Density Functional Theory Study of N–CN and O–CN Bond Cleavage by an Iron Silyl Complex

Abstract

Using hybrid density functional theory calculations with the B3LYP functional, the reaction mechanisms for cleavage of R2N–CN (R ═ H, Me) and MeO–CN bonds in the presence of an unsaturated iron(II) silyl complex, CpFe(CO)SiMe3, were studied. The following sequence of reactions was shown to be favorable: (i) coordination of a nitrile through the lone pair of electrons on the nitrile N atom (NCN) to form an end-on complex, (ii) isomerization of the end-on complex to a side-on complex, (iii) migration of the silyl group to NCN facilitated by the hypervalent character of the Si atom and its electrostatic attraction with NCN to form a stable Fe–C–NCN three-membered-ring intermediate with an Fe–NCN dative bond, (iv) dissociation of the NCN atom from Fe and coordination of an amino N atom (NNR2) or methoxy O atom to Fe leading to an Fe–C–NNR2 or Fe–C–O three-membered-ring intermediate, and (v) cleavage of the R2N–C or MeO–C bond to form a silyl isocyanide ligand. Step iv possesses the largest activation energy i...