Heteroleptic carbazolato-barium hydroborates and a related separated ion pair

Abstract

The syntheses and characterisation of two molecular barium-hydroborate complexes supported by a bulky bis(imino)carbazolate ligand, namely [{CarbDipp}Ba(μ-H2Bpin)]3 (23) and [{CarbDipp}Ba(H2-9BBN).Et2O] (3.Et2O), are presented. These two complexes are obtained in high yields upon reaction of the amido precursor [{CarbDipp}BaN(SiMe3)2] (1) with the commercially available pinacolborane or [H-9BBN]2, respectively. The solid-state molecular structures of the complexes were solved, and show 23 to form a solvent-free cyclic trimer, whereas the monomeric 3.Et2O is solvated by one molecule of diethyl ether. Furthermore, the well-defined ion pair [{CarbDipp}Ba.(Et2O)2]+[H2N{B(C6F5)3}2]– (4), a rare occurrence of soluble barium cation, was also obtained in good yield upon treatment of 1 with Bochmann’s acid. Its X-ray structure was solved and reveals the absence of interaction between the metal cation and its counter-ion. Finally, the structure of the seven-coordinated, dicationic [Ba.(thf)7]2+[H2N{B(C6F5)3}2]–2 (5) is also presented.