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1,1-Dimethyldiborane

April 17, 2024

1,1-Dimethyldiborane is the organoboron compound with the formula (CH3)2B(μ-H)2BH2. A pair of related 1,2-dimethyldiboranes are also known.[3] It is a colorless gas that ignites in air.

1,1-Dimethyldiborane
Names
Preferred IUPAC name
1,1-Dimethyldiborane(6)
Other names
Unsymmetrical dimethyldiborane
Identifiers
3D model (JSmol)
  • Interactive image
  • InChI=1S/C2H10B2/c1-4(2)5-3-6-4/h3H2,1-2H3[1]
    Key: KEWIJCBOFAPULG-UHFFFAOYSA-N[2]
  • C[B]1(C)[H][BH2][H]1
Properties
C2H10B2
Molar mass 55.72 g·mol−1
Appearance Colorless gas
Melting point −150.2 °C (−238.4 °F; 123.0 K)
Boiling point −4 °C (25 °F; 269 K)
Solubility in organic solvents Soluble in ether, pentane, tetrahydrofuran
Thermochemistry
-25 kcal/mol
Hazards
NFPA 704 (fire diamond)
[2]
Health (blue): no hazard codeFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
2
2
Related compounds
Related alkyl boranes
 Methyldiborane
Trimethyldiborane
Tetramethyldiborane
Trimethylborane
Diethyldiborane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N (what is YN ?)

Formation edit

The methylboranes were first prepared by H. I. Schlesinger and A. O. Walker in the 1930s.[4][5] Methylboranes are formed by the reaction of diborane and trimethylborane. This reaction produces four different substitution of methyl with hydrogen on diborane. Produced are 1-methyldiborane, 1,1-dimethyldborane, 1,1,2-trimethyldiborane, and 1,1,2,2-tetramethyldiborane.[6]

Tetramethyl lead reacts with diborane in a 1,2-dimethoxyethane solvent at room temperature to make a range of methyl substituted diboranes, ending up at trimethylborane, but including 1,1-dimethyldiborane, and trimethyldiborane. The other outputs of the reaction are hydrogen gas and lead metal.[7]

Other methods to form methyldiboranes include heating trimethylborane with hydrogen. Alternatively trimethylborane reacts with borohydride salts with in the presence of hydrogen chloride, aluminium chloride, or boron trichloride. If the borohydride is sodium borohydride, then methane is a side product. If the metal is lithium then no methane is produced.[4] dimethylchloroborane and methyldichloroborane are also produced as gaseous products.[4]

When Cp2Zr(CH3)2 reacts with borane dissolved in tetrahydrofuran, a borohydro group inserts into the zirconium carbon bond, and methyl diboranes are produced.[8]

In ether dimethylcalcium reacts with diborane to produce dimethyldiborane and calcium borohydride:[9]

Ca(CH3)2 + 2 B2H6 → Ca(BH4)2 + B2H4(CH3)2

1,2-dimethyldiborane slowly converts on standing to 1,1-dimethyldiborane.[10]

Gas chromatography can be used to determine the amounts of the methyl boranes in a mixture. The order they elute are diborane, monomethyldiborane, trimethylborane, 1,1-dimethyldiborane, 1,2-dimethyldiborane, trimethyldiborane, and finally tetramethyldiborane.[11]

Selected properties edit

1,1-Dimethyldiborane has a dipole moment of 0.87 d.[12] The predicted heat of formation for the liquid is ΔH0f=-31 kcal/mol, and for the gas -25 kcal/mol. Heat of vapourisation was measured at 5.5 kcal/mol.[13]

Reactions edit

At −78.5 °C, methyldiborane disproportionates slowly, first to diborane and 1,1-dimethyldiborane.[14] In solution methylborane is more stable against disproportionation than dimethylborane.[15][16]

