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A series of tetradentate N2O2-type Schiff base complexes with tetravalent 4f- and 5f-block metals, [M(salpn)2] (H2salpn = N,N′-disalicylidene-1,3-diaminopropane; M = Ce, Th, U, Np, and Pu), were prepared to systematically investigate their solid state structure, and their complexation behaviour in solution with the goal to investigate the subtle differences between 4f- and 5f-elements. X-ray diffraction revealed that all investigated metal cations form [M(salpn)2] complexes. All the complexes show the same ligand arrangement with meridional conformation, amongst which only Ce(IV) exhibits unique behaviour upon crystallisation. [Ce(salpn)2] crystallises in two less symmetric systems (P or P21/n), whilst all the other [M(salpn)2] crystallise in a more symmetric orthorhombic system (Pban). Quantum chemical calculations suggest that the observed structural peculiarity of Ce(IV) stems from the geometrical flexibility due to the more “ionic” nature of bonds to the 4f element. 1H NMR measurements revealed that [M(salpn)2] forms two different species in solution with and without an additional solvent molecule, where the relative distribution of the two species depends mainly on the ionic radius of the metal centre. Again, Ce(IV) behaves differently from the tetravalent actinides with a higher ratio of the solvent-molecule-coordinated species than the ratio expected from its ionic radius. Hence, this study is successful in observing subtle differences between 4f- (i.e. Ce) and 5f-elements (actinides; Th, U, Np, and Pu) both in the solid state and in solution on an analytically distinguishable level, and in relating the observed subtle differences to their electronic structure.

Reactions of (NBu4)[TcOCl4] or [TcCl3(PPh3)2(CH3CN)] with in situ-prepared lithium arylselenolates and -tellurolates give (NBu4)[TcVO(ArE)4] (E = Se, Te; Ar = phenyl) and [TcIII(ArE)3(PPh3)(CH3CN)] (E = Se, Te; Ar = phenyl, 2,6-Me2phenyl, mesityl) complexes, respectively. The products contain square-pyramidal (TcV compounds) and trigonal bipyramidal (TcIII complexes) coordinated technetium atoms. Density functional theory calculations indicate that the Tc–chalcogen bonds in the TcIII compounds have a greater bond order than those in the TcV compounds.

The icosahedral cluster-compound WAu12 was recently predicted by Pyykko and Runeberg and experimentally prepared in the gas phase by the group of Lai-Sheng Wang. The photoelectron spectra and electron affinity were reported; the other physical properties remain unknown. Anticipating further experimental studies on it, we report here predicted vibrational spectra, NMR chemical shifts, spin–spin coupling constants and quadrupole coupling constants as well as optical spectra at the level of single and double excitations. The population analysis is non-trivial. By direct numerical integration, a charge of roughly +1 is obtained for the central tungsten atom. The charge distribution is strongly delocalised but bonding regions are clearly seen. A considerable electric field gradient exists at the gold nuclei. Although the radial bonds are strong, the system is quite elastic. The DFT activation energy for rotating one hemisphere against the other one, at a D5h transition state, is only about 20 kJ mol−1. The corresponding hu vibrational frequency is predicted to be slightly below 30 cm−1.

Mercury tetrahydride (D4h) is calculated to have similar bond lengths and vibrational frequencies as the already known HgH2 and to lie energetically 200 kJ mol-1 above HgH2 + H2, in a local well, about 40 kJ mol-1 below a transition state.