Nadia M. Comerlato

Vibrational spectra of bis(dmit) complexes of main group metals: IR, Raman and ab initio calculations

This work reports a theoretical-experimental investigation of the infrared/Raman vibrational spectra of several metal 1,3-dithole-2-thione-4,5-dithiolate (dmit) complexes; [NEt4]2[Zn(dmit)2], [NEt4][Sb(dmit)2] and [NEt4][Bi(dmit)2]. IR/Raman spectra of all the solids and the solution IR spectrum of [NEt4]2[Zn(dmit)2] were recorded from 4000 to 100 cm-1. Two regions were clearly identified: below 380 cm-1, the modes presented significant metal-ligand contributions, and above, the modes indicated major ligand contributions. IR/Raman spectra of NEt4Br have also been recorded. The vibrational bands have been assigned starting from the analysis of related compounds, of previous published spectra and compared to several ECPs (SBK, Stuttgart), basis sets (with and without functions d) and methodologies (RHF, MP2 and DFT). Geometries, frequencies and intensities were calculated and compared to the experimental frequencies seeking secure assignment. Thus, an excellent agreement was obtained for several experimental bands.

Synthesis and properties of bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate(1-) salts, [Q][Bi(dmit)2]. Crystal structure of [AsPh4][Bi(dmit)2]·1/2DMSO: comparison of the solid state structures of [Q][Bi(dmit)2] and [Q][Sb(dmit)2]

Abstract Ionic complexes, [Q][Bi(dmit)2] (5:QNEt4, NBu4, 1,4-Me2-pyridinium and AsPh4), have been obtained from BiBr3 and [Q]2[Zn(dmit)2] [H2–dmit4,5-dimercapto-1,3-dithiole-2-thione]. As established by the crystal structure determination of [(5:QAsPh4)·1/2DMSO], the cations have near tetrahedral geometries and are well separated from the anions. The anions, containing chelating dmit ligands, are linked into chains via Bi–thiolato–S inter-anion bonds: Bi2S2 rings are formed within the chains, with Bi⋯Bi distances alternating between 3.7760(3) and 3.9092(3) A. The bismuth atoms are six-coordinate, arising from two inter-anion Bi–S [Bi–S=3.0391(13) and 3.1643(14) A] and four intra-anion Bi–S bonds [between 2.6680(13) and 2.8370(13) A], with stereochemistries, including the equatorial-sited stereochemically active lone pair, of distorted pentagonal bipyramids. There are no S⋯S contacts between the anions less than the sum of the van der Waals radii. Comparisons are made between the structure of [(5:QAsPh4)·1/2DMSO] and those reported previously for (5:QNEt4), [(5:QNEt4)·1/2Et2O] and [(5:QNBu4) as well as those for [Q][Sb(dmit)2] (4).

Crystal structures of three [bis(1,3-dithiole-2-thione-4,5-dithiolato)zincate]2− salts: [Q]2[Zn(dmit)2] (Q=1,4-Me2-pyridinium or NEt4) and [PPh4]2[Zn(dmit)2]·DMSO. Comparison of the dianion packing arrangements in [Q]2[Zn(dmit)2]

Abstract [Zn(dmit)2]2− dianions in [Q]2[Zn(dmit)2] complexes (2: Q=1,4-Me2-pyridinium (C7H10N) or NEt4), and [PPh4]2[Zn(dmit)2]·DMSO ((2: Q=PPh4)·DMSO) have distorted tetrahedral geometries, as a result of the 94.49(3) to 95.27(3)° range of the bite angle of the dmit ligands; H2-dmit=4,5-dimercapto-1,3-dithiole-2-thione, H2C3S5. The Zn–S bond lengths are in the range from 2.3285(8) to 2.3520(9) A. In (2: Q=C7H10N) and (2: Q=NEt4), both the cations and the dianions are found in alternating layers, which form columns and sheets. Whereas in (2: Q=C7H10N), there are no S⋯S contacts less than the sum of the van der Waals radii, 3.70 A, S⋯S contacts at 3.5792(13) and 3.6605(12) A, within dianion layers, are found in (2: Q=NEt4). In ((2: Q=PPh4)·DMSO), the steric bulk of the [PPh4]+ cations is such that the dianions cannot be distributed in well-defined sheets: no S⋯S contacts less than 4.0 A are found in ((2: Q=PPh4)·DMSO). The structures are compared with those reported for other [Q]2[Zn(dmit)2] compounds.

