Cyanides and isocyanides of first-row transition metal M(CN) (M = Sc-Zn) are investi
gated with quantumchemistry techniques, providin
g predictions for their molecular properties. A careful analysis of the competitionbetween cyanide and isocyanide isomers alon
g the transition series has been carried out. In a
greement withthe experimental observations, late transition metals (Co-Zn) clearly prefer a cyanide arran
gement. On theother hand, early transition metals (Sc-Fe), with the only exception of the Cr(CN) system, favor the isocyanideisomer. The theoretical calculations predict the followin
g unknown isocyanides, ScNC(
3![](/ima<font color=)
ges/
gifchars/Delta.
gif" BORDER=0 >), TiNC(
4![](/ima<font color=)
ges/
gifchars/Phi.
gif" BORDER=0 >), VNC(
5![](/ima<font color=)
ges/
gifchars/Delta.
gif" BORDER=0 >), and MnNC(
7![](/ima<font color=)
ges/
gifchars/Si
gma.
gif" BORDER=0 >
+), and a
gree with the experimental observation of FeNC(
6![](/ima<font color=)
ges/
gifchars/Delta.
gif" BORDER=0 >) and the CrCN(
6![](/ima<font color=)
ges/
gifchars/Si
gma.
gif" BORDER=0 >
+) cyanide.First-row transition metal cyanides and isocyanides are predicted to have relatively lar
ge dissociation ener
gieswith values within the ran
ge 80-101 kcal mol
-1, except Zn(CN), which has a dissociation ener
gy around50-55 kcal mol
-1, and low isomerization barriers. A detailed analysis of the bondin
g has been carried outemployin
g the topolo
gical analysis of the char
ge density and an ener
gy decomposition analysis. The role ofthe covalent and electrostatic contributions to the metal-li
gand bondin
g, as well as the importance of
![](/ima<font color=)
ges/
gifchars/pi.
gif" BORDER=0 >bondin
g, are discussed.