Synthesis and X-ray crystal structures of six [TeL4][MF6] salts, where L is ethylene- or trimethylene-thiourea, and M is Si, Ge or Sn. Five Te(II) complexes with a novel type of structure linked together by unusual N–H⋯F hydrogen bonds

Theoretical and Spectroscopic Analysis of Square-Planar Tellurium(II) and Selenium(II) Diphenyl Thiourea Complexes in p2 Electronic Configurations

In this work, we performed a detailed mathematical ligand field theory analysis of square-planar (D4h) main group complexes in p2 electronic configurations, and the results were subsequently used to generate an energy-level correlation diagram. We synthesized the model p2 tellurium(II) diphenyl thiourea coordination complex for further spectroscopic investigation. Dissolution of TeO2 in concentrated HCl resulted in the formation of a [TeCl6]2- complex in acidic media, and subsequent addition of diphenyl thiourea resulted in the reduction of Te4+ to Te2+ (observed by 125Te NMR spectroscopy) and the formation of a cis-Te(dptu)2Cl2 complex, which was characterized by single-crystal X-ray diffraction (XRD). Using in situ optical/magnetic spectroscopy - specifically, UV-vis and magnetic circular dichroism (MCD) spectroscopy - we observed absorbance bands and polarized transitions consistent with the calculated p-orbital splitting in a square planar (D4h) ligand field. Using the results of our spectroscopic investigation, we generated a molecular orbital (M.O.) diagram for the cis-Te(dptu)2Cl2 complex. We then used the M.O. diagram, in conjunction with the energy level correlation diagram, to assign the electronic transitions observed in the spectra of the cis-Te(dptu)2Cl2 complex. The analogous selenium(II) complex, cis-Se(dptu)2Cl2, was used to elucidate the observed transitions with minimal contribution from spin-orbit coupling. Our work examined how in situ spectroscopy and complementary ligand field theory analysis can be used to elucidate the electronic structures of main group coordination complexes.

3,3'-Bis(4-nitro-phen-yl)-1,1'-(p-phenyl-ene)dithio-urea dimethyl sulfoxide disolvate

The asymmetric unit of the title compound, C(22)H(16)N(6)O(6)S(2)·2C(2)H(6)OS, consists of one half-mol-ecule of the centrosymmetric thiourea derivative and one molecule of dimethyl sulfoxide (DMSO). The carbonyl group forms an intra-molecular hydrogen bond with the NH group, creating a six-membered (C-N-C-N-H⋯O) ring. Two other N-H⋯O hydro-gen bonds link one mol-ecule of the thio-urea to two mol-ecules of DMSO.

3,3'-Dibenzoyl-1,1'-(butane-1,4-diyl)-dithio-urea

In the centrosymmetric title compound, C₂₀H₂₂N₄O₂S₂, the carbonyl group forms an intra­molecular hydrogen bond with the NH group attached to the butanediyl linker, resulting in a six-membered ring. There are also inter­molecular C—H⋯S inter­actions in the crystal structure, and π–π inter­actions between phenyl groups [2.425 (3) Å].

The nature of the chemical bond in linear three-body systems: from i3- to mixed chalcogen/halogen and trichalcogen moieties

The 3 centre-4 electrons (3c-4e) and the donor/acceptor or charge-transfer models for the description of the chemical bond in linear three-body systems, such as I(3) (-) and related electron-rich (22 shell electrons) systems, are comparatively discussed on the grounds of structural data from a search of the Cambridge Structural Database (CSD). Both models account for a total bond order of 1 in these systems, and while the former fits better symmetric systems, the latter describes better strongly asymmetric situations. The 3c-4e MO scheme shows that any linear system formed by three aligned closed-shell species (24 shell electrons overall) has reason to exist provided that two electrons are removed from it to afford a 22 shell electrons three-body system: all combinations of three closed-shell halides and/or chalcogenides are considered here. A survey of the literature shows that most of these three-body systems exist. With some exceptions, their structural features vary continuously from the symmetric situation showing two equal bonds to very asymmetric situations in which one bond approaches to the value corresponding to a single bond and the second one to the sum of the van der Waals radii of the involved atoms. This indicates that the potential energy surface of these three-body systems is fairly flat, and that the chemical surrounding of the chalcogen/halogen atoms can play an important role in freezing different structural situations; this is well documented for the I(3) (-) anion. The existence of correlations between the two bond distances and more importantly the linearity observed for all these systems, independently on the degree of their asymmetry, support the state of hypervalency of the central atom.