Beiträge zur chemie des bors

Männig, Detlef; Nöth, Heinrich; Prigge, H.; Rotsch, A.-R.; Gopínathan, Sarada; Wilson, John W.

doi:10.1016/s0022-328x(00)99655-4

Cited by 25 publications

(9 citation statements)

References 31 publications

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“…The geometry at the boron atom is distorted trigonal planar. The B−C bond lengths (Table ) with values of 1.556(7), 1.573(6), and 1.575(7) Å are typical for B−C aryl bonds found in other three-coordinate aryl boranes (e.g., 1.589(5) and 1.571(3) Å in Ph 3 B, 1.574(4) and 1.565(7) Å in [2,6-(MeO) 2 C 6 H 3 ] 3 B, and 1.579(2) and 1.580(3) Å in Mes 3 B 13 ) and 9-borafluorenes (e.g., 1.592(6) and 1.588(6) Å in 9- N , N -(di- tert -butylboryl)methyl-9-borafluorene and 1.556(4) and 1.549(3) Å in 9-pentafluorophenyloctafluoro-9-borafluorene). Due to the 9-borafluorene structure constraints, the internal C(9)−B(1)−C(16) angle with a value of 103.5(4)° is significantly smaller than the other two C−B−C angles with values of 128.3(4)° and 127.9(4)°.…”

Section: Resultsmentioning

confidence: 86%

Unsymmetrical 9-Borafluorenes via Low-Temperature C−H Activation of m-Terphenylboranes

2002

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The reaction of 2,6-(4-t-BuC6H4)2C6H3Li and with H2ClB·SMe2 or HCl2B·SMe2 in hexane solution afforded the m-terphenyl-substituted unsymmetrical 9-borafluorene 1-(4-tert-butylphenyl)-7-tert-butyl-9-(bis-2,6-(4-tert-butylphenyl)phenyl)-9-borafluorene, 1, in good to moderate yields. The related reaction of 2,6-(3,5-Me2C6H3)2C6H3Li with BH2Cl·SMe2 or BHCl2·SMe2 in toluene solution gave 1-(3,5-dimethylphenyl)-6,8-dimethyl-9-(bis-2,6-(3,5-dimethylphenyl)phenyl)-9-borafluorene, 3. Compounds 1 and 3 are air-stable fluorescent solids. The reactions of 2,6-(2-MeC6H4)2C6H3Li or 2,6-Mes2C6H3Li (which possess either two or no o- and o‘ ‘-hydrogens) with H2ClB·SMe2 gave the primary boranes [2,6-(2-MeC6H4)2C6H3BH2]2, 4, and [2,6-Mes2C6H3BH2]2, 5, respectively. Quenching of the reaction of 2,6-(4-t-BuC6H4)2C6H3Li with H2ClB·SMe2 after 1.5 h with pyridine resulted in the isolation of the primary borane [2,6-(4-t-BuC6H4)2C6H3BH2]2, 2, as the pyridine adduct 2·py, which after thermolysis at 190 °C gave 1-(4-tert-butylphenyl)-7-tert-butyl-9-borafluorene·pyridine, 7·py. Heating a C6D6 solution of 4 to 60−70 °C led to C−H activation and formation of a 1:1 adduct of monomeric 4 and 1-(2-methylphenyl)-5-methyl-9-borafluorene, 12. Reaction of 2 equiv of 2,6-(4-t-BuC6H4)2C6H3Li with H2ClB·SMe2 in hexane solution followed by addition of THF gave the very crowded diterphenyl borate [2,6-(4-t-BuC6H4)2C6H3]2B(μ-H)2Li(THF)2]2, 11, which can be converted to 1 by simple addition of water. Prolonged exposure of 1 to concentrated aqueous HCl led to B−C bond cleavage and formation of the sterically very crowded diterphenylborinic acid [2,6-(4-t-BuC6H4)2C6H3]2BOH, 15. All compounds have been characterized by 1H, 13C, and 11B NMR spectroscopy and mass spectrometry, and compounds 1, 4, and 11 have also been characterized by single-crystal X-ray crystallography.

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Section: Resultsmentioning

confidence: 86%

Unsymmetrical 9-Borafluorenes via Low-Temperature C−H Activation of m-Terphenylboranes

2002

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“…X-ray-quality crystals of 11 were grown from pentane, and the X-ray data confirmed the formulation as the diborylamine (Figure ). The B−N bond distances in 11 average 1.419(6) Å, which is typical for B−N bond distances in diborylamines. − Location and refinement of the proton on nitrogen revealed that the geometry at N is planar, with a B−N−B angle of 132.9(3)°. This angle is similar to the corresponding angle of 135.4(2)° observed for HN(BPh 2 ) 2 …”

