what is the molecular orbital for copper(II) acetate dihydrate? what's the bond between the two copper metals? is it a triple bond?
- GeorgeSiO2Lv 72 years ago
Copper(II) acetate is a dimer with the two copper atoms bridged by four acetate groups, one H2O ligand bound in the apical site on each Cu.
By convention the O-Cu….Cu-O axis is taken to be a z direction. Cu(II) is d^9 and so each Cu atom has an unpaired electron in the dz^2 AO. A single Cu-Cu would be expected to form, but presumably good overlap cannot be achieved because of the constraints of the bridging acetate ligands. Let’s turn the discussion to C&W: “In these compounds [with other carboxylate ligands] the Cu-Cu varies from ~2.44 – 2.81 Å. There is weak coupling of the unpaired electrons of the unpaired electrons, one on each Cu(II) ion, giving rise to a singlet ground state ([↑↓]) with a triplet state ([↑↑]) lying only a few kilojoules per mole above it; the state is thus appreciably populated at normal temperatures and the compounds are paramagnetic. At 25 °C, μ eff is typically ~1.4 BM/Cu and the temperature dependence is very pronounced.”
So what would you say a Cu…Cu bond order ~0.5 at RT increasing a lower temps?
 F. A. Cotton, G. Wilkinson, C. A. Murillo, M. Bochmann,
Advanced Inorganic Chemistry 6th ed (1999). p 870.