José S. Casas

The crystal structure and hydrolysis equilibrium of triphenyl(2-mercapto-1-methylimidazolato)tin(IV)

Abstract The title compound was prepared from 1-methyl-2(3H)-inidazolinethione and triphenyltin(IV) hydroxide, and its crystal structure was determined by X-ray diffraction. The crystal consists of discrete molecules with the tin atom coordinated to one carbon atom of each of the three phenyl groups and to the sulfur atom of the deprotonated ligand. An SnN interaction [2.920(3) A] slightly distorts the tin coordination geometry from that of a perfect tetrahedron. NMR spectroscopy was used to study the hydrolysis of this compound in CDC13.

Crystal and molecular structure of spirobicyclic bis(tetraphenyldithioimidodiphosphinato)lead(II), [Pb(SPPh2)2N];2], containing a new inorganic (carbon-free) PbS2P2N chelate ring and Pb(η6-C6H5) interactions

Abstract The title compound, [PbSPPh2)2N];2], was obtained by reacting potassium tetraphenyldithioimidodiphosphinate with lead(II) acetate. X-ray diffraction analysis reveals an unsymmetrical (anisobidentate) coordination of the chelating ligands, indicated by non-equal PbS interatomic distances [2.695(4) and 2.943(4) A] and some PN and PS bond length alternation within the two NP2S2Pb rings that form the spirobicyclic complex. The lead coordination is supplemented by two additional Pb(η6-C6H5) interactions with two phenyl groups. If these interactions are considered, the geometry of the coordination sphere may be described as distorted octahedral.

Cadmium coordination chemistry related to chelate therapy

Abstract Various aspects of the coordination chemistry of cadmium in its dithiocarbamate complexes, which are known to affect the in vivo distribution of this toxic metal ion have been examined. Under appropriate conditions, solid complexes of the composition Cd(DTC)2 have been obtained as reaction products with seven dithiocarbamates. The general properties, octanol/water partition coefficients, mass spectra, 1H, 13C and 113Cd NMR spectra and infrared spectra have been obtained. The molecular structure of the Cd{S2CN(n-C4H9)2}2 complex has been determined. This compound forms monoclinic crystals C2/c a= 23.577(7), b=16.877(8), c=16.209(9) A, β= 126.93(3)o, V=5156(8) A3, Z=8, density=1.343 g cm−3. For the structure determination: λ(Mo Kα)= 0.71073 A, μ=1.076 mm−1, F(000)=2160, T= 296 K and R=0.064 for 1330 observed reflections. The Cd ion is coordinated to four S atoms at distances ranging from 2.513(5) to 2.601(7) A and to a fifth one at the much longer distance of 2.888(5) A. Two of the short metal-sulphur distances are realized by the S atoms of one of the chelate moieties whilst the S atoms of the other moiety realize one short and the longest [2.888(5) A] metal sulphur distance. The other short bond is subtended to a sulphur atom of an asymmetry-related ligand. The coordination polyhedron can be described as either a very distorted tetragonal pyramid or a very distorted trigonal bi-pyramid. The shortest CdCd distance is 3.772(6) A.

Diorganotin(IV)-promoted deamination of amino acids by pyridoxal: SnR2+2 complexes of pyridoxal 5'-phosphate and of the Schiff base pyridoxal-pyridoxamine (PLPM), and antibacterial activities of PLPM and [SnR2(PLPM-2H)] (R = Me, Et, Bu, Ph)

