Heterodimetallic germanium(IV) complex structures with transition metals

The hydrothermal synthesis and structural characterization of a number of complex compounds containing the divalent tris(oxalato-O,O')germanate anion, [Ge(C2O4)(3)](2-), or the neutral bis(oxalate-O,O')germanium fragment, [Ge(C2O4)(2)], with transition-metal (M) cationic complexes of 1,10'-phenanthroline (phen) is reported: [M(phen)(3)][Ge(C2O4)(3)]center dot xH(2)O [where M2+ = Cu2+ (1a and 1b), Fe2+ (2a and 2b), Ni2+ (3), Co2+ (4); x = 0.2 for 2b], [MGe(phen)(2)(mu(2)-OH)(2)(C2O4)(2)] [where M2+ = Cd2+ (5) and Cu2+ (6)]. The isolation of two polymorphs with Cu2+ (1a and 1b) and other pseudo-polymorphs for Fe2+ (2a and 2b) was rationalized based on slightly different molar ratios for the starting materials. All compounds have been characterized using EDS, SEM, vibrational spectroscopy (FT-IR and FT-Raman), thermogravimetry, and CHN elemental composition and their structure determined on the basis of single-crystal X-ray diffraction studies. The crystal packing of the different chemical moieties for each series of compounds was discussed on the basis of the various intermolecular interactions present (strong C-H center dot center dot center dot pi and weak C-H center dot center dot center dot O hydrogen-bonding interactions, C-H center dot center dot center dot pi and pi-pi contacts).