Aromatische Borane mit planar-tetrakoordinierten Boratomen und sehr kurzen B-B-Abständen

Präsang, Carsten; Hofmann, Matthias; Geiseler, Gertraud; Massa, Werner; Berndt, A.

doi:10.1002/1521-3757(20020503)114:9<1597::aid-ange1597>3.0.co;2-z

Cited by 37 publications

(21 citation statements)

References 22 publications

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“…In an attempt to dehalogenate a 1:1 mixture of Me 2 NBCl 2 and Me 2 N(Cl)B-B(Cl)NMe 2 to obtain the corresponding cyclo-triborane(3) and cyclo-pentaborane(5), we isolated colorless crystals of the composition (BNMe 2 ) 6 , which exhibited three 11 tetrabora-bicyclo-butane structure. However, the four boron atoms of the B 4 frame supply only eight electrons, therefore, the bonding requires the presence of nonclassical bonds.…”

Section: Cyclo-boranes and Polyhedral-boranesmentioning

confidence: 99%

“…In 4a, there are eight framework electrons (6σ + 2π FEs), but only six in the tetraborane(6) 15a [6] (4σ + 2π FEs), because 2σ electrons are needed to bind the two additional H atoms. These form two 3c,2e σ bonds (shown as triangular dashed lines) and one 4c,2e π bond (ellipsoid).…”

Section: Cyclo-boranes and Polyhedral-boranesmentioning

confidence: 99%

“…The mechanism is proposed by Berndt et al [6], who showed that the dehalogenation of 16a with lithium naphthalenide in THF leads to 4a in 40-50 % yield.…”

Section: Cyclo-boranes and Polyhedral-boranesmentioning

confidence: 99%

“…The planar cyclo-tetraborane(4) 1, which has not been unambiguously characterized to date [1,2], stabilizes itself by folding along a diagonal to give 2, and an extension of this folding could finally lead to tetraboratetrahedranes 3 (R = Cl [3], CMe 3 [4]). The extend of folding is controlled by electronic and/or steric properties of R. Substituents with different donor/acceptor capabilities (R, R′) may cause the formation of a planar bicyclo-tetraborane 4 [R = NMe 2 , R′ = B(NMe 2 ) 2 ] [5,6] having the familiar diamond shape of two adjacent deltahedral faces found in polyhedral boranes and carboranes. One can regard 4 as the smallest polydeltahedron, the dihedron.…”

Section: Introductionmentioning

confidence: 99%

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Small boranes, carboranes, and heterocarboranes

Siebert

Maier

et al. 2003

Pure and Applied Chemistry

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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.

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Section: Cyclo-boranes and Polyhedral-boranesmentioning

confidence: 99%

Section: Cyclo-boranes and Polyhedral-boranesmentioning

confidence: 99%

“…The mechanism is proposed by Berndt et al [6], who showed that the dehalogenation of 16a with lithium naphthalenide in THF leads to 4a in 40-50 % yield.…”

Section: Cyclo-boranes and Polyhedral-boranesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Small boranes, carboranes, and heterocarboranes

Siebert

Maier

et al. 2003

Pure and Applied Chemistry

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“…The isoelectronic 2u [7] was computed in 1995 to be lower in energy than the classical 2u* by not less than 54.9 kcal/mol. As a first experimental approach to compounds of type 2, the boryl-bridged 2a was obtained recently by addition of 4-t-butylpyridine to the first repre-sentative of two-electron aromatic tetraboranes(6) with nonclassical σ-bonds, 3 [10]. A first derivative of the corresponding two-electron aromatic tetraborane(4) 4 was also presented [11].…”

Section: Introductionmentioning

confidence: 99%

Two-electron aromatics containing three and four adjacent boron atoms

Präsang

Młodzianowska

Geiseler

et al. 2003

Pure and Applied Chemistry

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A two-electron aromatic bis(tris-trimethylsilylmethylene)-substituted tetraborane(4) was found to be a useful precursor for the synthesis of two-electron aromatic tetraboranes(6), triboracyclopropanates, as well as tetraboranes(6) distorted toward triboracyclopropanates with boryl bridges. Bishomo two-electron aromatics with a borata bridge and a protonated borata bridge, respectively, are also presented.

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