An experimental and theoretical study of the electronic spectra of tetraethylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)M(III)] and tetraethylammonium [bis(1,3-dithiole-2-one-4,5-dithiolato)M(III)] (M = Sb or Bi)

Metal complexes of dmit and related ligands, such as dmio, have been studied extensively over the last few decades: [dmit](2-) = bis(1,3-dithiole-2-thione-4,5-dithiolato); [dmio](2-) = bis(1,3-dithiole-2-one-4,5-dithiolato). While much effort has been placed on determining structural properties, very few vigorous spectroscopic studies of these metal complexes have been undertaken. The spectroscopic features of the infrared, Raman and UV-vis spectra, previously reported, have largely been used to characterize compounds. In particular, many details of the electronic structure are still to be revealed. We now report a detailed analysis of the UV-vis spectra of the [M(dmit)](-1) and [M(dmio)](-1) anions, where M = Sb(III) or Bi(III). Experimental spectra were deconvoluted and analysed by several theoretical methodologies, including ab initio CI, TD and CISD calculations. The results led to the assignments of several MLCT/LMCT bands, occurring between 390 and 300 nm, and the confirmation of metal orbital contributions to the HOMO-LUMO boundary.

Bis(1,3-dithiole-2-one-4,5-dithiolato)antimonate(1-) salts, [Q][Sb(dmio)2]. Structural comparisons of [Q][Sb(dmio)2] and bis(1,3-dithiole-2-thione-4,5-dithiolato)antimonate(1-) salts, [Q][Sb(dmit)2]

Abstract Bis(1,3-dithiole-2-one-4,5-dithiolato)antimonate(1-) salts, [Q][Sb(C3OS4)2], [Q][Sb(dmio)2] (3: Q=NEt4, 1,4-dimethylpyridinium (DMP), PPh4 or ferrocenyl-CH2NMe3) and bis(1,3-dithiole-2-thione-4,5-dithiolato)antimonate(1-) salts, [Q][Sb(C3S5)2], [Q][Sb(dmit)2] (1: Q=AsPh4 or NBu4) have been obtained from SbBr3–NaSCN and [Q]2[Zn(dmio)2]or [Q]2[Zn(dmit)2]. The crystal structures of (1: Q=AsPh4 or NBu4) and (3: Q=NEt4 and DMP) have been determined. In all cases, the Sb centres are 6-coordinated and, with the inclusion of the lone pair, are considered to have pseudo pentagonal bipyramidal structures. The interanion interactions in these and related complexes are compared.

Crystal structure of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate(1-)], [NBu4][Bi(dmit)2]

Abstract The crystal structure of ionic [NBu4][Bi(dmit)2] (5: Q=NBu4), obtained from BiBr3 and [NBu4]2[Zn(dmit)2], has been determined. The bismuth atoms are six coordinate, as a consequence of two inter-anion Bi–S contacts with two neighbouring anions. In addition to the four intra-anion Bi—S bonds to the two thiolato S atoms of the dmit ligands [Bi–S between 2.5872(14) and 2.8082(13) A: the inter-anion bonds involve thione S atoms [Bi—S(10)i=3.2548(11) and Bi–S(10)ii 3.4628(13) A]. Excluding consideration of any lone pair effect, the Bi atoms have very distorted octahedral geometries. The anions form centrosymmetric pairs of chains with the shortest Bi–Bi distance of 4.180 A being between the pairs of chains; overlapping parallel dmit ligands, within the pairs of chains, are separated by a perpendicular distance of 3.477(2) A, with the dmit centroid–dmit centroid separation of 3.529 A, ideal for π–π interaction.

Bis(2-amidoethyl)tin compounds, (H2NCOCH2CH2—C,O)2SnX2, and complexes: supramolecular arrays derived from hydrogen bonds involving the amido and X units

Abstract Various tin complexes containing the bidentate 2-amidoethyl ligand, H2NCOCH2CH2—C,O, are described. The compounds are [1: (H2NCOCH2CH2—C,O)2SnX2: X = Cl (two polymorphs), X = N3 and the mixed halide, X = Cl/I] and the 1,2-dithiolates, [1: X2 = 1,2-dithiole-3-thione-4,5-dithiolate (dmt) and 1,3-dithiole-2-thione-4,5-dithiolate (dmit)]. Also discussed are the structures of co-crystalline 1 : 1 : 1 complexes, {[NBu4] : [X] : (1)}, namely (2: X = Br and I). The remaining compound considered is the hydrogen bonded 2 : 1 complex of (1: X = Cl) with 18-crown-6, 3. In all of the structures, tin is six-coordinate in an octahedral environment distorted, primarily and most markedly in (1: X2 = dmt or dmit), by the bite angle of the bidentate ligands. The creation of three-, two- and one-dimensional connectivity in the supramolecular structures is dominated by intermolecular hydrogen-bonds with the amide NH2 as the donor species.

