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Synthesis, Characterization and DFT Studies of (Hdmphen) (H2dmphen)0.5[ReBr4(mal)]. (dmphen). 2H2O

A.Cuevas, M.Pacheco, L.Suescun, H.Pardo, J.Faus, C.Kremer, J.S.Gancheff

Polynuclear ReIVMII (MII = first-row transition-metal ion) complexes are usually obtained froman halide-based rhenium(IV) precursor acting as ligand against a 3d transition metal ion. This synthetic strategy seems not to proceed as expected when [ReBr4(mal)]2– and Fe2+ are considered. Indeed, the reaction of (PPh4)2[ReBr4(mal)] with Fe(ClO4)2·6H2O in the presence of 2,9-dimethyl-1,10-phenanthroline (dmphen) in acetonitrile unexpectedly afforded the complex (Hdmphen)(H2dmphen)0.5[ReIVBr4(mal)]. Themetal ion is observed in a slight distorted octahedral coordination environment in which malonato exhibits a boat conformation. Protonation of two dmphen provides the charge to balance the anionic complex. One of themis resolved as monoprotonated, the other one beingobserved as diprotonated but located on a two-fold symmetry axis of the space group.The crystallographic structure shows several non-covalent interactions, namely, - stacking and different H-bonds connecting water molecules of crystallization. Theoretical Density Functional (DFT) studies on geometry and electronic properties were performed employing B3LYP and PBE1PBE. The general trends observed in the crystallographic data are well reproduced in the calculations. Calculated bond lengths and angles reasonably match the values obtained fromthe X-ray diffraction study. Time-dependentDFT (TDDFT) calculations helped us in assigning the origin of all absorption bandsexperimentally observed.