Syntheses, Structures, and Reactivities of N-Heterocyclic Carbene-Coordinated Aminoborane Complexes

Abstract

Recent research has attracted considerable attention toward N-heterocyclic carbene-coordinated boranes (NHCborane) and their B-substituted derivatives because of their unique characteristics. In the present work, we focused on the syntheses, structures, and reactivities of such types of amine complexes, [NHC•BH 2 NH 3 ]X ((NHC = IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and IMe (1,3-dimethylimidazol-2-ylidene); X = Cl, I, OTf). We have developed a synthetic method to access NHC•BH 2 NH 2 through the reaction of NaH with [IPr•BH 2 NH 3 ]I, which was synthesized by the reaction of IPr•BH 2 I with NH 3 . As a Lewis base, NHC•BH 2 NH 2 could further react with HCl or HOTf to produce the corresponding salts of [IPr•BH 2 NH 3 ] + . IPr• BH 2 NH 2 BH 2 X (X = Cl, I) were synthesized by the reaction of HCl/I 2 with IPr•BH 2 NH 2 BH 3 and then converted to [IPr• BH 2 NH 2 BH 2 •IPr]X (X = Cl, I) by reacting with IPr. The IMe-coordinated boranes reacted quite similarly. The preliminary results revealed that the introduction of the NHC molecule has a considerable impact on the solubility and reactivities of aminoboranes.

Preparation of Mono and Bis‐Hydrazino‐Substituted N‐Heterocyclic Carbene Boranes

“…In contrast to the inorganic/main group side, where NHC (or CAAC) complexation is a way to generate and/or stabilize numerous BN architectures, [25][26][27][28][29][30] there are much less BÀ N bonds-containing NHC-boranes that could be of use for organic chemistry. [31][32][33] In a collaborative effort with the groups of Curran and Mayr, we identified that NHC-boranes are good hydride donors, [34] which can in some cases hydroborate imines, although it was the minor product of the reaction.…”

“…In contrast to the inorganic/main group side, where NHC (or CAAC) complexation is a way to generate and/or stabilize numerous BN architectures, [25–30] there are much less B−N bonds‐containing NHC‐boranes that could be of use for organic chemistry [31–33] …”