Vibrational and electronic spectroscopy of neutral antimony coordination compounds of the 1,3-dithiole-2-thione-4,5-dithiolate (dmit).

The S 1s X-ray absorption near edge structure (XANES) and X-ray photoelectron spectra (XPS) of the neutral complexes [SbL(dmit)] (L = Br or I; dmit =1,3-dithiole-2-thione-4,5-dithiolate) have been measured using tunable synchrotron radiation. The valence shell electronic excitation by ultraviolet-visible (UV-vis) spectroscopy and the infrared vibrational spectra are presented and analyzed. The UV-vis results lead to an assignment of bands at 400 nm as π(Sm) → π*(C═S), where S(m) is the thiolate sulfur. The corresponding S 1s → π*(C═S) transition was identified at 2468.3 eV. Ab initio calculations, within the improved virtual orbital (IVO) method, carried out with the GSCF3 program, were applied to establish a complete and accurate spectral assignment. It has been the first attempt to apply such methodology for dmit coordination compounds, and very consistent results were obtained.

Crystal structures of 4-PhCOS-5-RS-1,2-dithiole-3-thione (R = Me and PhCH2), 4,5-(MeS)2-1,2-dithiole-3-thione and 3,4,5-(MeS)3-1,2-dithiolium iodide

Abstract The crystal structures of the neutral dmt compounds, 4,5-bis(methylthiolato)-1,2-dithiole-3-thione, (1), 4-benzoylthiolato-5-methylthiolato-1,2-dithiole-3-thione, (3) and 4-benzoylthiolato-5-benzylthiolato-1,2-dithiole-3-thione, (4), and the organic salt, 3,4,5-tris(methylthiolato)-1,2-dithiolium iodide (2) have been determined at 120 K. The packing of the molecules provides a variety of intermolecular, or interion, contacts. Notable features in 1 and 3 are the columns of overlapping dithiole rings. In both cases the columns are propagated in the direction of b and neighbouring rings are related to one another by the operation of crystallographic centres of symmetry. In 2 weak C–H · · · I (H · · · I = 3.0236 and 3.0166 Å) and C–H · · · S (H · · · S = 2.8660 Å) hydrogen-bonds, contacts with short I · · · S distances (3.433 and 3.370 Å) and a C–H · · · π contact, with the dithiole ring as acceptor (H · · · Cg = 2.946 Å), create zig-zag chains propagated in the direction of b which are further connected to form corrugated sheets parallel to (0 0 1) with methyl groups on their surfaces. Intermolecular O · · · Sthiole contacts much shorter than the sum of the contact radii (3.32 Å) of oxygen and sulphur are present in 3 and 4.The formation of 3 or 4 occurred regiospecifically from successive reactions of 4,5-bis(benzoylthiolato)-1,2-dithiole-3-thione with one equivalent of caesium hydroxide and RI (R = Me or PhCH2).

Two polymorphs of bis(4-benzoylthio-1,3-dithiole-2-thione)-5,5′-disulphide

Abstract Reaction of caesium 4-benzoyl-1,3-dithiole-2-thione-5-thiolate with iodine produced bis(4-benzoylthio-1,3-dithiole2-thione)-5,5′-disulfide, 6. Compound, 6 has been obtained in two crystalline forms, on recrytsallisation from different organic solvent systems, designated 6X with space group P21/c and 6Y with space group P21. Two enantiomers of the molecule of 6 are observed but both polymorphs are racemates, 6X because of the centrosymmetric space group P21/c and 6Y because of the presence of both enantiomers in the bimolecular asymmetric unit. The polymorphs differ in molecular packing, the resulting intermolecular contacts and the disposition of the enantiomers. In 6X the enantiomers are found in separate stacks of face to face molecules which combine to create channels containing intermolecular C–H · · · O hydrogen-bonds along with π · · · π overlap of rings within and between the stacks. In 6Y the enantiomers are found in separate chains with intermolecular C–H · · · S hydrogen-bonds providing connnectivity within and between the chains and, overall, two-dimensional connectivity in well defined layers of molecules. Stacking of the layers creates stacks of face to face molecules similar to, but less regular than those observed in 6X, in which the enantiomers alternate along the length of the stack.