BF4− as source for the preparation of BF2 bridged copper(II) dimethylglyoxime complexes

Abstract

AbstractThe reaction of copper(II) tetrafluoroborate with dimethylglyoxime (H2dmg) leads to the formation of the dinuclear complexes [Cu2(dmg)(Hdmg)(EtOH)(H2dmg)]BF4 (1) and [Cu2(dmg ⋅ BF2)(Hdmg)(H2dmg)]BF4 (2). In 2, BF2 deriving from BF4− has been inserted into the oxime groups to form an O,O‐bidentate difluoroboron complex. Co‐crystallization of 1 and 2 impeded a thorough characterization of 2. In further attempts to prepare pure 2, the difluoroboron complexes [Cu(dmg ⋅ BF2)2(MeCN)] (3) and [Cu(dmg ⋅ BF2)(Hdmg)] (4) have been obtained. Attempts to isolate the BF2‐bridged ligand failed. Even though BF4− readily is decomposed to formally form BF2+ that is inserted into the resulting complexes and F−, the nascent F− ions are not a suitable F− source for organic fluorination reactions. Nevertheless, the described, facile route to prepare O,O‐bidentate difluoroboron complexes without the usage of the highly toxic BF3 ⋅ OEt2 but BF4− instead is of interest for synthetically working chemists.