The reaction of boron trichloride – tertiary amine adducts with pseudohalide salts under phase transfer catalysis conditions

Abstract

The reaction of boron trichloride – tertiary amine adducts D•BCl3 with pseudohalide salts MX was investigated in a homogeneous medium or in two-phase systems under liquid/liquid or solid/liquid phase transfer catalysis conditions (PTC) as a potential route to the adducts D•BX3 (X = NCS, NCO). Best results were obtained with solid/liquid PTC with tetraglyme as catalyst. By suitable choice of the tertiary amine, solvent, and stoichiometry, the symmetric compounds D•BX3 were thus prepared with good yields, the same reaction leading either to mixed species D•BX3-nCln (n = 1, 2; X = NCS, NCO) or to the tetrapseudohaloborate anions BX4− + (X = NCS, NCO). The mixed tetrahaloborates BX4-n Yn− could be obtained by exchange reaction from BX4− + BY4− (X = NCS, Y = F, Cl, Br) or from BY3 + Bu4NX (X = NCS; Y = F, Cl, Br; X = NCO; Y = F). All these compounds were characterized by 11B and, in one case, by 1H and 13C NMR. Pairwise additivity is observed for the 11B NMR chemical shifts.