Synthesis, X-ray structure and spin crossover in the triple-decker complex [(η5-C5Me5)Cr(µ25-P5)Cr(η5-C5Me5)]+[A](A = PF6, SbF6)

Abstract
The triple-decker chromium complexes [(η5-C5Me5)Cr(µ25-P5)Cr(η5-C5Me5)]+[A](A = PF6, SbF6) can be prepared in high yield by oxidation of [(η5-C5Me5)Cr(µ25-P5)Cr(η5-C5Me5)] with either [Fe(η5-C5H5)2]+[A](A = PF6, SbF6); the single crystal X-ray structure determination for [(η5-C5Me5)Cr(µ25-P5)Cr(η5-C5Me5)]+[SbF6] reveals that the Cr–Cr separation is 3.185(8)Å which is 0.456 Å longer than in the neutral complex; magnetic susceptibility studies show that these 26-electron multidecker cations in these salts undergo spin crossover at 33 and 23 K respectively.