It is well known that IR spectroscopy is an important tool to characterize the electronic state and bridging mode of cyanide-bridged metal complexes since the cyanide stretching frequency (νCN) is quite sensitive to the oxidation state and spin state of the bridged metal centre. IR measurements carried out on 1 (Figure ) show the characteristic νCN stretches at 2145 and 2130 cm -1 , that is quite shifted from the building block