2 MeB2H5 → 1,1-Me2B2H4 + B2H6, K = 2.8, Me = CH3
3 [1,1-Me2B2H4] → 2 Me3B2H3 + B2H6, K = 0.00027

Trimethyldiborane partially disproportionates over a period of hours at room temperature to yield tetramethyldiborane and 1,2-dimethyldiborane. Over a period of weeks 1,1-dimethyldiborane appears as well.[17]

Gentler oxidation of 1,1-dimethyldiborane at 80 °C yields 2,5-dimethyl-1,3,4-trioxadiboralane, a volatile liquid that contains a ring of two boron and three oxygen atoms.[18] An intermediate in this reaction is two molecules of dimethylborylhydroperoxide (CH3)2BOOH. (CAS 41557-62-5)[19] When methyldiborane is oxidised around 150 °C a similar substance methyltrioxadiboralane is produced. At the same time dimethyltrioxadiboralane and trimethylboroxine are also formed, and also hydrocarbons, diborane, hydrogen, and dimethoxyborane (dimethyl methylboronic ester).[18]

References edit

  1. ^ Jane E. Macintyre, ed. (1994-11-10). Dictionary of Organometallic Compounds. CRC Press. p. 468. ISBN 9780412430602.
  2. ^ Baker, Charles J. (2001). The Fire Fighter's Handbook of Hazardous Materials. Jones & Bartlett Learning. p. 152. ISBN 9780962705212.
  3. ^ Srebnik, Morris; Cole, Thomas E.; Brown, Herbert C. (January 1987). "Methylborane - a remarkable unhindered monoalkylborane which achieves the controlled sequential hydroboration of representative alkenes". Tetrahedron Letters. 28 (33): 3771–3774. doi:10.1016/s0040-4039(00)96380-9.
  4. ^ a b c Long, L. H.; Wallbridge, M. G. H. (1965). "646. The chemistry of boron. Part VI. New preparative methods and decomposition studies relating to methyldiboranes". Journal of the Chemical Society (Resumed): 3513–3520. doi:10.1039/JR9650003513. (subscription required)
  5. ^ Schlesinger, H. I.; Walker, A. O. (April 1935). "Hydrides of Boron. IV. The Methyl Derivatives of Diborane". Journal of the American Chemical Society. 57 (4): 621–625. doi:10.1021/ja01307a009.
  6. ^ Bell, R. P.; Emeléus, H. J. (1948). "The boron hydrides and related compounds". Quarterly Reviews, Chemical Society. 2 (2): 132. doi:10.1039/QR9480200132.
  7. ^ Holliday, A.K.; N. Jessop, G. (November 1967). "The reaction of tetramethyllead with diborane". Journal of Organometallic Chemistry. 10 (2): 291–293. doi:10.1016/s0022-328x(00)93089-4.
  8. ^ Marsella, John A.; Caulton, Kenneth G. (May 1982). "Dealkylation of zirconium(IV) by borane: the intimate mechanism of an alkyl transfer reaction". Journal of the American Chemical Society. 104 (9): 2361–2365. doi:10.1021/ja00373a005.
