A Hydride‐Substituted Homoleptic Silylborate: How Similar is it to its Diborane(6)‐Dianion Isostere?
Jannik Gilmer, Michael Bolte, A.V. Virovets, Hans-Wolfram Lerner, Felipe Fantuzzi, Matthias Wagner
Abstract
Abstract The B‐nucleophilic 9 H ‐9‐borafluorene dianion reacts with 9‐chloro‐9‐silafluorene to afford air‐ and moisture‐stable silylborate salts M[Ar 2 (H)B−Si(H)Ar 2 ] (M[ HBSiH ], M=Li, Na). Li[ HBSiH ] and Me 3 SiCl give the B−pyridine adduct Ar 2 (py)B−Si(H)Ar 2 ( (py)BSiH ) or the chlorosilane Li[Ar 2 (H)B−Si(Cl)Ar 2 ] (Li[ HBSiCl ]) in C 6 H 6 ‐pyridine or THF. In both cases, the first step is H − abstraction at the B center. The resulting free borane subsequently binds a py or thf ligand. While the py adduct is stable at room temperature, the thf adduct undergoes a 1,2‐H shift via the cyclic B( μ ‐H)Si intermediate BHSi , which is afterwards attacked at the Si atom by a Cl − ion to give Li[ HBSiCl ]. DFT calculations were employed to support the proposed reaction mechanism and to characterize the electronic structure of BHSi . Treatment of Li[ HBSiCl ] with the N‐heterocyclic carbene IMe introduces the neutral donor at the Si atom and leads to Ar 2 (H)B−Si(IMe)Ar 2 ( HBSi(IMe) ), a donor‐acceptor‐stabilized silylene.