Pyrazolate-Bridging Dinucleating Ligands Containing Hydrogen-Bond Donors: Synthesis and Structure of Their Cobalt Analogues

Convergent preparative routes to new urea−pyrazolate dinucleating ligands are described. Metal complexes of these ligands have hydrogen bond donors that are proximal to the metal centers that interact with other coordinated species. This is exemplified by CoII dimers with CoII−μ-Cl−CoII motifs, in which the chloro ligand is involved in four intramolecular hydrogen bonds. These noncovalent interactions appear to influence the CoII−Cl bonds, which are unusually long, having lengths greater than 2.5 Å.