Chemistry of boranes. XVIII. A preparative separation of halogenodecaboranes. The isolation of 1-, 2-, 5-, and 6-bromotridecahydrodecaboranes

Stuchlík, J.; Heřmánek, S.; Plešek, Jaromı́r; Štı́br, Bohumil

doi:10.1135/cccc19700339

Cited by 8 publications

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“…In agreement with a previous finding that decaboranyl ethers degrade on silica gel, chromatographic separations resulted in decreased yields, especially when used to isolate 5OR , as these compounds were both less stable and had longer retention times than the 6OR isomers. If the silica gel was not acidified prior to use, complete 5OR degradation was observed during chromatography. Both 5OR and 6OR slowly degraded when left exposed to air for prolonged periods.…”

Section: Resultsmentioning

confidence: 99%

“…The 5-X-B 10 H 13 ( 5X ) and 6-X-B 10 H 13 ( 6X ) (X = F, Cl, Br, I) compounds were synthesized according to literature procedures. , All alcohols, phenols, thiols, phenylthiols, deuterated alcohols (from Aldrich) and toluene, NaHCO 3 , CH 2 Cl 2 , hexanes, pentane, CDCl 3 , and D 2 O (from Fisher) were used as received. Silica gel (Fisher) was acidified according to the literature method prior to use …”

Section: Methodsmentioning

confidence: 99%

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Syntheses and Surprising Regioselectivity of 5- and 6-Substituted Decaboranyl Ethers via the Nucleophilic Attack of Alcohols on 6- and 5-Halodecaboranes

2011

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The selective syntheses of new classes of decaboranyl ethers containing a range of functional groups substituted at the B5 or B6 positions were achieved through the reaction of alcohols with halodecaboranes. The surprising regioselectivity of the reaction, where the reaction of the 6-halodecaboranes (6-X-B(10)H(13)) with alcohols yielded the 5-substituted decaboranyl ethers (5-RO-B(10)H(13)) and the reaction with 5-halodecaboranes (5-X-B(10)H(13)) gave the 6-substituted decaboranyl ethers (6-RO-B(10)H(13)), was confirmed by NMR and X-ray crystallographic analyses. The crystallographic determinations also showed that the decaboranyl ethers had shortened B-O bonds and apparent sp(2) hybridization at oxygen indicating significant π-backbonding from oxygen to the cage boron. A possible substitution mechanism was computationally identified involving: (1) initial nucleophilic attack by the alcohol-oxygen at a site adjacent to the 5- or 6-halo-substituted boron, (2) movement of the terminal hydrogen at the point of attack to a bridging position, (3) formation of a 5-membered (B-O-H-Cl-B) cyclic transition state allowing the acidic methanolic-hydrogen to bond to the halogen, (4) release of HX, and finally (5) movement of a bridging hydrogen into the vacated terminal position. Deuterium labeling studies confirmed the movement of hydrogen from a bridging position of the halodecaborane into the halogen-vacated terminal position on the decaboranyl ether product. The relative reaction rates of the 6-X-B(10)H(13) compounds (X = F, Cl, Br, I) with alcohols were likewise found to be consistent with this mechanism.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Syntheses and Surprising Regioselectivity of 5- and 6-Substituted Decaboranyl Ethers via the Nucleophilic Attack of Alcohols on 6- and 5-Halodecaboranes

2011

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“…Other solvents (Fisher) were used as received unless otherwise noted. Prior to use, silica gel (Fisher) was saturated with acetic acid vapors for 12 h in an evacuated desiccator at room temperature, followed by vacuum drying at 120 °C for 5 h. The high pressure reaction vessel (88 mL, catalog no. 110207 0003, Andrew’s Glass Company) used for the acetylene reactions was fitted with a stainless steel needle Swagelok valve (part no.…”

Section: Methodsmentioning

confidence: 99%

Iridium and Ruthenium Catalyzed Syntheses, Hydroborations, and Metathesis Reactions of Alkenyl-Decaboranes

2013

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The selective syntheses of new classes of 6,9-dialkenyl- and 6-alkenyl-decaboranes and 6-alkyl-9-alkenyl-decaboranes have been achieved via iridium and ruthenium catalyzed decaborane and 6-alkyl-decaborane alkyne-hydroborations. Reactions employing [Cp*IrCl2]2 and [RuCl2(p-cymene)]2 precatalysts gave β-E-alkenyl-decaboranes, while the corresponding reactions with [RuI2(p-cymene)]2 gave the α-alkenyl-decaborane isomers, with the differences in product selectivity suggesting quite different mechanistic steps for the catalysts. The alkenyl-decaboranes were easily converted to other useful derivatives, including coupled-cage and functionally substituted compounds, via iridium-catalyzed hydroborations and ruthenium-catalyzed homo and cross olefin-metathesis reactions.

