9-H-9-Borafluorene dimethyl sulfide adduct: a product of a unique ring-contraction reaction and a useful hydroboration reagent

Abstract

The dimethyl sulfide adduct 2(DMS) is a crystalline storage form of the unstable hydroboration reagent 9-H-9-borafluorene (2); 2(DMS) is available by the addition of DMS to either in situ generated [2](2) or 1,2-(2,2'-biphenylylene)diborane(6) (7).

Marriage of heavy main group elements with π-conjugated materials for optoelectronic applications

“…1). 32 Following a similar strategy as used to prepare borafluorenes 25,26,33,34 these Ga and In heterofluorenes were prepared by a general salt elimination reaction between 2,2'-dilithiobiphenyl and Mes*ECl 2 (E = Ga and In). The molecular structure of 1 was determined by X-ray crystallography, however no supporting optical or electrochemical studies were reported for either species.…”

Confirmation of an Early Postulate: BCB Two‐Electron–Three‐Center Bonding in Organo(hydro)boranes

“…[9] In situ NMR spectroscopy augmented by DFT calculations led us to assign a structure to this shortlived intermediate in which two molecules of A form an unusual C 1 -symmetric dimer (A) 2 with a B-B-bridging aryl ring. [9,10] Even though the low stability of (A) 2 precluded any further characterization, we considered this species a stimulating lead structure in the quest for isolable BÀC(aryl)ÀBbridged molecules. Aiming at the kinetic stabilization of (A) 2 , we introduced bulky tert-butyl substituents at the phenylene rings and prepared 2,7-di-tert-butyl-9-bromo-9-borafluorene (1; Scheme 1 b) [22] from 2,7-di-tert-butyl-9,9-dimethyl-9-silafluorene [11] and BBr 3 .…”

Radical chain reactions involving 9-alkyl-9-borafluorenes

“…16 Borane 3 is particularly unstable due to its antiaromatic character and it tends to reversibly form a dimer and to rapidly degrade, affording isomers and oligomers that exclude boron's empty p-orbital from the π-plane. 14,16,17,18 The mechanisms of isomerization and polymerization have been studied. 16,17,18 Unsymmetrical borafluorenes, synthesized by boron insertion in C-H 19 and C-C 20 bonds, and fluorinated 9-borafluorenes 21 were also studied.…”

“…14,16,17,18 The mechanisms of isomerization and polymerization have been studied. 16,17,18 Unsymmetrical borafluorenes, synthesized by boron insertion in C-H 19 and C-C 20 bonds, and fluorinated 9-borafluorenes 21 were also studied. When 9-H-9-borafluorene 3 was placed in the presence of ethylene, hydroboration was observed.…”

“…14 In the case of a terminal alkyne, mono or double hydroboration were observed. 16 To circumvent the stability problem of compound 3, pyridine 16 and dimethylsulfide 18 stabilized complexes of the 9-H-9-borafluorene 3 were prepared from 9-chloro-9-borafluorene 2 in nearly quantitative yield. The complex 3·SMe 2 was claimed to be a storable adduct of the reagent 3 (it does not oligomerize) and could be directly used for the hydroboration of alkynes (Scheme 3).…”