Metal Ion Size and Coordination Mode in Complexes of a β-Diketiminate Ligand with Pendant Quinoline Arms

Marlier, E. E.; Sadowsky, D.; Cramer, C. J.; McNeill, K.
Inorg. Chim. Acta 2011, 369, 173 (doi:10.1016/j.ica.2010.12.021)

A suite of late first row transition metal complexes has been synthesized using a monoanionic nitrogen donor β-diketiminate ligand with quinolyl pendant arms, BDI^QQH (1). [BDI^QQNi]⁺[SO₃CF₃] ^- (2), BDI^QQCuCl (4), BDI^QQZnCl (5) were prepared from the reaction of 1 with Ni(SO₃CF₃)₂, CuCl₂•2H₂O and ZnCl₂, respectively. BDI^QQNiCl (3) was synthesized from an anion exchange of 2 with nBu₄NCl. Reaction of 1 and CoI₂ afforded the unexpected [(BDI^QQ)₂Co] ⁺I^- (6). Through density functional theory (DFT) calculations, ligand geometries in BDI^QQ complexes were investigated and it was found that smaller ionic radius and higher charge destabilize 1:1 metal-ligand complexes relative to alternative 1:2 complexes like 6 owing to significant conformational strain in 1:1 complexes involving metals with small ionic radii. Synthesis and characterization of these complexes, including crystal structures of 4 and 5, are reported, in addition to the results of DFT calculations.