tert-Butyl isocyanide

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tert-Butyl isocyanide
Tert-butylisocyanide.png Tert-Butyl-isocyanide 3d structure.png
Identifiers
CAS number 7188-38-7 YesY
PubChem 23577
ChemSpider 22045 YesY
Jmol-3D images Image 1
Properties
Molecular formula C5H9N
Molar mass 83.13 g/mol
Appearance Colorless liquid
Density 0.735 g/cm³, liquid
Melting point  ? °C
Boiling point 91 °C
Solubility in water N/A
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

tert-Butyl isocyanide is an organic compound with the formula Me3CNC (Me = methyl, CH3). It is an isocyanide, commonly called isonitrile or carbylamine, as defined by the functional group C≡N-R. tert-Butyl isocyanide, like most alkyl isocyanides, is a reactive colorless liquid with an extremely unpleasant odor. It forms stable complexes with transition metals and can insert into metal-carbon bonds.[1]

tert-Butyl isocyanide is prepared by a Hofmann carbylamine reaction. In this conversion, a dichloromethane solution of tert-butylamine is treated with chloroform and aqueous sodium hydroxide in the presence of catalytic amount of the phase transfer catalyst benzyltriethylammonium chloride.[2]

Me3CNH2 + CHCl3 + 3 NaOH → Me3CNC + 3 NaCl + 3 H2O

tert-Butyl isocyanide is isomeric with pivalonitrile, also known as tert-butyl cyanide. The difference, as with all carbylamine analogs of nitriles, is that the bond joining the CN functional group to the parent molecule is made on the nitrogen, not the carbon.

Coordination chemistry[edit]

By virtue of the lone electron pair on carbon, isocyanides serves as ligands in coordination chemistry, especially with metals in the 0, +1, and +2 oxidation states. tert-Butyl isocyanide has been shown to stabilize metals in unusual oxidation states, such as Pd(I).[3]

Pd(dba)2 + PdCl2(C6H5CN)2 + 4 t-BuNC → [(t-BuNC)2PdCl]2 + 2 dba + 2 C6H5CN

tert-Butyl isocyanide can form hepta-coordinate homoleptic complexes, despite having a large t-Bu group, which is held far away from the metal center because of the linearity of the M-C≡N-C linkages.[4]

Similarity to metal carbonyls[edit]

tert-Butyl isocycanide forms complexes that are stoichiometrically analogous to certain binary metal carbonyl complexes, such as Fe2(CO)9 and Fe2(tBuNC)9.[5] Although structurally similar, the analogous carbonyls differ in several ways, mainly because t-BuNC is a better donor ligand than CO. Thus, Fe(tBuNC)5 is easily protonated, whereas its counterpart Fe(CO)5 is not.[6]

Insertion into metal-carbon bonds[edit]

Under certain circumstances, tert-butyl isocyanide has been shown to insert into metal-carbon bonds to form iminoacyls. The insertion of isocyanides into metal-carbon bonds is of potential relevance in organic synthesis.[7]

Safety[edit]

Tert-butyl isocyanide is toxic. Its behavior is similar to that of its close electronic relative carbon monoxide.

References[edit]

  1. ^ Malatesta, L. Isocyanide Complexes of MetalsProgress in Inorganic Chemistry, 1959, volume 1, 284-291.
  2. ^ Gokel, G.W.; Widera, R.P.; Weber, W.P. (1988), "Phase-transfer Hofmann carbylamine reaction: tert-butyl isocyanide", Org. Synth. ; Coll. Vol. 6: 232 
  3. ^ Rettig, M.F.; Maitlis, P.M.; Cotton, F.A.; Webb, T.R. Tetrakis(tert-butyl isocyanide)Di-μ-chloro-dipalladium(I). Inorganic Syntheses, 1990, 28, 110-113. ISBN 0-470-13259-0. doi:10.1002/9780470132593.ch29
  4. ^ Carnahan, E.M.; Protasiewicz, J.D.; Lippard, S.J. 15 years of reductive coupling: what have we learned? Acc. Chem. Res. 1993, 26, 90-97
  5. ^ Bassett, J.M.; Barker, G.K.; Green, M.; Howard, J.A.; Stone, G.A.; Wolsey, W.C. "Chemistry of low-valent metal isocyanide complexes" J.C.S. Dalton, 1981, 219-227.
  6. ^ Bassett, J.M.; Farrugia, L.J.; Stone, G.A. "Protonation of pentakis(t-butyl isocyanide)iron" J.C.S. Dalton, 1980, 1789-1790.
  7. ^ Vicente, J; Abad, J.A.; Fortsch, W.; Lopez-Saez, M.J. Reactivity of ortho-palladated phenol derivatives with unsaturated molecules. Organometallics, 2004, 23, 4414-4429. DOI 10.1021/om0496131.