An Unprecedented Charge Transfer Induced Spin Transition in an Fe–Os Cluster

High 'n low: The novel {[Fe(tmphen)2]3[Os(CN)6]2} complex (see structure) is the first example of a cluster in which a high-spin FeIII ion is in a coordination environment of four imine nitrogen atoms and two N-coordinated cyanides. Magnetic studies reveal an unprecedented type of reversible charge transfer induced spin transition (CTIST) between the low-spin FeIINCOsIII and high-spin FeIIINCOsII systems.