Cyclopentadienyl tetranickel clusters

Cyclopentadienyl)tetranickel clusters have not, so far, been intensively studied. The simplest ( / -cyclopentadienyl)tetranickel cluster (NiCp)4, in spite of many efforts, has not been isolated. This unknown species would have the expected closed-shell 60-electron configuration and would be diamagnetic. Such 60-electron species are in fact known, for example (CpCo)4H4. The first (cyclopentadienyl)tetranickel cluster was obtained in the reaction of CpNiNO with LiAlH4/AlCl3 in THF solution at 20 The cluster contains three hydride ligands and has the composition... 

The (cyclopentadienyl)tetranickel cluster (NiCp)4Se2 21 was obtained from the reaction of CpNi(PPh3)Cl with Se(SiMe3)2 (Eq. (19)). 

Several other tetranickel clusters have also been described in the literature but as they do not possess cyclopentadienyl ligands they are not included in this chapter. 

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