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](CO 2Me) affords Fe(CO) 5 and 1,3-dialkylurea. The reaction of primary carbamoyl ferrates {(CO) 4Fe[C(O)NHR]} − with 1/2 equiv. of oxalylchloride affords, in good yields, mono-isocyanide iron complexes (CO) 4Fe(CNR). The reaction probably results from an hydrogen migration between the two carbamoyl ligands of the intermediate cis-(CO) 4Fe[C(O)NHR] 2 affording an hydroxy amino carbene intermediate whose further dehydration could give rise to the final isocyanide complex.