The striking influence of solubility on the nuclearity of cobalt NCN pincer complexes

Abstract The synthesis and characterization of two Co(II) complexes stabilized by NCN pincer ligands are described. The paramagnetic Co(II) complex [Co(κ 3 NCN- NCN CH2 - i Pr)Br] is obtained via a transmetalation protocol from CoBr 2 and NC(C–Br)N CH2 - i Pr in THF. Surprisingly, the dinuclear complex [Co 2 (κ 3 NCN -μ 2 -NCN CH2 - i Pr)(μ-Cl)(Cl) 2 ] was synthesized following the same synthetic protocol but using an ultrasonicated CoCl 2 suspension instead of CoBr 2 in the same solvent. Both complexes are paramagnetic species exhibiting solution magnetic moments of 1.9(1) and 5.8(3) μ B , respectively. This corresponds to low-spin and high-spin d 7 configurations featuring one and three unpaired electrons at the metal centers. X-ray structures of both complexes are presented. Graphical abstract