María S. García-Tasende

Main group metal complexes of semicarbazones and thiosemicarbazones. A structural review

Abstract The structural aspects of the complexes formed by thiosemicarbazones (TSCs) and semicarbazones (SCs) with the metallic elements of Groups 12, 13, 14 and 15 are surveyed up to 1998. Descriptions of 71 structures containing neutral or deprotonated TSCs and ten with SCs include information on the metal-to-ligand bonds and the coordination behaviour of the ligand. The survey shows that TSCs are very versatile coordination agents with these acceptors.

Structural aspects of the coordination chemistry of organothallium(III) and organomercury(II) derivatives

Abstract This review surveys the main structural aspects of the coordination chemistry of mono-, di- and triorganothallium(III) and mono- and diorganomercury(II) complexes. It covers all organothallium(III) derivatives reported up to the end of 1997 and the organomercury compounds reported between 1993 and 1997. Structures are classified primarily by coordination number and secondarily by kernel complexity.

Synthesis, structure, and spectroscopic properties of acetato (dimethyl) (pyridine-2-carbaldehydethiosemicarbazonato)tin(IV) acetic acid solvate, [SnMe2 (PyTSC)(OAc)].HOAc. Comparison of its biological activity with that of some structurally related diorganotin(IV) bis(thiosemicarbazonates)

The synthesis, X-ray structure, behavior in solution, and biological properties of the complex [SnMe2(PyTSC)(OAc)].HOAc (HPyTSC = pyridine-2-carbaldehydethiosemicarbazone) are reported. The tin atom of this complex is coordinated to an N,N,S-tridentate PyTSC- anion, to a monodentate acetate ion, and to the two methyl groups in an approximately pentagonal bipyramidal environment with a vacant equatorial position. The complex partially evolves in DMSO and in DMSO/CHxCl4-x (X = 1, 2) mixtures, giving HPyTSC and SnMe2(OAc)2. [SnMe2 (PyTSC)(OAc)].HOAc, [SnMe2(DAPTSC)], and [SnPh2(DAPTSC)].2DMF (H2DAPTSC = 2,6-diacetylpyridine bis(thiosemicarbazone)) all suppress proliferation of Friend erythroleukaemia cells (FLC). DMSO-induced differentiation of FLC is slightly suppressed by [SnMe2(DAPTSC)] and is unaffected by [SnPh2(DAPTSC)].2DMF and [SnMe2(PyTSC)(OAc)].HOAc.

Synthesis of [2-(pyridin-2′-yl)phenyl]-mercury(II) arylthiosemicarbazonates: An unusual coordination mode of a deprotonated 2-formyl-(2-hydroxy-benzene)-thiosemicarbazone

Abstract The reactions of [2-(pyridin-2′-yl)phenyl]mercury(II) acetate with 2-formyl-benzene-(Hbtsc), 2-formyl-(2-hydroxybenzene)-(H2stsc) and 2-formyl-(4-methoxybenzene)-(Hmbtsc) thiosemicarbazones in ethanol in 1:1 ratio at room temperature formed [Hg(C6H4C5H4N)L] (L=btsc, 1; Hstsc, 2; mbtsc, 3). The derivative [Hg(C6H4C5H4N)L] 2 crystallises in the triclinic space group P\1 (n. 2), Z=2, R=0.0353 and V=906.8(3)A3. Mercury is bonded strongly only to sulphur atom of thiosemicarbazonate anion [Hg–S, 2,357(2)A] and Hg...N(3) distance of 3.126(6)A, slightly less than the sum of the van der Waals radii (3.28 A) shows a weak interaction. The pyridyl nitrogen binds strongly to Hg [Hg–N(4), 2.575(6)A] with a short C(9)HgN(4) bite angle of 74.6(2)°, but Hg retains near linearity in CPhHgS bond angle [177.8(2)°]. 1H and 19;Hg NMR spectra in CDCl3 solution reveal two isomers (A and B) for each of 1–3 and probably also a third isomer (C) for 2. The similarity of 1H and 19;Hg data of B isomers (minor for 1 and 3; major for 2) clearly support that thiosemicarbazones are unidentate S-donors as established for crystallized B isomer of 2 (major) by X-ray study, with pyridyl nitrogen of 2-pyridylphenyl coordinating to Hg. The A isomers (major for 1 and 3; minor for 2) have presumably N3,S-coordinated thiosemicarbazonates with weak Hg–N(pyridyl) interaction and the Hg atom formally tetracoordinated.

Synthesis, crystal structure and spectroscopic properties of bis(diphenyldithiophosphinato)cadmium(II)

Abstract Reacting cadmium(II) perchlorate with the ammonium salt of diphenyldithiophosphinic acid in ethanol yielded the title compound, which crystallized in the triclinic space group P 1 with a = 9.273(1), b = 10.426(1), c = 13.845(3) A, α = 94.38(1), β = 103.16(1), γ = 104.63(1)° and Z = 2. The crystal contains dimeric complexes in which two cadmium atoms and two bridging ligands form an eight-membered ring, the coordination of each metallic centre being made up to four by an additional S,S-dentate chelating diphenyldithiophosphinate ligand. Solid state vibrational spectra (IR and Raman) and multinuclear NMR spectra in DMSO solution (13C, 31P and 113Cd) are discussed and compared with those of aliphatic cadmium(II) dithiophosphinates.

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.

Reaction of dimethylhydroxythallium(III) with 2-thioorotic acid. Crystal structure of dimethyl(2-thioorotato)thallium(III) monohydrate

Abstract Reacting 2-thioorotic acid (H3Tot) and its monosodium salt with dimethylthallium(III) hydroxide yielded the compounds TlMe2H2Tot·H2O and (TlMe2)2HTot·2H2O, respectively. The monometallated compound crystallizes in the P21/n space group with a=9.539(4), b=10.725(3), c=10.892(3) A, β=94.55(3)° and Z=4. The thallium atom is bonded to the methyl carbons and to one of the oxygens of the carboxylate group of a ligand molecule, and forms further weak bonds with a carbonylic oxygen, a carboxylic oxygen and a thiocarbonylic sulfur of other ligands, as well as with the oxygen of a water molecule. The coordination polyhedron about the thallium atom is a deformed pentagonal bipyramid with the methyl groups in the axial positions. In DMSO solution the compound behaves as a 1:1 electrolyte and the ligand signals of its 1H and 13C NMR spectra are analogous to those of NaH2Tot. The coordination characteristics of (TlMe2)2HTot·2H2O are compared with those of the monometallated compound on the basis of spectroscopic properties in the solid state (IR and Raman) and in solution (1H and 13C NMR).

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.

The X-ray crystal structure of bis(dicyclohexyldithiophosphato)cadmium(II)

Abstract The compound bis(dicyclohexyldithiophosphato)cadmium(II), [Cd{S 2 P (OCy) 2 } 2 ], has been obtained by reacting cadmium(II) perchlorate with the sodium salt of dicyclohexyldithiophosphoric acid in ethanol. Its structure was solved by X-ray diffraction. The structure consists of dimers in which each metal centre is coordinated by a chelating ligand and two bridging ligands, giving a coordination number of 4. The two bridging ligands and the two cadmium atoms form an eight-membered ring with a twisted chair conformation.