The Chemistry of [1,1′‐bis(o‐Carboranyl)]Borane η²‐σ‐Silane Adduct

Abstract

We report here a new route for the preparation of [1,1′‐bis(o‐carboranyl)]borane, a 3D analogue of 9‐borafluorene, η2‐σ‐silane adduct (1‐H‐SiEt3) in high yields (>80 %). The nature of B−H−Si bonding was studied by density functional theory (DFT) computations. Preliminary reactivity study of 1‐H‐SiEt3 with small molecules was carried out. Interestingly, 1‐H‐SiEt3 reacts with benzophenone in hexane producing the deoxygenation product Ph2CH2. While in benzene, 1‐H‐SiEt3 reacts with benzophenone leading to mixture of Ph2CH2 and Ph3CH (3 : 1). Ph3CH is formed via addition of benzene to the carbonyl followed by deoxygenation. In contrast, the reaction of benzophenone with Et3SiH in presence of a catalytic amount of 1‐H‐SiEt3 leads to hydrosilylation product Ph2(H)C−OSiEt3.

The Effect of Carborane Substituents on the Lewis Acidity of Boranes

“…50,51,76−87 Carboranes are considered to be 3D analogues of benzene, so accordingly, carborane that contains analogues of fluorene and anthracene have been targeted. The Ye 88 and Dobrovetsky 89 groups, along with our group, 90 have reported bis-ortho-carboranyl-borane analogues of a 9-borafluorene with various substitutions on boron (7). The diisopropylamino and mesityl species were not classified as Lewis superacids due to π-donation and bulk, respectively, but Br, Cl, and Ph were all classified as Lewis superacids (LSAs).…”

“…Marder, Braunschweig, and co-workers reported the mono- and bis-borafluorene ortho -carboranyl species 5 and 6 , that are both susceptible to endocyclic B–C bond cleavage or insertion to access heterocycles, which are, in many cases, similar to 9-borafluorenes with B-aryl or B-halo substitutions. ,,− Carboranes are considered to be 3D analogues of benzene, so accordingly, carborane that contains analogues of fluorene and anthracene have been targeted. The Ye and Dobrovetsky groups, along with our group, have reported bis- ortho -carboranyl-borane analogues of a 9-borafluorene with various substitutions on boron ( 7 ). The diisopropylamino and mesityl species were not classified as Lewis superacids due to π-donation and bulk, respectively, but Br, Cl, and Ph were all classified as Lewis superacids (LSAs).…”

Synthesis and cluster structure distortions of biscarborane dithiol, thioether, and disulfide

“…the formation of five-member rings with both cluster carbon atoms bound to either a transition metal center or a heteroatom. [42][43][44][45][46][47][48][49] To the best of our knowledge, there has been only one report in the literature of the attachment of pairs of donor groups (dihydro-1,2-oxazines) to two carbon atoms of biscarborane. 50 In our previous work, we reported the attempt to install two phosphine groups on both carbon atoms of biscarborane, which, instead of the target diphosphine, led to intramolecular B-H bond activation driven by the reduction of one of the boron clusters.…”