Specific formation of isocyanide iron complexes by reaction of primary carbamoyl ferrates with oxalylchloride

Reaction of primary carbamoyl ferrates {(CO)4Fe[C(O)NHR]}− (R=Me, Et, allyl, decyl, cyclohexyl, t-butyl, benzyl, phenyl) with 1/2 equiv. of oxalylchloride affords cis-bis-carbamoyl intermediates: (CO)4Fe[C(O)NHR]2 which thermally give rise, in good yields, to the mono-isocyanide complexes (CO)4Fe(CNR). The mechanism of the reaction is discussed. Via a similar process, an alkoxycarbamoyl intermediate (CO)4Fe[C(O)NHR](CO2Me) affords Fe(CO)5 and 1,3-dialkylurea.