Tert-Butyl isocyanide

Chembox new
ImageFile = tert-butylisocyanide.png ImageSize = 120px
Name = "tert"-Butyl isocyanide
OtherNames = t-BuNC, propane, 2-isocyano-2-methyl
Section1 = Chembox Identifiers
CASNo = 7188-38-7
Section2 = Chembox Properties
Formula = C₅H₉N
MolarMass = 83.13 g/mol
Appearance = Colorless liquid
Density = 0.735 g/cm³, liquid
Solubility = N/A
MeltingPt = ? °C
BoilingPt = 91 °C

"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. [Malatesta, L. "Isocyanide Complexes of Metals"Progress in Inorganic Chemistry, 1959, volume 1, 284-291.]

"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. [OrgSynth | author = Gokel, G.W.; Widera, R.P.; Weber, W.P. | title = Phase-transfer Hofmann carbylamine reaction: tert-butyl isocyanide| collvol = 6 | collvolpages = 232| year = 1988 | prep = CV6P0232] :Me₃CNH₂ + CHCl₃ + 3 NaOH → Me₃CNC + 3 NaCl + 3 H₂O

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). [Rettig, M.F.; Maitlis, P.M. Tetrakis (tert-butyl isocyanide)D-μ-chloro-dipalladium. "Inorganic Syntheses", 1990, 28, 110-113. ISBN 0-470-13259-0.] : Pd(dba)₂ + PdCl₂(C₆H₅CN)₂ + 4 t-BuNC → PdCl₂(t-BuNC)₄ + 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. [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]

imilarity 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. [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.] 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. [Bassett, J.M.; Farrugia, L.J.; Stone, G.A. "Protonation of pentakis(t-butyl isocyanide)iron" "J.C.S. Dalton", 1980, 1789-1790.]

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. 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.]

afety

In keeping with its similarity to carbon monoxide, "tert"-butyl isocyanide is toxic.

References