Bernard Frange

Reaction of B11H14NR4 (REt, Bu) with M2O3 (MAs, Sb, Bi) in biphasic systems

Abstract The reaction of B 11 H 14 NR 4 (REt, Bu) with M 2 O 3 (MAs, Sb Bi) in biphasic systems H 2 O/CH 2 Cl 2 or NaOH/CH 2 Cl 2 , with C 6 H 5 NEt 3 Cl as phase transfer catalyst, was investigated as a new route to the already described icosahedral B 11 H 11 MNR 4 (MAs, Sb, Bi; REt, Bu). When the above reaction was performed in basic medium, besides the expected heteroboranes, a new anionic species could be isolated and characterized by its 1D 11 B, 1 H{ 11 B} and 2D 11 B 11 B NMR spectra. Consistently with these data the formula B 11 H 13 OB 11 H 13 2− ,2NEt 4 + is proposed, the anionic part consisting of two icosahedral fragments B 11 H 13 (eleven normal BH bonds and two bridge hydrogens in the open face) linked via a BOB bond; on both sides, the oxygen atom is attached, in endo position, to the unbridged boron atom of the open face. The same compound could be prepared by reaction of B 11 H 14 − with PO 4 HNa 2 , in NaOH/CH 2 Cl 2 mixtures. A possible path involving a mild oxidation of B 11 H 13 2− by M 2 O 3 (MAs, Sb, Bi) is suggested.

Oxygen in an electron-deficient borane skeleton: the oxa-nido-dodecaborate anion [OB11H12]–

B11H14–in aqueous sodium hydroxide reacts with oxygen to give OB11H12–, the first example of an oxaborane species where oxygen is part of the boron–hydrogen cluster.

Simplified synthesis of B-trichloro N-trialkylborazines (ClBNR)3, R = Me, Et, and of heterocycles related to 1,3-diaza-2,4-diboranaphthalene (ClBNC6H5)2

Abstract A 1/1 mixture of the tertiary amine boron trichloride adduct BDMA·BCl3 (BDMA = N,N-dimethylbenzylamine) and the amine hydrochloride RNH2·HCl (R = Me, Et) was heated in refluxing chlorobenzene to give the B- trichloro N-trialkylborazines (ClBNR)3 (R = Me, Et) with very good yield. With NH4Cl, the same reaction failed to give the related trimeric species (ClBNH)3, the latter compound being obtained in small amounts when the adduct ODMA·BCl3 (ODMA = N,N-dimethyloctylamine) is used instead of BDMA·BCl3 When applied to C6H5NH2·HCl, the same reaction leads to the expected borazine (ClBNC6H5)3 with moderate yield (23%), the main compound (77% according to 1H NMR) being a boron-nitrogen heterocycle derived from 1,3-diaza-2,4- diboranaphthalene (C6H5NBCl)2. Attempted isolation of the latter compound by chromatographic methods was unsuccessful. All these derivatives were characterized by high resolution 11B, 1H and 13C NMR.

A New Synthetic Approach to Boron Triisothiocyanate-Tertiary Amine Adducts and Related Species

Abstract The reaction of the adduct BDMA.BC13 (BDMA = N.N dimethylbenzylamine) with KNCS in refluxing, toluene, with tetraglyme added, was found as a very convenient route to BDMA.B(NCS)3. Further, according to the stoichiometry, either mixed species BDMA.BC1n(NCS)3-n(n = 1,2) or K+|B(NCS)4|−, were also obtained. The same reaction was applied to KF and KNCO as well as to other tertiary alkylamines.

Adducts of trichloroborane with cyanamides. Thermal degradation to boron nitride

Abstract H 2 NCN reacts with BCl 3 at low temperatures to give the complex H 2 NCNBCl 3 ( 1 and the dimeric iminoborane [H 2 NC(Cl)NBCl 2 ] 2 ( 3 ), whereas Me 2 NCN and BCl 3 yield mainly [Me 2 NC(Cl)NBCl 2 ] 2 ( 4 ). The cyanamide complex 1 and the iminoborane 3 release HCl when heated above 100°C, and the pyrolysis of 1 or 3 at 1000°C in the presence of NH 3 leads to the formation of boron nitride. Promising results concerning resistance of graphite against oxidation were obtained when graphite was covered with a layer of dissolved 3 and pyrolysed under NH 3 at 1000°C with additional heating in vacuo at 1350°C.