Oligomerization of Cyclohexylisonitrile by tBuELi2 (E = P, As)
The reaction of tBuAsLi2 with cHexNC in THF at 20 °C leads to a trimerization of the isonitrile. Crystallization from cyclohexane/diglyme gave the salt [Li4{tBuAs(CNcHex)3}2(diglyme)2] (1). In contrast to that, six molecules of cHexNC were consumed in a similar reaction with tBuPLi2 in THF at 20 °C....
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Published in | Organometallics Vol. 24; no. 5; pp. 842 - 847 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
American Chemical Society
28.02.2005
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Online Access | Get full text |
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Summary: | The reaction of tBuAsLi2 with cHexNC in THF at 20 °C leads to a trimerization of the isonitrile. Crystallization from cyclohexane/diglyme gave the salt [Li4{tBuAs(CNcHex)3}2(diglyme)2] (1). In contrast to that, six molecules of cHexNC were consumed in a similar reaction with tBuPLi2 in THF at 20 °C. Recrystallization from DME gave the salt [Li2{tBuP(CNcHex)5(CH)}(DME)2] (2). By treatment of the reaction mixture containing 2 with wet THF, the octanuclear Li+ complex [Li8(O)(cHexNC(H)NHexc)6]·THF (3) was obtained. The existence of 3 is a strong hint at the intermediate NcHex, which had reacted with the isonitrile to give the carbodiimide cHexNCNcHex. Reduction of the carbodiimide with excess tBuPLi2 is probably responsible for the formation of the anion [cHexNC(H)NcHex]- in 3. 1−3 have been characterized by NMR and IR spectroscopy as well as by X-ray analyses. According to this, 1 can be described as a vicinal dilithiated amine in which one negative charge is delocalized over a allylic C3 sequence connected to imine functions and the other negative charge is more or less localized at a nitrogen atom. This arrangement forms dimers in the solid state with a 10-membered LiNC ring. The basic structural motif in 2 is the four-membered EC4 ring already observed in 1 with two additional units of cHexNC and one CH unit, which form a five-membered N2C3 ring. In 1 and 2 the isonitrile molecules are connected to each other by head-to-head linking. 3 consists of an O-centered Li8-cube, the faces which are capped by six anions [cHexNC(H)NcHex]-. |
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Bibliography: | istex:CC6E1257ADECA1AFA010FC1873C420D21D596E06 ark:/67375/TPS-CXK671TW-P |
ISSN: | 0276-7333 1520-6041 |
DOI: | 10.1021/om0401197 |