Phosphinoquinoline supported CoII, NiII, and FeII complexes: divergent behaviour upon reduction

The reduction of [CoLBr2], a Co-II complex supported by a diisopropylphosphinoquinoline (L) ligand, induced a ligand coupling giving access to a (PNNP) supported Co-II complex which was isolated in 70% yield. This complex was formed using a minimum of 2 equivalents of a reductant (either Mn or KC8). The fate of [CoLBr2] in the presence of 1 equivalent of a reductant was more difficult to study; nevertheless, a Co-I complex was characterised in the solid state. In order to determine whether this ligand coupling could occur with other 3d metals, L supported Fe-II and Ni-II complexes were synthesised. While no compound could be identified upon reduction of [FeLBr2], both [NiLBr2] and [NiL2Br](Br) led to the reduction at the metal center allowing the isolation of an original Ni-0 trimer in a satisfactory yield. This study shows the different behaviours of these 3d metal complexes in the presence of a reductant.

Automated summary

This study investigates the reduction reactions of Co-II, Fe-II, and Ni-II complexes and reveals their different behaviors in the presence of a reductant. The yield of the Co-II complex is 70%, while the Fe-II complex does not yield identifiable compounds. On the other hand, the reduction of the Ni-II complex leads to the isolation of a novel Ni-0 trimer.