Acyl isocyanide, chromium complexes

ORGANOMETALLIC COMPLEXES OF ISOMERIC ACYL ISOCYANIDES CHROMIUM CARBONYL (ACYL ISOCYANIDE) AND (ACYL CYANIDE) COMPLEXES... 

Among the types of complexes found here are formyl, acyl, alkyl, and aryl carbonyls, carbonyl cyanides," " carbonyl isocyanides and acetylides," and thiocarbonyl and seleno-carbonyl complexes." Of the greatest significance, however, are the chromium carbenes, for example, (CO)sCr=C(OR)R". This chemistry has been thoroughly reviewed " nevertheless, these compounds will be briefly discussed here. 

The nitrogen atom in a-ferrocenylalkylamines generally shows the same reaction pattern as that in other amines alkylation and acylation do not provide synthetic problems. Due to the high stability of the a-ferrocenylalkyl carbocations, ammonium salts readily lose amine and are, therefore, important synthetic intermediates. Acylation of primary amines with esters of formic acid gives the formamides, which can be dehydrated to isocyanides by the standard POClj/diisopropylamine technique (Fig. 4-16) [92]. Chiral isocyanides are obtained from chiral amines without any racemization during the reaction sequence. The isocyanides undergo normal a-addition at the isocyanide carbon, but could not be deprotonated at the a-carbon by even strong bases. This deviation from the normal reactivity of isocyanides prompted us to study the electrochemistry of these compounds, but no abnormal redox behaviour, compared with that of other ferrocene derivatives, was detected [93]. The isocyanides form chromium pentacarbonyl complexes on treatment with Cr(CO)s(THF) (Fig. 4-16) and electrochemistry demonstrated that there is no electronic interaction between the two metal centres. 

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