''tert''-Butyl isocyanide

tert-Butyl isocyanide

Names
Preferred IUPAC name 2-Isocyano-2-methylpropane
Other names t-BuNC
Identifiers
CAS Number	7188-38-7 Y
3D model (JSmol)	Interactive image
ChemSpider	22045 Y
ECHA InfoCard	100.027.776
PubChem CID	23577
InChI InChI=1S/C5H9N/c1-5(2,3)6-4/h1-3H3 Y Key: FAGLEPBREOXSAC-UHFFFAOYSA-N Y InChI=1/C5H9N/c1-5(2,3)6-4/h1-3H3 Key: FAGLEPBREOXSAC-UHFFFAOYAL
SMILES CC(C)(C)[N+]#[C-]
Properties
Chemical formula	C5H9N
Molar mass	83.13 g/mol
Appearance	Colorless liquid
Density	0.735 g/cm3, liquid
Boiling point	91 °C (196 °F; 364 K)
Solubility in water	N/A
Except where otherwise noted, 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

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

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

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

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

References

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. CS1 maint: Multiple names: authors list (link); Coll. Vol., 6, p. 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.