María V. Castaño

TAUTOMERISM IN COORDINATED 1-PHENYL-5-THIONE-1,2,3,4-TETRAZOLE (HL) SYNTHESIS AND CRYSTAL STRUCTURE OF SNME2(PHEN)L2 (PHEN = 1,10-PHENANTHROLINE)

Abstract The compound [SnMe 2 (phen)L 2 ] (phen = 1,10-phenanthroline) was prepared by reaction of a mixture of 1-phenyl-5-thione-1,2,3,4-tetraz phen and SnMe 2 O in 2:1:1 mole ratio in refluxing methanol. The structure of the complex was determined by X-ray diffraction. The unit cell contains two independent molecules. In one, the tin atom is coordinated to the methyl groups, to a bidentate phen and to two N(4)-bound L − , one of which also forms an additional Sn···S secondary bond. In the other independent molecule, the metal atom is coordinated to the methyl groups, to a bidentate phen and to one N - andone S -bound L − which also forms an additional Sn···N secondary bond. Thus the two independent molecules are formally linkage isomers. The IR spectrum was recorded and a multinuclear NMR study was carried out.

Comparative structural study of dimethyl(pyridine-2-thiolato)thallium(III) and dimethylbis(pyridine-2-thiolato)tin(IV)

The crystal structures of the [TlMe2L] and [SnMe2L2](L = pyridine-2-thiolate) have been determined. Dimethyl(pyridine-2-thiolato)thallium(III) crystallizes in the monoclinic space group P21/n(no 14) with a= 8.169(1), b= 13.214(1), c= 8.876(2)A, β= 104.61 (1)°, and Z= 4. Refinement converged to R= 0.047 for 1 531 independent observed reflections. The thallium atom co-ordinates to the two methyl carbons [Tl–C 2.159(8) and 2.199(8)A], to the pyridine nitrogen [Tl–N 2.494(7)A], and to two sulphur atoms [Tl–S 3.160(3) and 2.870(2)A]. Dimethylbis(pyridine-2-thiolato)tin(IV) crystallizes in the monoclinic space group P21/m(no 11) with a= 6.664(5), b= 17.342(5), c= 6.943(3)A, β= 112.53(5)°, and Z= 2. Refinement converged to R= 0.038 for 1 105 independent observed reflections. The tin atom co-ordinates to the two methyl carbons [Sn–C 2.133(9)A], the two pyridine nitrogens [Sn–N 2.702(5)A], and the two sulphur atoms [Sn–S 2.487(2)A]. The structural characteristics of the free ligand are compared with those of the co-ordination compounds, and the mass and 13C n.m.r. spectra of the two complexes are compared.

The crystal structure of dichlorobis(imidazole)dimethyltin(IV)

Abstract The structure of dichlorobis(imidazole)dimethyltin(IV) has been determined by X-ray diffraction. The crystal consists of discrete trans -Me 2 SnCl 2 (HIm) 2 units with the metal atom octahedrally coordinated to two Cl atoms (SnCl, 2.5955(7) A; ClSnCl, 180°), two methyl carbons (SnC, 2.110(3) A; CSnC, 180°), and two imidazole groups (SnN, 2.312(2) A; NSnN, 180°). The imidazole ligands are bound to the metal through their pyridine-like nitrogen atom, and intermolecularly hydrogen-bonded to the chlorine atoms.

COMPOUNDS OF L(+)-ASCORBIC ACID WITH DIMETHYLTHALLIUM(III), DIMETHYLTIN(IV), AND DIBUTYLTIN(IV) : SYNTHESIS, SOLID-STATE SPECTROSCOPY (CP/MAS 13C NMR AND IR), AND MULTI-NMR BEHAVIOR IN AQUEOUS SOLUTION

Reaction of L(+)-ascorbic acid (H2Asc) with TlMe2OOCCH3, SnMe2O, and SnBu2Cl2 (in this last case, in the presence of Et3N) afforded [TlMe2(HAsc)]·12C3H8O, [SnMe2(Asc)], and [SnBu2(Asc)], respectively. The new compounds were studied in the solid state by CP/MAS 13C NMR and IR spectroscopy, and in aqueous solution by 1H, 13C, 205Tl, and 119Sn NMR spectroscopy. The thallium compound behaves as a salt. In the tin derivatives, the metal appears to interact with the (Asc)2− anion through the O(1), O(2), and O(3) atoms of the lactone ring. Other possible weak interactions of the tin complexes in the solid state are also discussed.

Reactions of Cadmium(II) Acetate with Acetoacetanilide and Methylacetoacetate Thiosemicarbazones: A Cyclization Process Leading to a Pyrazolone – The Molecular and Crystal Structures of the Free Ligands and the Complex [CdL2Py] (HL = 2-[Amino(thioxo)methyl]-5-methyl-2,3-dihydro-1H-3-pyrazolone, Py = Pyridine)

Acetoacetanilide- and methylacetoacetate thiosemicarbazones (HTSC1 and HTSC2, respectively) react with cadmium(II) acetate in methanol, giving complexes containing the ligand 2-[amino(thioxo)methyl]-5-methyl-2,3-dihydro-1H-3-pyrazolonate (L–). An X-ray diffraction study of the structures of HTSC1, HTSC2, HL, and [CdL2Py], identified the main structural changes in the cyclization process. Additionally, the coordination of the metal in the complexes [CdL(AcO)] · 2 MeOH and [CdL2] · 3 H2O was analyzed using IR spectroscopy in the solid state and 1H-, 13C-, and 113Cd-NMR spectroscopy in solution. On reaction with aqueous trifluoroacetic acid, both complexes releases the free pyrazolone, which can be easily isolated.

