Coordination Modes for the Thiocyanate Ion

According to the MO calculation by Wagner,the pi-electron structure of the thiocyanate ion may be represented as  

The difference in the charge densities on the N and S atoms is not very large. This may be the reason why the NCS anion exhibits a variety of coordination modes as shown in Fig. 33. There are a large number of metal complexes containing an N-bonded or S-bonded thiocyanate ion as a unidentate ligand. Various factors influencing the relative stabilities of these two bonding modes will be discussed in Section 4.3. 

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