CNbindingen

CN-bindingen refers to the interaction of cyanide ligands with metal centers in coordination and organometallic chemistry. The cyanide ligand (CN−) is small and linear, and it most commonly binds through its carbon atom to a metal, creating a linear M–C≡N fragment. CN− can also bind through nitrogen or form bridging modes between two or more metal centers; carbon coordination is far more common because of the ligand’s strong π-acceptor character.

Binding modes and characteristics: In most complexes CN− binds terminally via carbon, giving a straightforward M–C≡N linkage. In larger clusters or extended networks, cyanide can bridge in µ-C, µ-N, or µ-C,N fashion. Cyanide is regarded as a strong-field ligand in the spectrochemical series, often promoting low-spin configurations in octahedral complexes. The cyanide ligand is short and highly directional, and backbonding from metal d orbitals affects both the M–C and C≡N bonds. The C–N bond in the cyanide moiety remains close to a triple-bond character, though its bond order can be influenced by coordination. Infrared spectroscopy commonly detects the CN stretching vibration, typically in the high 2000 cm−1 region, with shifts depending on the metal and binding mode.

Notable examples and significance: Hexacyanometalate anions, such as [Fe(CN)6]4− (ferrocyanide) and [Fe(CN)6]3− (ferricyanide), are foundational in bonding chemistry and electrochemistry. Prussian blue-type materials are extended cyanide-bridged networks that have applications in catalysis, sensing, and energy storage. CN− ligands also play a role in biological contexts as strong metal binders, which underpins both their toxicity and their use in detoxification research.

Overall, CN-bindingen describes a central concept in inorganic chemistry, illustrating how a small, linear ligand can govern structure, electronic properties, and applications of metal complexes.