Small boranes, carboranes, and heterocarboranes

Abstract

Dehalogenation of 1,2-dichloro-diborane(4) derivatives with Na/K alloy does not lead to planar cyclo-tetraboranes but to the blue puckered diisopropylamino compound and to the yellow 2,2,6,6-tetramethylpiperidino-tetraboratetrahedrane derivative, respectively. With smaller dialkylamino substituents, the formation of orange-red cyclo-hexaborane (BNMe 2 ) 6 and the green closo-hexaborane (BNEt 2 ) 6 is observed. When a 1:1 mixture of Me 2 NBCl 2 and [Me 2 N(Cl)B] 2 is dehalogenated, a small amount of colorless crystals of the planar diamond-shaped tetrabora-bicyclo-butane [(Me 2 N) 2 BB−BNMe 2 ] 2 is obtained. Its MO analysis reveals that eight framework electrons are used to form two 3c,2e σ bonds, one 4c,2e π bond, and one 4c,2e σ bond along the edges.A new approach to reactive closo-dicarbapentaboranes involves the hydroboration of dichloroboryl-tbutylacetylene with HBCl 2 leading to Me 3 CCH 2 C(BCl 2 ) 3 . On heating, it is transformed into the closo-dicarbapentaborane (Me 3 CCH 2 C) 2 (BCl) 3 , in which the chlorine atoms may be substituted to give new derivatives.By reacting B 2 Cl 4 with C 5 Me 5 -SiMe 3 the nido-1-borane-2,3,4,5,6-pentacarbahexaborane(6) is stabilized by the Lewis acid BCl 3 to give (MeC) 5 B−BCl 3 .Hydroboration of 3,4-bis(isopropylidene)-1,3-diborolanes leads to the formation of nido-2,3,5-tricarbahexaboranes(7), which may be deprotonated to give the corresponding anions isolobal with C 5 H 5 − . Heterotricarbahexaboranes are obtained when a 3,4-bis(dichloroboryl)-2,5-hexadiene derivative is reacted with heptamethyldisilazane and hexamethyl-disilthiane to give the corresponding 1,2,5-azadiborolane and thiadiborolane. Their hydroboration leads to the aza-and thia-nido-dicarbahexaboranes, respectively.

Synthesis and Applications of Perfunctionalized Boron Clusters

“…Prior to our involvement, the only nonhalogen-containing, perfunctionalized, six-membered closo -boron clusters were the neutral hypercloso -B 6 (NEt 2 ) 6 , with Berndt and co-workers also disclosing the synthesis and structure of the dimethyl analogue, hypercloso -B 6 (NMe 2 ) 6 . Given our interest in the development of chemistry and applications of perfunctionalized boron clusters, − we reexamined the reactivity of the closo -[B 6 H 7 ] − anion.…”

Hunting dimers

“…First of all, the octahedral neutral B 6 (NR 2 ) 6 , R = Me, Et, highly stabilized neutral B 6 H 6 derivatives, are known [34][35][36]. If one replaces (mentally) two BR by C, one gets the 8B molecule.…”

Structures, Energies, and Spin–Spin Coupling Constants of Methyl-Substituted 1,3-Diborata-2,4-diphosphoniocyclobutanes: Four-member B–P–B–P Rings B2P2(CH3)nH8–n, with n = 0, 1, 2, 4

“…To do this, we removed the large substituents ( iso -propyl, tert -butyl, adamantly, etc. ), which are essential for stabilizing the B–P–B–P rings (called the corset effect ) and replaced them with fluorine atoms. This allowed us to investigate fluorine-substituent effects on the structures, relative stabilities, and spin–spin coupling constants of four-member B–P–B–P rings in molecules B 2 P 2 F n H 8– n , for n = 0, 1, 2, and 4 .…”