Iminoborane

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Iminoborane
Iminoborane-dimensions-IR-1987-2D.png
Iminoborane (parent compound)
Names
Other names
Boraneimine
Identifiers
3D model (JSmol)
PubChem CID
  • R,R'=H:InChI=1S/BH2N/c1-2/h1-2H
    Key: LNLSXDSWJBUPHM-UHFFFAOYSA-N
  • R,R'=H:B=N
Properties
BH2N
Molar mass 26.83 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Structure of tBuN=B-tBu (tBu = tert-butyl). The B-N bond distance is 126 pm. TBuN=B-tBu (CETSUP).png
Structure of tBuN=B-tBu (tBu = tert-butyl). The B-N bond distance is 126 pm.

Iminoboranes comprise a group of organoboron compounds with the formula RB=NR'. They are electronically related to acetylenes but are usually more reactive due to the polarity. [2] [3]

Contents

Structure and bonding

The parent iminoborane, HB=NH, is produced by the photolysis of H3BNH3. [4] [5] [6] Bonding in iminoboranes can be described by two resonance structures: [7]

The stability is dramatically affected by bulky substituents. One isolable iminoborane is (CH3)3C−B−≡N+−C(CH3)3. [1]

Comparison of bond lengths in simple boron-nitrogen hydrides
Molecule Ammonia borane [8] Aminoborane [9] Iminoborane [10]
FormulaBNH6BNH4BNH2
Class amine-borane aminoborane iminoborane
Analogous hydrocarbon ethane ethylene acetylene
Analogous hydrocarbon class alkane alkene alkyne
Structure Ammonia-borane-dimensions-MW-1983-2D.png Aminoborane-dimensions-MW-1987-2D.png Iminoborane-dimensions-IR-1987-2D.png
Ball-and-stick model Ammonia-borane-from-xtal-3D-balls.png Aminoborane-from-MW-1987-double-3D-balls.png Iminoborane-from-IR-1987-triple-3D-balls.png
Hybridisation of boron and nitrogensp3sp2sp
B-N bond length1.658 Å1.391 Å1.238 Å
Proportion of B-N single bond100%84%75%
B-H bond length1.216 Å1.195 Å
N-H bond length1.014 Å1.004 Å
Structure determination method microwave spectroscopy microwave spectroscopy infrared spectroscopy

Synthesis

Elimination of fluoro- or chlorosilanes provides a well-tested route. Bulky substituents such as (Me3Si)3Si stabilize the iminoborane with respect to oligomerization: [11]

(Me3Si)3SiB(F)-N(SiMe3)2→ (Me3Si)3Si-B=N-SiMe3 + F-SiMe3

Thermal decomposition of azidoboranes induces migration of R from boron to the nascent nitrene gives iminoboranes: [12]

R2B-N3→ RB=NR + N2

Reactivity

Oligomerization

Iminoboranes tend to oligomerize, often forming cyclic derivatives. Preventing this reaction is the purpose of bulky substituents. Five types of oligomerization product are produced: cyclodimers (1,3-diaza-2,4-diboretidines, [1] Di [13] ), cyclotrimers (borazines, Tr), bicyclotrimers (Dewar borazines, Tr′ [14] ), cyclotetramers (octahydro-1,3,5,7-tetraza-2,4,6,8-tetraborocines, Te [15] ), and polymers (polyiminoboranes, Po); which are shown below. [16] Which product is dominant depends on the structures of reactants and the reaction conditions. Some of the products can be interconverted. [17]

Figure product of iminboboranes oligomerization-1.png

Addition reactions

The addition of protic agents is fast and quantitive. [18] Boration reaction of iminoboranes is the addition of B-X single bond to B≡N, where -X can be -Cl (chloro-boration), -N3 (azido-boration), -SR (thio-boration), -NR2 (amino-boration) and R (alkyl-boration). One of these reactions are illustrated here.

Chloro-boration of iminoborane.png

Some electron-rich iminoboranes form adducts with Lewis acids. [19]

Lewis acid addition of iminoboranes.png

Cycloaddition

The typical [2+3]-cycloaddition is the addition of B≡N and RN3 to give a BN4 ring. [1] One of the widely investigated [2+2]-cycloadditions is the reaction of aldehydes and ketones.

Coordination to transition metals

Like alkynes, iminoboranes bind transition metals.

