Abstract

Three structures of novel cluster carboxylates of molybdenum(II) (1a-c) and copper(II) (2) with the OOC-CCHCo 2(CO) 6 ligand are presented. The solvent topology plays an important role in the formation of the crystal lattice of the molybdenum(II) cluster, which shows a pillared structure for 1, with stacked 1,4-xylene (1a,b) and toluene (1c). The nature of the cluster?solvent interaction has been investigated by means of B3LYP density functional theory calculations using double-? basis functions. These DFT calculations together with polarizable continuum media and effective fragment potentials allow us to explain the nature of the arene?Mo 2 arrangement (ca. 3.10 Å) found in the pillared cluster 1b. The copper(II) dimer 2 displays an unexpected weak intramolecular magnetic coupling for a copper tetracarboxylate, which can also be ascribed to the electronic nature of the ligand. The weak coupling within the copper(II) syn,syn-carboxylate cluster was investigated with DFT calculations. In the solvated species the copper(II) cluster 2 presents an oxo ligand at the axial positions, while the molybdenum(II) cluster 1 stacks between the aromatic ligands. © 2006 American Chemical Society.