Pyridoxal 5′-phosphate (PLP) and pyridoxal (PL) itself were reacted with diorganotin(IV) derivatives in the presence and absence of aminoacids. With PLP the complexes [SnR 2 (PLP-2H)] (R=Me, Et, Bu) were isolated and characterized by EI and FAB mass spectrometry and by IR, Raman and Mossbauer spectroscopy. Reaction mixtures containing PL, valine or glycine and SnR 2 (OAc) 2 (R=Me, Et) afforded complexes of the form [SnR 2 (PLPM-2H)], where PLPM is the Schiff base formed by condensation of PL and pyridoxamine (PM). PM was presumably formed by transamination between valine or glycine and PL. The PLPM complexes, and their butyl and phenyl analogues, were also synthesized directly by reacting SnR 2 O and PLPM, and were characterized by EI and FAB MS, by IR, Raman, Mossbauer and NMR spectroscopy, and in the case of the methyl and ethyl compounds by single-crystal X-ray diffractometry. Crystals of [SnMe 2 (PLPM-2H)]·H 2 O and [SnEt 2 (PLPM-2H)] consist of molecules in which the ligand is bound to the metal through the O atoms of the two deprotonated phenolic hydroxyl groups and the iminic N atom, and the metal exhibits distorted square pyramidal coordination. Both PLPM and its complexes show intense antibacterial activity against Pseudomonas aeruginosa (ATCC27853), but only the complexes exhibit significant activity against the other four bacterial strains assayed, Staphylococcus aureus , Bacillus subtilis , Escherichia coli and a carbapenem-resistant P. aeruginosa strain.

DIORGANOTIN(IV) COMPLEXES OF PYRIDOXAL THIOSEMICARBAZONE : SYNTHESIS, SPECTROSCOPIC PROPERTIES AND BIOLOGICAL ACTIVITY

The complexes [SnR2(L)] (R = Me, Et, Bu, Ph; H2L = pyridoxal thiosemicarbazone) have been prepared and characterized. In the light of the spectral properties of the complexes in the solid state (IR, mass, Mössbauer) the bideprotonated thiosemicarbazonato anion is O(phenolic)-, N(3)-, S-bonded to the tin atom which probably has trigonal bipyramidal coordination with N(3) atom and R groups occupying equatorial positions. NMR ( 1H, 13C and 119Sn) data in CDCl3 or DMSO-d6 suggest that this coordinative picture remains in these solutions. The ethyl, butyl and phenyl derivatives suppress proliferation of Friend erithroleukaemia cells (FLC). Of the pyridoxal thiosemicarbazone complexes so far evaluated. [SnBu2(L)] and [SnPh2(L)] showed the lowest thresholds for inhibition of FLC proliferation. The effects of these compounds on DMSO-induced differentiation of FLC, DNA synthesis and reverse transcriptase were also assayed.

Reaction of bromopentacarbonylrhenium(I) with ferrocenylcarbaldehyde thiosemicarbazones: the first X-ray diffraction studies of metal carbonyl complexes containing bidentate thiosemicarbazone ligands

Abstract The reactions of [ReBr(CO) 5 ] with ferrocenylcarbaldehyde thiosemicarbazones HL with different groups attached to the amide nitrogen (R=H, Me, Ph) yielded complexes [ReBr(CO) 3 (HL)] ( 1 ) in which, according to X-ray studies of 1a ·{(CH 3 ) 2 CO} and 1b ·1/2{CH 2 Cl 2 }, the thiosemicarbazone is N , S -bidentate and the geometry around the metal fac -octahedral. Compounds of formula [ReL(CO) 3 ] 2 ( 2 ) were then prepared by reaction of the corresponding adduct 1 with NaOMe in acetone. A complex of formula [ReL 2 (CO) 3 ] 2 ( 2b ′) was also obtained as a dissolvate by slow concentration of a solution of 1b in acetone. Single crystals of 2a and 2b obtained from the mother liquors are composed of centrosymmetric dimers formed by ReSRe bridges, where S is the thiolic sulfur of an N , S -bidentate thiosemicarbazonato ligand. Although 2b ·2{(CH 3 ) 2 CO} and 2b ′·2{(CH 3 ) 2 CO} have similar co-ordination spheres, they differ as regards the configuration of the thiosemicarbazonato ligand about the azomethine bond and certain bond lengths (notably ReN); it seems likely that the configuration of L 2− determines how close the rhenium can approach the N atom of the ligand, and hence the delocalization of the π electrons in the CNN fragment of the thiosemicarbazide chain. The mass, IR and UV–vis spectra of the complexes, and their electrochemical behavior, are also discussed.