Coordination of iminoboranes to metals.png

References

  1. 1 2 3 4 Paetzold, Peter; Plotho, Christoph Von; Schmid, Günter; Boese, Roland; Schrader, Bernhard; Bougeard, Daniel; Pfeiffer, Uwe; Gleiter, Rolf; Schüfer, Wolfgang (1984). "Darstellung, Reaktionen und Struktur vontert-Butyl(tert-butylimino)boran". Chemische Berichte. 117 (3): 1089–1102. doi:10.1002/cber.19841170324.
  2. ↑ Inorganic ring systems : 7th International symposium : Papers. Chivers, Tristram. Gordon and Breach Science Publishers. 1994. ISBN   978-2-88449-168-6. OCLC   81135356.{{cite book}}: CS1 maint: others (link)
  3. ↑ Paetzold, Peter (1987). Iminoboranes. Advances in Inorganic Chemistry. Vol. 31. pp.  123–170. doi:10.1016/s0898-8838(08)60223-8. ISBN   978-0-12-023631-2.
  4. ↑ Lory, Earl R.; Porter, Richard F. (1973-03-01). "Infrared studies of matrix isolated species in the hydrogen-boron-nitrogen system". Journal of the American Chemical Society. 95 (6): 1766–1770. Bibcode:1973JAChS..95.1766L. doi:10.1021/ja00787a012. ISSN   0002-7863.
  5. ↑ Paetzold, Peter; Richter, Anette; Thijssen, Theo; Würtenberg, Stefan (1979-12-01). "Bildung, Struktur und Reaktivität von (Pentafluorphenyl)bor-tert-butylimid und seinem Cyclodimeren". Chemische Berichte. 112 (12): 3811–3827. doi:10.1002/cber.19791121207. ISSN   1099-0682.
  6. ↑ Paetzold, Peter; von Plotho, Christoph (1982-08-01). "Über weitere monomere Borimide und ihre Reaktionen". Chemische Berichte. 115 (8): 2819–2825. doi:10.1002/cber.19821150813. ISSN   1099-0682.
  7. ↑ Mó, Otilia; Yáñez, Manuel; Pendás, Angel Martín; Bene, Janet E. Del; Alkorta, Ibon; Elguero, José (2007-07-23). "Unusual substituent effects on the bonding of iminoboranes" . Phys. Chem. Chem. Phys. 9 (30): 3970–3977. Bibcode:2007PCCP....9.3970M. doi:10.1039/b702480k. hdl:10261/72489. ISSN   1463-9084. PMID   17646885.
  8. ↑ Thorne, L. R.; Suenram, R. D.; Lovas, F. J. (1983). "Microwave spectrum, torsional barrier, and structure of BH3NH3". J. Chem. Phys. 78 (1): 167–171. Bibcode:1983JChPh..78..167T. doi:10.1063/1.444528.
  9. ↑ Sugie, Masaaki; Takeo, Harutoshi; Matsumura, Chi (1987). "Microwave spectrum and molecular structure of aminoborane, BH2NH2". J. Mol. Spectrosc. 123 (2): 286–292. Bibcode:1987JMoSp.123..286S. doi:10.1016/0022-2852(87)90279-7.
  10. ↑ Kawashima, Yoshiyuki (1987). "Detection of HBNH by infrared diode laser spectroscopy". J. Chem. Phys. 87 (11): 6331–6333. Bibcode:1987JChPh..87.6331K. doi:10.1063/1.453462.
  11. ↑ Haase, Martin; Klingebiel, Uwe (1985-04-01). "Simple Synthesis of Stable Iminoboranes". Angewandte Chemie International Edition in English. 24 (4): 324. doi:10.1002/anie.198503241. ISSN   1521-3773.
  12. ↑ Paetzold, Peter; Eleftheriadis, Eleftherios; Minkwitz, Rolf; Wölfel, Volker; Gleiter, Rolf; Bischof, Peter; Friedrich, Gert (1988-01-01). "Bildung, Struktur und Reaktionen von Methyl(methylimino)boran". Chemische Berichte. 121 (1): 61–66. doi:10.1002/cber.19881210110. ISSN   1099-0682.
  13. ↑ Hess, H. (1969-11-15). "Strukturbestimmungen an Bor–Stickstoff-Verbindungen. IV. Die Kristall- und Molekularstruktur von Hexakis(trimethylsilyl)-2,4-diamino-1,3,2,4-diazadiboretidin" (PDF). Acta Crystallographica Section B (in German). 25 (11): 2342–2349. Bibcode:1969AcCrB..25.2342H. doi:10.1107/s056774086900567x. ISSN   0567-7408.
  14. ↑ Steuer, Holger-A.; Meller, Anton; Elter, Gernot (1985). "B-t-butyl-borazine und -diazadiboretidine". Journal of Organometallic Chemistry (in German). 295 (1): 1–6. doi:10.1016/0022-328x(85)88065-7.
  15. ↑ Turner H. S. and Warne R. J. 1962 Proc. Chem. Soc. 69.
  16. ↑ Advances in inorganic chemistry. Volume 31 . Emeléus, H. J. (Harry Julius), Sharpe, A. G. New York: Academic Press. 1987. ISBN   978-0-12-023631-2. OCLC   277086713.{{cite book}}: CS1 maint: others (link)
  17. ↑ Maier.G. (1978). "Tetra-tert-butyltetrahedrane". Angew. Chem. Int. Ed. Engl. 17 (7): 520–521. doi:10.1002/anie.197805201.
  18. ↑ Nöth, Heinrich; Weber, Siegfried (1985-05-01). "Beiträge zur Chemie des Bors, 154. Addition von Trimethylsily-Verbindungen und von anderen Elektrophilen an (tert-Butylimino) (tetramethylpiperidino)boran". Chemische Berichte. 118 (5): 2144–2146. doi:10.1002/cber.19851180536. ISSN   1099-0682.
  19. ↑ Nöth, Heinrich; Weber, Siegfried (1985-06-01). "Beiträge zur Chemie des Bors, 158. Addukte von Aluminium- und Galliumhalogeniden an ein Aminoiminoboran". Chemische Berichte. 118 (6): 2554–2556. doi:10.1002/cber.19851180631. ISSN   1099-0682.
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