  9. ^ James, B. D.; Wallbridge, M. G. H. (1970). "Metal Tetrahydroborates". In Lippard, Stephen J. (ed.). Progress in Inorganic Chemistry, Volume 11. Wiley. p. 185. ISBN 0471-54081-1.
  10. ^ Lehmann, Walter J.; Wilson, Charles O.; Shapiro, I. (1960). "Infrared Spectra of Alkyldiboranes. III. 1,2-Dimethyl- and 1,2-Diethyldiboranes". The Journal of Chemical Physics. 33 (2): 590. Bibcode:1960JChPh..33..590L. doi:10.1063/1.1731190.
  11. ^ Seely, G. R.; Oliver, J. P.; Ritter, D. M. (December 1959). "Gas-Liquid Chromatographic Analysis of Mixtures Containing Methyldiboranes". Analytical Chemistry. 31 (12): 1993–1995. doi:10.1021/ac60156a032.
  12. ^ Chiu, C. W.; Burg, A. B.; Beaudet, R. A. (15 March 1983). "Microwave spectrum, dipole moment, barrier to internal rotation of 1,1-dimethyldiborane". The Journal of Chemical Physics. 78 (6): 3562–3566. Bibcode:1983JChPh..78.3562C. doi:10.1063/1.445182.
  13. ^ Altschuller, Aubrey P. (4 October 1955). "Calculated Heats of Formation and Combustion of Boron Compounds (Boron, Hydrogen, Carbon, Silicon)" (PDF). NACA Research Memorandum. Cleveland, Ohio: National Advisory Committee for Aeronautics. p. 22. Retrieved 14 August 2015.
  14. ^ Bunting, Roger K. (22 Sep 2009). "55 1-Methyldiborane". In Duward F. Shriver (ed.). Inorganic Syntheses, Volume 19. John Wiley and Sons. pp. 237–238. ISBN 978-0471045427.
  15. ^ Brown, Herbert C.; Cole, Thomas E.; Srebnik, Morris; Kim, Kee Won (December 1986). "Hydroboration. 79. Preparation and properties of methylborane and dimethylborane and their characteristics as hydroborating agents. Synthesis of tertiary alcohols containing methyl groups via hydroboration". The Journal of Organic Chemistry. 51 (25): 4925–4930. doi:10.1021/jo00375a031.
  16. ^ Onak, Thomas (1 January 1966). "Carboranes and Organo-Substituted Boron Hydrides". In Stone, F. G. A.; West, Robert (eds.). Advances in Organometallic Chemistry. New York, London: Academic Press. p. 284. ISBN 9780080580043. Retrieved 19 August 2015.
  17. ^ Lehmann, Walter J.; Wilson, Charles O.; Shapiro, I. (1961). "Infrared Spectra of Alkyldiboranes. V. Tri- and Tetramethyl- and Ethyldiboranes". The Journal of Chemical Physics. 34 (3): 783. Bibcode:1961JChPh..34..783L. doi:10.1063/1.1731675.
  18. ^ a b Barton, Lawrence; Crump, John M.; Wheatley, Jeffrey B. (June 1974). "Trioxadiborolanes from the oxidation of methyldiborane". Journal of Organometallic Chemistry. 72 (1): C1–C3. doi:10.1016/s0022-328x(00)82027-6.
  19. ^ Barton, Lawrence; Crump, John M. (November 1973). "Oxidation of 1,1-dimethyldiborane. Gas-phase peroxide intermediates". Inorganic Chemistry. 12 (11): 2506–2510. doi:10.1021/ic50129a003.