Pd(II) and Pt(II) complexes of 2,2'-biimidazole and its N, N'-dimethyl derivative. The crystal structure of [{PtBr(DMSO)}2(Me2bim)] (Me2bim = N, N'-dimethyl-2,2'-biimidazole)

Abstract The complexes [PdCl2(LL)] and [PtX2(LL)] [X=Cl, Br or I; LL=2,2′-biimidazole (H2bim) or N,N′-dimethyl-2,2′-biimidazole (Me2bim)] were prepared and characterized spectroscopically. The effects of the chloro compounds on plasmid DNA conformation were studied by electrophoresis in agarose gels, and that of [PtCl2(H2bim)] on calf thymus DNA by circular dichroism spectroscopy. The observation that these effects were adversely affected by addition of DMSO (originally used with [PtCl2(Me2bim)], to improve its solubility) prompted a study of the solvolysis of [PtCl2(H2bim)] by this solvent. 1H and 195Pt NMR, and electrospray mass spectra, showed the solvolysis of both PtCl and PtN bonds, the release of the ligand H2bim, and the formation of several polynuclear species. X-ray diffractometry of the dinuclear Pt(I) compound [{PtBr(DMSO)}2(Me2bim)] showed the ligand Me2bim to bridge through its non-methylated N atoms between two platinum atoms, the coordination spheres of which were each completed by a Br− ligand, the S atom of a DMSO molecule, and the other Pt atom; the PtPt bond is 2.5560(9) A in length.

Reaction of the diethyltin(IV) cation with pyridoxine (PN, vitamin B6) in the presence of various anionic species: the crystal structure of [SnEt2(PN–H)]Cl

Abstract Reaction of the diethyltin(IV) cation with pyridoxine (PN, vitamin B6) in 80:20 (v/v) ethanol–water mixtures containing NO3− and Cl−, NO3− and AcO− or Cl− and AcO− ions in various molar ratios was investigated. The compounds [SnEt2(PN–H)]Cl (1), [SnEt2(PN–H)](NO3)·2H2O (2) and [SnEt2(PN–2H)] (3) were isolated. These compounds were characterized by IR, Raman and Mossbauer spectroscopy and EI and FAB mass spectrometry. The structure of compound 1, determined by X-ray diffraction, consists of dimeric [SnEt2(PN–H)]22+ units (in which two bridging-chelating hydrogen pyridoxinate anions link Sn atoms with coordination number five) and hydrogen-bonded Cl− ions. The behaviour of these compounds in DMSO-d6 and DMF-d7 was studied by NMR spectroscopy.

Synthesis, structure, spectroscopic properties and biological activity of mixed diorganotin(IV) complexes containing pyridine-2-carbaldehyde thiosemicarbazonato and diphenyldithiophosphinato ligands.

Reaction of the title ligands (HPyTSC and HS(S)PPh2, respectively) with R2SnO (R = Me, Et, Bu) in ethanol (EtOH) afforded the complexes [SnMe2(PyTSC) (S2PPh2)].EtOH (1) and [SnR2(PyTSC) (S2PPh2)] (R = Et (2), Bu (3)). The structures of 1 and 2 were determined by single-crystal X-ray diffractometry. In both these complexes the tin atom is coordinated to an N,N,S-dentate thiosemicarbazonate ligand, an anisobidentate dithiophosphinato ligand and the two R groups. The coordination polyhedrons can be described as distorted pentagonal bipyramids. A comparative study of the IR spectra of 1, 2 and 3 indicates that the butyl complex has a similar structure. Multinuclear (1H, 13C, 31P and 119Sn) NMR data suggest that the structures of 1 and 2 probably remain in CDCl3 (or DMSO-d6) solution but compound 3 partially decomposes in these media. Preliminary results on the effects of the complexes on the proliferation and differentiation of FLC, CEM, U937, K562 and TOM-1 leukaemia cells, and on the clonogenic activity of K562 cells are also described.

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.