Deprotonation of a Seemingly Hydridic Diborane(6) To Build a B−B Bond

Abstract

Deprotonation of the doubly arylene-bridged diborane(6) derivative 1H with (Me Si) CLi or (Me Si) NK gives the B-B σ-bonded species M[1H] in essentially quantitative yields (THF, room temperature; M=Li, K, arylene=4,4'-di-tert-butyl-2,2'-biphenylylene). With nBuLi as the base, the yield of Li[1H] drops to 20 % and the 1,1-bis(9-borafluorenyl)butane Li[2H] is formed as a side product (30 %). In addition to the 1,1-butanediyl fragment, the two boron atoms of Li[2H] are linked by a μ-H bridge. In the closely related molecule Li[3H], the corresponding μ-H atom can be abstracted with (Me Si) CLi to afford the B-B-bonded conjugated base Li [3] (THF, 150 °C; 15 %). Li[1H] and Li[2H] were characterized by NMR spectroscopy and X-ray crystallography.

Doping Polycyclic Aromatics with Boron for Superior Performance in Materials Science and Catalysis

“…As a fundamental change of paradigm, the successful deprotonation of 56 b with concomitant formation of [ 64 ] − has been reported (Scheme ). In the presence of [(Me 3 Si) 3 C] − or [(Me 3 Si) 2 N] − as a base, one of the B−H−B bridges is transformed into a B−B bond, which is a unique strategy for the coupling of two boron atoms …”

A redox-active diborane platform performs C(sp3)–H activation and nucleophilic substitution reactions

“…The anions [ 1 H] – and [ 1 ] 2– are accessible in good yields via alkali-metal reduction of 1 H 2 . 12 – 14 Stepwise protonation with ethereal HCl cleanly takes [ 1 ] 2– back to [ 1 H] – and finally 1 H 2 . 14 The reverse deprotonation reaction of 1 H 2 to afford [ 1 H] – is also quantitative, provided that the sterically demanding bases (Me 3 Si) 2 NLi and (Me 3 Si) 3 CLi are used.…”

“… 12 – 14 Stepwise protonation with ethereal HCl cleanly takes [ 1 ] 2– back to [ 1 H] – and finally 1 H 2 . 14 The reverse deprotonation reaction of 1 H 2 to afford [ 1 H] – is also quantitative, provided that the sterically demanding bases (Me 3 Si) 2 NLi and (Me 3 Si) 3 CLi are used. In case of the smaller n BuLi, the deprotonation reaction (20%) is accompanied by the formation of an anionic diborylmethane featuring a boron-bridging hydrogen atom (30%; Scheme 1 , R = C 3 H 7 ).…”

The 9H‐9‐Borafluorene Dianion: A Surrogate for Elusive Diarylboryl Anion Nucleophiles

“…[26] It has been shown previously that M[3H] reacts with alkali metals M to afford the diborene M 2 [3] (see Figure 2 a). [24,30] We therefore propose that the hydride transfer between Na 2 [2] and 1·THF paves the way to the formation of the side products generated in the room-temperature reduction of 1·THF. The sole purpose of the low-temperature step is therefore to reductively quench the Lewis acidity of 1·THF under conditions where its reaction with Na 2 [2] is kinetically prohibited.…”