April 17, 2024
dimethyldiborane, organoboron, compound, with, formula, 2bh2, pair, related, dimethyldiboranes, also, known, colorless, that, ignites, namespreferred, iupac, name, other, names, unsymmetrical, dimethyldiboraneidentifierscas, number, 16924, model, jsmol, intera. 1 1 Dimethyldiborane is the organoboron compound with the formula CH3 2B m H 2BH2 A pair of related 1 2 dimethyldiboranes are also known 3 It is a colorless gas that ignites in air 1 1 Dimethyldiborane NamesPreferred IUPAC name 1 1 Dimethyldiborane 6 Other names Unsymmetrical dimethyldiboraneIdentifiersCAS Number 16924 32 6 1 3D model JSmol Interactive imageInChI InChI 1S C2H10B2 c1 4 2 5 3 6 4 h3H2 1 2H3 1 Key KEWIJCBOFAPULG UHFFFAOYSA N 2 SMILES C B 1 C H BH2 H 1PropertiesChemical formula C 2H 10B 2Molar mass 55 72 g mol 1Appearance Colorless gasMelting point 150 2 C 238 4 F 123 0 K Boiling point 4 C 25 F 269 K Solubility in organic solvents Soluble in ether pentane tetrahydrofuranThermochemistryStd enthalpy offormation DfH 298 25 kcal molHazardsNFPA 704 fire diamond 2 22Related compoundsRelated alkyl boranes MethyldiboraneTrimethyldiboraneTetramethyldiboraneTrimethylboraneDiethyldiboraneExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N what is Y N Infobox references Contents 1 Formation 2 Selected properties 3 Reactions 4 ReferencesFormation editThe methylboranes were first prepared by H I Schlesinger and A O Walker in the 1930s 4 5 Methylboranes are formed by the reaction of diborane and trimethylborane This reaction produces four different substitution of methyl with hydrogen on diborane Produced are 1 methyldiborane 1 1 dimethyldborane 1 1 2 trimethyldiborane and 1 1 2 2 tetramethyldiborane 6 Tetramethyl lead reacts with diborane in a 1 2 dimethoxyethane solvent at room temperature to make a range of methyl substituted diboranes ending up at trimethylborane but including 1 1 dimethyldiborane and trimethyldiborane The other outputs of the reaction are hydrogen gas and lead metal 7 Other methods to form methyldiboranes include heating trimethylborane with hydrogen Alternatively trimethylborane reacts with borohydride salts with in the presence of hydrogen chloride aluminium chloride or boron trichloride If the borohydride is sodium borohydride then methane is a side product If the metal is lithium then no methane is produced 4 dimethylchloroborane and methyldichloroborane are also produced as gaseous products 4 When Cp2Zr CH3 2 reacts with borane dissolved in tetrahydrofuran a borohydro group inserts into the zirconium carbon bond and methyl diboranes are produced 8 In ether dimethylcalcium reacts with diborane to produce dimethyldiborane and calcium borohydride 9 Ca CH3 2 2 B2H6 Ca BH4 2 B2H4 CH3 21 2 dimethyldiborane slowly converts on standing to 1 1 dimethyldiborane 10 Gas chromatography can be used to determine the amounts of the methyl boranes in a mixture The order they elute are diborane monomethyldiborane trimethylborane 1 1 dimethyldiborane 1 2 dimethyldiborane trimethyldiborane and finally tetramethyldiborane 11 Selected properties edit1 1 Dimethyldiborane has a dipole moment of 0 87 d 12 The predicted heat of formation for the liquid is DH0f 31 kcal mol and for the gas 25 kcal mol Heat of vapourisation was measured at 5 5 kcal mol 13 Reactions editAt 78 5 C methyldiborane disproportionates slowly first to diborane and 1 1 dimethyldiborane 14 In solution methylborane is more stable against disproportionation than dimethylborane 15 16 2 MeB2H5 1 1 Me2B2H4 B2H6 K 2 8 Me CH3 3 1 1 Me2B2H4 2 Me3B2H3 B2H6 K 0 00027Trimethyldiborane partially disproportionates over a period of hours at room temperature to yield tetramethyldiborane and 1 2 dimethyldiborane Over a period of weeks 1 1 dimethyldiborane appears as well 17 Gentler oxidation of 1 1 dimethyldiborane at 80 C yields 2 5 dimethyl 1 3 4 trioxadiboralane a volatile liquid that contains a ring of two boron and three oxygen atoms 18 An intermediate in this reaction is two molecules of dimethylborylhydroperoxide CH3 2BOOH CAS 41557 62 5 19 When methyldiborane is oxidised around 150 C a similar substance methyltrioxadiboralane is