4 ] has a more complicated thermal behavior than previously identified. Firstly, DSC (5 K min −1 , 40 mL min −1 Ar) from 50 °C to 500 °C, indicated endothermic events at 177 °C and 264 °C, as well as exothermic events at 316 and 378 °C (Fig.…”

“…5,6 However, it is important to note that these methods focused on the primary alcohols, methanol, ethanol, and 1-propanol (PrOH). [1][2][3][4][5][6] Attempts to synthesise sodium tetraalkoxyborate salts via the reaction of sodium borohydride and pure secondary and tertiary alcohols, isopropanol ( i PrOH) and tertbutanol ( t BuOH), showed no reaction after 24 hours. 5 However, it was possible to synthesise triisopropoxyborate (B(O i Pr) 3 ) and tritertbutoxyborate (B(O t Bu) 3 ) from the reaction of NaBH 4 in the presence of acetic acid.…”