Abstract
The copper coordination chemistry of two multidentate carboxamido ligands derived from HL(1) (offering two quinolyl and one carboxamide donor) and H(4)L(2) (with two pyridine(dicarboxamido) units linked by naphthalene spacers) was explored. The former was chosen because upon deprotonation it would provide a monoanionic mer-coordinating N-donor set that would model the putative deprotonated form of the His-brace in copper monooxygenases, while the latter was designed to bind two copper ions and enable comparisons to other systems with different ligand spacers. Upon reaction with Cu(I)-mesityl, HL(1) yielded a symmetric dimer (L(1)Cu)(2) in which each bis(quinolyl)amide ligand binds via two N-donors to one Cu(I) ion and via the third to the other Cu(I) center. Monomeric Cu(II) complexes [L (1) Cu(H (2) O) (2) ](OTf) and L (1) (2) Cu were also characterized. Treatment of H(4)L(2) with Cu(OTf)(2) and excess Me(4)NOH (in CH(3)CN, pyridine/H(2)O, or MeOH) yielded complexes with anions of general formula [L (2) Cu (2) (X)](n-), where X = CH(3)CONH(-) (n = 1), CO(3) (2-) (n = 2), or MeO(-) (n = 1). X-ray structures of these complexes revealed the (L(2))(4-) ligand binding to two Cu(II) ions in an open paddle-wheel geometry, with an additional bridging ligand (X) completing the square planar coordination sphere of each metal ion. The open paddlewheel motif differs from the more 'open' puckered geometry seen with related ligands with different spacer units.