produced At the same time dimethyltrioxadiboralane and trimethylboroxine are also formed and also hydrocarbons diborane hydrogen and dimethoxyborane dimethyl methylboronic ester 18 References edit Jane E Macintyre ed 1994 11 10 Dictionary of Organometallic Compounds CRC Press p 468 ISBN 9780412430602 Baker Charles J 2001 The Fire Fighter s Handbook of Hazardous Materials Jones amp Bartlett Learning p 152 ISBN 9780962705212 Srebnik Morris Cole Thomas E Brown Herbert C January 1987 Methylborane a remarkable unhindered monoalkylborane which achieves the controlled sequential hydroboration of representative alkenes Tetrahedron Letters 28 33 3771 3774 doi 10 1016 s0040 4039 00 96380 9 a b c Long L H Wallbridge M G H 1965 646 The chemistry of boron Part VI New preparative methods and decomposition studies relating to methyldiboranes Journal of the Chemical Society Resumed 3513 3520 doi 10 1039 JR9650003513 subscription required Schlesinger H I Walker A O April 1935 Hydrides of Boron IV The Methyl Derivatives of Diborane Journal of the American Chemical Society 57 4 621 625 doi 10 1021 ja01307a009 Bell R P Emeleus H J 1948 The boron hydrides and related compounds Quarterly Reviews Chemical Society 2 2 132 doi 10 1039 QR9480200132 Holliday A K N Jessop G November 1967 The reaction of tetramethyllead with diborane Journal of Organometallic Chemistry 10 2 291 293 doi 10 1016 s0022 328x 00 93089 4 Marsella John A Caulton Kenneth G May 1982 Dealkylation of zirconium IV by borane the intimate mechanism of an alkyl transfer reaction Journal of the American Chemical Society 104 9 2361 2365 doi 10 1021 ja00373a005 James B D Wallbridge M G H 1970 Metal Tetrahydroborates In Lippard Stephen J ed Progress in Inorganic Chemistry Volume 11 Wiley p 185 ISBN 0471 54081 1 Lehmann Walter J Wilson Charles O Shapiro I 1960 Infrared Spectra of Alkyldiboranes III 1 2 Dimethyl and 1 2 Diethyldiboranes The Journal of Chemical Physics 33 2 590 Bibcode 1960JChPh 33 590L doi 10 1063 1 1731190 Seely G R Oliver J P Ritter D M December 1959 Gas Liquid Chromatographic Analysis of Mixtures Containing Methyldiboranes Analytical Chemistry 31 12 1993 1995 doi 10 1021 ac60156a032 Chiu C W Burg A B Beaudet R A 15 March 1983 Microwave spectrum dipole moment barrier to internal rotation of 1 1 dimethyldiborane The Journal of Chemical Physics 78 6 3562 3566 Bibcode 1983JChPh 78 3562C doi 10 1063 1 445182 Altschuller Aubrey P 4 October 1955 Calculated Heats of Formation and Combustion of Boron Compounds Boron Hydrogen Carbon Silicon PDF NACA Research Memorandum Cleveland Ohio National Advisory Committee for Aeronautics p 22 Retrieved 14 August 2015 Bunting Roger K 22 Sep 2009 55 1 Methyldiborane In Duward F Shriver ed Inorganic Syntheses Volume 19 John Wiley and Sons pp 237 238 ISBN 978 0471045427 Brown Herbert C Cole Thomas E Srebnik Morris Kim Kee Won December 1986 Hydroboration 79 Preparation and properties of methylborane and dimethylborane and their characteristics as hydroborating agents Synthesis of tertiary alcohols containing methyl groups via hydroboration The Journal of Organic Chemistry 51 25 4925 4930 doi 10 1021 jo00375a031 Onak Thomas 1 January 1966 Carboranes and Organo Substituted Boron Hydrides In Stone F G A West Robert eds Advances in Organometallic Chemistry New York London Academic Press p 284 ISBN 9780080580043 Retrieved 19 August 2015 Lehmann Walter J Wilson Charles O Shapiro I 1961 Infrared Spectra of Alkyldiboranes V Tri and Tetramethyl and Ethyldiboranes The Journal of Chemical Physics 34 3 783 Bibcode 1961JChPh 34 783L doi 10 1063 1 1731675 a b Barton Lawrence Crump John M Wheatley Jeffrey B June 1974 Trioxadiborolanes from the oxidation of methyldiborane Journal of Organometallic Chemistry 72 1 C1 C3 doi 10 1016 s0022 328x 00 82027 6 Barton Lawrence Crump John M November 1973 Oxidation of 1 1 dimethyldiborane Gas phase peroxide intermediates Inorganic Chemistry 12 11 2506 2510 doi 10 1021 ic50129a003 Retrieved from https en wikipedia org w index php title 1 1 Dimethyldiborane amp oldid 1194903276, wikipedia, wiki, book, books, library,

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