Chemical treatment of CoX<sub>2</sub><b><sup>. </sup></b>6H<sub>2</sub>O (X = Cl,
Br, I) with the potentially tridentate PNP pincer ligand 2,6-bis(di-<i>tert</i>-butylphosphinomethyl)pyridine in
1:1 molar ratio results in cobalt(II) halide-PNP pincer complexes. The effect
of the hydrated metal source on molecular structure and geometry of the
complexes was studied by single crystal X-ray diffraction analysis. The
complexes are neutral and the cobalt center adopts a penta-coordinate system
with potential atropisomerization. Within
the unit cell there are two distinct molecules per asymmetric unit. One of the
two phosphorus atoms in the PNP ligand was observed to be partially oxidized to
phosphinoxide. Disorder in the structure reflects a mixture of square pyramidal
and distorted tetrahedral geometry.
Optimised synthesis of monoanionic bis(NHC)-pincer ligand precursors and their Li-complexes