Section: Resultsmentioning

confidence: 93%

“…The B-N bond distances in 11 average 1.419(6) Å, which is typical for B-N bond distances in diborylamines. [45][46][47][48] Location and refinement of the proton on nitrogen revealed that the geometry at N is planar, with a B-N-B angle of 132.9(3)°. This angle is similar to the corresponding angle of 135.4(2)°observed for HN(BPh 2 ) 2 .…”

Section: Resultsmentioning

confidence: 99%

Steric Effects in Metathesis and Reduction Reactions of Phosphinimines with Catechol- and Pinacolboranes

et al. 2005

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A series of catecholboryl-phosphinimide complexes with the general formula (mu-(R(3)PN)Bcat)(x)() (cat = O(2)C(6)H(4)) have been synthesized via associative metathetical reactions. For R = Et, n-Bu, Ph, and i-Pr and R(3) = n-Bu t-Bu(2) X-ray crystallography as well as solution NMR spectroscopy and reactivity studies reveal that these species are dimeric. In the case of R = t-Bu, the steric congestion results in the monomeric species, t-Bu(3)PNBcat. Similarly, reactions of R(t-Bu)(2)PNH (R = n-Bu, t-Bu) and i-Pr(3)PNH with pinacolborane (HBO(2)C(2)Me(4) = HBpin) led to the formation of n-Bu(t-Bu(2))PNBpin, t-Bu(3)PNBpin, and i-Pr(3)PNBpin. Analogous reactions of smaller phosphinimines R(3)PNH (R = Et or n-Bu) with pinacolborane (HBpin) generated free phosphine and the boron-containing product HN(Bpin)(2). In the related reactions of R(3)PNPh or R(3)PNAd (R = Et and n-Bu) and HBpin, the white crystalline solids PhHN(Bpin) or AdHN(Bpin) were isolated. HN(Bpin)(2) was also derived from the reaction of Et(3)PNSiMe(3) and HBpin. Kinetic studies showed this reaction is first order in both reagents with a rate constant of 1.3(7) x 10(-4) s(-1). A mechanism involving a 1:1 donor-acceptor interaction of the phosphinimine and borane affording reduction of the phosphinimine to phosphine with concurrent formation of borylamine is proposed. Computational studies were performed to probe the steric effects on these reactions of phosphinimine and borane. Model reactions involving t-Bu(3)PNH showed a lower activation barrier for protonolysis in comparison to phosphinimine reduction. In contrast, for the smaller phosphinimine H(3)PNH, the activation barriers for phosphinimine reduction are lower. The causes of these steric effects are considered.

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“…Die beiden BC-Bindungen in 7a sind lang und entsprechen der langen BC-Bindung in 6a. Innerhalb des 3a-Kriteriums liegen im B 2 NC-Vierring gleich lange BN-Bindungen vor, die Diborylaminen entsprechen [18]. Sie sind im Durchschnitt etwas länger als die beiden exocyclischen BN-Bindungen, die ihrerseits etwas länger sind als in 6a.…”

Section: Molekülstrukturenunclassified

Beiträge zur Chemie des Bors, 190 [1] Synthese und Molekülstruktur von 1,2-Dihydroboreten und Azadiboretidinen / Contribution to the Chemistry of Boron, 190 [1] Synthesis and Molecular Structure of 1,2-Dihydrodiboretes and Azadiboretidines

Glaser¹,

Mayer²,

Nöth³

et al. 1988

Zeitschrift Für Naturforschung B

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Abstract [2+2]-Cycloadditions of 9-Fluorenylidentetramethylpiperidinoboranes have been studied with selected olefines, acetylenes and iminoboranes. No reactions with olefines were observed. While propiolic methylester reacts exclusively at the carbonyl bond producing the oxaboretane 5, alkines such as diethylamino-alkines, cyclo-octine and phenylacetylene provide access to the'1,2-dihydroboretenes 6, 3 and 2. Tetramethylpiperidinoiminoboranes make 1.2.4-azadiboretidines 7 available.6a and 7a contain a folded four-membered ring as shown by X-ray structure analysis. There is only a weak 1,3-intraannular interaction due to BN-;r-bonding of the boron atoms with their exocyclic amino group.

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Beiträge zur chemie des bors

Cited by 25 publications

References 31 publications

Unsymmetrical 9-Borafluorenes via Low-Temperature C−H Activation of m-Terphenylboranes

Unsymmetrical 9-Borafluorenes via Low-Temperature C−H Activation of m-Terphenylboranes

Steric Effects in Metathesis and Reduction Reactions of Phosphinimines with Catechol- and Pinacolboranes

Beiträge zur Chemie des Bors, 190 [1] Synthese und Molekülstruktur von 1,2-Dihydroboreten und Azadiboretidinen / Contribution to the Chemistry of Boron, 190 [1] Synthesis and Molecular Structure of 1,2-Dihydrodiboretes and Azadiboretidines

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