posted on 2023-12-06, 20:35authored byMila Abaeva, Christian Ieritano, W. Scott Hopkins, Derek J. Schipper
With
bimetallic catalysts becoming increasingly important, the
development of electronically and structurally diverse binucleating
ligands is desired. This work describes the synthesis of unsymmetric
ligand 2,7-di(pyridin-2-yl)imidazo[1,2-a]pyrimidine
(dpip) that is achieved in four steps on a multigram
scale in an overall 54% yield. The ability of dpip to
act as a scaffold for the formation of bimetallic complexes is demonstrated
with the one-step syntheses of the dicopper complex [Cu2(dpip)(μ–OH)(CF3COO)3] (4), the dipalladium complex [Pd2(dpip)(μ–OH)(CF3COO)2](CF3COO)·CF3COOH (5), and the dimeric
dinickel complex [Ni4(dpip)2(μ-Cl)4Cl2MeOH6][2Cl] (6) in good
yields (79–92%). All bimetallic complexes were characterized
by spectroscopic methods and X-ray crystallography, which revealed
metal–metal distances between 3.4821(9) and 4.106(2) Å.
Additionally, quantum chemical calculations were conducted on complex 4 and an analogous 1,8-naphthyridine-based dicopper complex
to investigate the differences between the imidazopyrimidine motif
reported here and the widely used 1,8-naphthyridine motif. Natural
bonding orbital (NBO) and Mayer bond order (MBO) analyses validated
the ability of dpip to coordinate metals more strongly.
Finally, NBO calculations quantified the differences in the binding
energy between the two pockets of the unsymmetrical dpip ligand.