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“…All other solvents were used as received unless noted otherwise. Silica gel (Fisher) was pretreated with acetic acid vapors and dried in vacuo as described elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…Separation of the minor 5-X-B 10 H 13 products in these mixtures was then achieved by preparative thin layer chromatography, but isolated yields of the pure products were not reported . An earlier paper reported 5Br yields of ∼30% following column chromatographic separation of a 43:57 ratio 5Br / 6Br mixture generated using the same HBr reaction . The reaction of 6,9-(Me 2 S) 2 -B 10 H 12 with HI gave a much more favorable, 63:37, 5I / 6I ratio, but with only a low 16% total yield of the monoiododecaborane mixture .…”

Section: Introductionmentioning

confidence: 99%

Efficient Syntheses of 5-X-B₁₀H₁₃ Halodecaboranes via the Photochemical (X = I) and/or Base-Catalyzed (X = Cl, Br, I) Isomerization Reactions of 6-X-B₁₀H₁₃

2010

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High yield syntheses of the 5-X-B(10)H(13) (5X) halodecaboranes have been achieved through the photochemical (X = I) or base-catalyzed (X = Cl, Br, I) isomerization reactions of their 6-X-B(10)H(13) (6X) isomers. 5I was obtained in 80% isolated yield upon the UV photolysis of 6I. Treatment of 6X (X = Cl, Br, I) with catalytic amounts of triethylamine at 60 degrees C led to the formation of 78:22 (Cl), 82:18 (Br), and 86:14 (I) ratio 5X/6X equilibrium mixtures. The 5X isomers were then separated from these mixtures by selective crystallization (Br and I) or column chromatography (Cl), with the supernatant mixtures in each case then subjected to another round of isomerization/separation to harvest a second crop of 5X. The combined isolated yields of pure products after two cycles were 71% 5-Cl-B(10)H(13), 83% 5-Br-B(10)H(13), and 68% 5-I-B(10)H(13). The previously proposed structures of 5-Br-B(10)H(13) and 5-I-B(10)H(13) were crystallographically confirmed. Deprotonation of 6X and 5X with 1,8-bis(dimethylamino)naphthalene (PS) resulted in the formation of [PSH(+)][6X(-)] and [PSH(+)][5X(-)]. Density functional theory-gauge-independent atomic orbital (DFT/GIAO) calculations and crystallographic determinations of [PSH(+)][6Cl(-)] and [PSH(+)][6Cl(-)] confirmed bridge-deprotonation at a site adjacent to the halogen-substituted borons. NMR studies of the 6-Br-B(10)H(13) isomerization induced by stoichiometric amounts of PS showed that following initial deprotonation to form 6-Br-B(10)H(12)(-), isomerization occurred at 60 degrees C to form an equilibrium mixture of 6-Br-B(10)H(12)(-) and 5-Br-B(10)H(12)(-). DFT calculations also showed that the observed 5-X-B(10)H(13)/6-X-B(10)H(13) equilibrium ratios in the triethylamine-catalyzed reactions were consistent with the energetic differences of the 5-X-B(10)H(12)(-) and 6-X-B(10)H(12)(-) anions. These results strongly support a mechanistic pathway for the base-catalyzed 6X to 5X conversions involving the formation and subsequent isomerizations of the 6X(-) anions. While triethylamine did not catalyze the isomerization reactions of either 6-(C(6)H(13))-B(10)H(13) or 6,9-(C(6)H(13))(2)-B(10)H(12), it catalyzed the isomerization of 6-X-9-(C(6)H(13))-B(10)H(12) to 5-X-9-(C(6)H(13))-B(10)H(12) resulting from halo, but not alkyl rearrangement. Comparisons of the chemical shift values found in the temperature-dependent (11)B NMR spectra of 6Cl(-) and 6F(-) with DFT/GIAO chemical shift calculations indicate the fluxional behavior observed for these anions results from a process involving hydrogen migration around the open face that leads to the averaging of some boron resonances at higher temperatures.

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Chemistry of boranes. XVIII. A preparative separation of halogenodecaboranes. The isolation of 1-, 2-, 5-, and 6-bromotridecahydrodecaboranes

Cited by 8 publications

References 0 publications

Syntheses and Surprising Regioselectivity of 5- and 6-Substituted Decaboranyl Ethers via the Nucleophilic Attack of Alcohols on 6- and 5-Halodecaboranes

Syntheses and Surprising Regioselectivity of 5- and 6-Substituted Decaboranyl Ethers via the Nucleophilic Attack of Alcohols on 6- and 5-Halodecaboranes

Iridium and Ruthenium Catalyzed Syntheses, Hydroborations, and Metathesis Reactions of Alkenyl-Decaboranes

Efficient Syntheses of 5-X-B₁₀H₁₃ Halodecaboranes via the Photochemical (X = I) and/or Base-Catalyzed (X = Cl, Br, I) Isomerization Reactions of 6-X-B₁₀H₁₃

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Chemistry of boranes. XVIII. A preparative separation of halogenodecaboranes. The isolation of 1-, 2-, 5-, and 6-bromotridecahydrodecaboranes

Cited by 8 publications

References 0 publications

Syntheses and Surprising Regioselectivity of 5- and 6-Substituted Decaboranyl Ethers via the Nucleophilic Attack of Alcohols on 6- and 5-Halodecaboranes

Syntheses and Surprising Regioselectivity of 5- and 6-Substituted Decaboranyl Ethers via the Nucleophilic Attack of Alcohols on 6- and 5-Halodecaboranes

Iridium and Ruthenium Catalyzed Syntheses, Hydroborations, and Metathesis Reactions of Alkenyl-Decaboranes

Efficient Syntheses of 5-X-B10H13 Halodecaboranes via the Photochemical (X = I) and/or Base-Catalyzed (X = Cl, Br, I) Isomerization Reactions of 6-X-B10H13

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Efficient Syntheses of 5-X-B₁₀H₁₃ Halodecaboranes via the Photochemical (X = I) and/or Base-Catalyzed (X = Cl, Br, I) Isomerization Reactions of 6-X-B₁₀H₁₃