Reactions of thiosemicarbazones derived from β-keto amides and β-keto esters with Zn(II) and Cd(II) acetates: influence of metal, substitution, reagent ratio and temperature on metal-induced cyclization

Zinc(II) and cadmium(II) acetates were reacted in methanol under various experimental conditions with thiosemicarbazones derived from beta-keto amides or beta-keto esters (HTSC). Some of these reactions afforded thiosemicarbazonate complexes [M(TSC)2] with IR and NMR spectra compatible with N,S-coordination, but most gave complexes [ML2], where HL is a substituted 2,5-dihydro-5-oxo-1H-pyrazole-1-carbothioamide resulting from cyclization of the HTSC. Some of these pyrazolonates and two of the HL ligands were studied by X-ray diffractometry, and their structures are discussed. Surprisingly, the reactions of zinc(II) acetate with HTSC in 1:1 mol ratio usually gave a third, previously unreported type of complex with a dideprotonated ligand, [Zn(L-H)], which was also formed when [ZnL2] and Zn(OAc)2 interacted at room temperature in 1:1 mol ratio. These L-H complexes are highly insoluble in all common solvents, which hinders their characterization but suggests that they are polymeric in nature.

Dimethylthallium(III) and methylmercury(II) derivatives of pyridine-2-carbaldehyde thiosemicarbazone: synthesis and structure

The reaction of dimethylthallium(III) hydroxide and methylmercury(II) chloride with pyridine-2-carbaldehyde thiosemicarbazone (HL) and its sodium salt, respectively, afforded [TlMe2(L)] and [HgMe(L)]. The thallium complex crystallizes in the triclinic space group P(no. 2) with a= 11.005(2), b= 12.153(2), c= 10.822(1)A, α= 110.18(1), β= 99.79(1), γ= 70.39(1)°, and Z= 4 (R= 0.031, R′= 0.035). The unit cell has two independent molecules in each asymmetric unit, both containing an N,N′,S-tridentate ligand but with significant differences in bond distances and angles. The 1H NMR spectrum of [TlMe2(L)] in CDCl3 indicates that the bonding scheme observed in the solid state is retained in solution. Infrared data for [HgMe(L)] in the solid state suggest that the metal is N(hydrazinic), S-co-ordinated; in solution in chloroform, [HgMe(L)] consists of a mixture of (E) and (Z) isomers.

Spectroscopic and X-ray studies of bis[dimethylthallium(III)]-1,3,4-thiodiazole-2,5-dithiolato

Abstract The crystal structure of [(TlMe2)2L] (H2L=2,5-dimercapto-1,3,4-thiodiazole, bismuthiol I) has been determined. The compound crystallizes in the orthorhombic space group Fdd2 (No. 43) with a=17.003(2), b=32.810(9), c=9.543(7) A and Z=16 (R=0.049, R′=0.045). The ligand binds to the thallium atoms via an intricate net of weak Tl…N and Tl…S interactions, probably with a strong electrostatic contribution. The 13C CPMAS spectra of H2L and [(TlMe2)2L], and some other spectroscopic properties in the solid state and in solution, are also discussed.

Mercury(II) and thallium(III) organometallic derivatives of 2-Mercaptobenzoxazole

Abstract Some derivatives of 2-mercaptobenzoxazole (HL) of the type MR n L [M = Hg or Tl, R = Me or Ph and n = 1 (Hg) or 2 (Tl)] have been prepared. The structure of HgMeL has been determined by an X-ray diffraction study; in the crystal there are two independent planar molecules in each asymmetric unit, with the ligand in its thiolic form and an almost linear CHgS linkage. Weak intramolecular and intermolecular secondary interactions complement the mercurysulphur bond. The spectroscopic (IR, Raman, mass, 13 C-NMR), conductimetric, and dipolar properties of this and the other compounds are discussed.

Dithiocarbamates of dimethylthallium(III). Crystal structure of dimethyl(di-n-propyldithiocarbamato)thallium(III)

Abstract Six solid compounds of composition [TlMe 2 (dtc)] (where dtc is a dithiocarbamate anion) have been obtained. [TlMe 2 (S 2 CN n Pr 2 )] crystallizes in the space group C 2 with a =19.672(2), b =8.5698(5), c =9.194(2) A, β=116.02(1)° and Z =4. The thallium atom is coordinated to the two sulfur atoms of a slightly anisobidentate dithiocarbamate ligand and to the two methyl groups, which form a highly distorted tetrahedral environment. In the crystal lattice these units are linked by additional weak Tl…S interactions. The main coordination characteristics of this compound seem to be common to the other complexes prepared, both in the solid state and in solution in CDCl 3 or DMSO-d 6 , to judge by their spectral (IR and NMR) properties.