Annalisa Mancini

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 I3 − 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 I3 − 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.

Reactions Between Chalcogen Donors and Dihalogens/Interalogens: Typology of Products and Their Characterization by FT-Raman Spectroscopy

The chemical bond and structural features for the most important classes of solid products obtained by reacting chalcogen donors with dihalogens and interhalogens are reviewed. Particular attention is paid to the information the FT-Raman spectroscopy can confidently give about each structural motif considered in the absence of X-ray structural analyses.

Square-pyramidal bonding of I2 molecules at the I− nodes of a polyiodide infinite pseudo-cubic 3D-network

The reaction of di-[2]-pyridyl-disulfide (L) with diiodine in molar ratios ranging between 1 : 0.5 and 1 : 5 afforded [(HL+)(I−)·5/2I2] as the only product, containing the first example of a self-assembled infinite polyiodide pseudo-cubic 3D-network featuring distorted square pyramidal I−·5I2 moieties at the nodes.

Synthesis and Characterization of Novel Gold(III) Complexes of Asymmetrically Aryl-Substituted 1,2-Dithiolene Ligands Featuring Potential-Controlled Spectroscopic Properties

The tetrabutylammonium (TBA(+)) salts of square-planar monoanionic gold complexes of the unsymmetrically substituted Ar,H-edt(2-) 1,2-dithiolene ligands (Ar,H-edt(2-)=arylethylene-1,2-dithiolato; Ar=phenyl (1(-)), 2-naphthyl (2(-)), and 1-pyrenyl (3(-))) were synthesized and characterized by spectroscopic and electrochemical methods and the corresponding neutral species (1, 2, and 3, respectively) were obtained in CH(2)Cl(2) solution at room temperature by diiodine oxidation. The single-crystal X-ray diffraction structural data collected for (TBA(+))(2(-)), supported by DFT theoretical calculations, are consistent with the ene-1,2-dithiolate form of the ligand and the Au(III) oxidation state. All complexes feature intense near-IR absorptions (at about 1.5 microm) in their neutral states and Vis-emitting properties in the 400-550 nm range, the energy of which is controlled by the charge of the complex in the case of the 3(-)/3 couple. The spectroscopic and electrochemical features of 1(x-) and 2(x-) (x=0, 1), both in their cis and trans conformations, were investigated by means of DFT and time-dependent (TD) DFT calculations.

Investigation into the reactivity of the coordinatively unsaturated phosphonodithioato [Ni(MeOpdt)2] towards 2,4,6-tris(2-pyridyl)-1,3,5-triazine: goals and achievements

The reaction between the coordinatively unsaturated phosphonodithioato complex [Ni(MeOpdt)2] (1) [MeOpdt = (MeO)(4-MeOC(6)H(4))PS2-] and tptz [2,4,6-tris(2-pyridyl)-1,3,5-triazine] has been investigated. Spectrophotometric and conductometric titrations showed the formation of a neutral and an ionic species, i.e. [Ni(MeOdtp)2(tptz)] (2) and [Ni(tptz)2](MeOdtp)2 (3), in correspondence to 1 : 1 and 2 : 1 tptz : ratios, respectively. XRD studies confirmed the formation of both complexes isolated in the compounds 2.MeOH and 3.4H(2)O. In the neutral complex 2 the central Ni(II) ion features a distorted octahedral coordination, achieved through three N-atoms of tptz and three S-atoms belonging to two MeOpdt anions, one of which unexpectedly acts as a monodentate S-donor. In 3.4H(2)O, the two phosphonodithioato anions are non-coordinating and counterbalance the charge of the [Ni(tptz)2](2+) distorted octahedral complex. From the reaction 2 of with I2 and Br2, crystals of [Ni(tptz)2](I3)2 (5) and [Ni(tptz)Br(micro-Br)]2 (6) have been obtained. The dinuclear complex 6 features a structure showing tubular canals with openings of about 6 x 6 A.