Raymundo Cea-Olivares

S-adenosyl-L-methionine is able to reverse micronucleus formation induced by sodium arsenite and other cytoskeleton disrupting agents in cultured human cells.

Deficiencies of folic acid and methionine, two of the major components of the methyl metabolism, correlate with an increment of chromosome breaks and micronuclei. It has been proposed that these effects may arise from a decrease of S-adenosyl-L-methionine (SAM), the universal methyl donor. Some xenobiotics, such as arsenic, originate a reduction of SAM levels, and this is believed to alter some methylation processes (e.g. DNA methylation). The aim of the present work was to analyze the effects of exogenous SAM on the micronucleus (MN) frequency induced by sodium arsenite in human lymphocytes treated in vitro and to investigate whether these effects are related to DNA methylation. Results showed a reduction in the MN frequency in cultures treated with sodium arsenite and SAM compared to those treated with arsenite alone. To understand the mechanism by which SAM reduced the number of micronucleated cells, its effect on MN induced by other xenobiotics was also analyzed. Results showed that SAM did not have any effect on the increase in MN frequency caused by alkylating (mitomycin C or cisplatin) or demethylating agents (5-azacytidine, hydralazine, ethionine and procainamide), but it reduced the number of micronucleated cells in those treated with agents that inhibit microtubule polymerization (albendazole sulphoxide and colcemid). Since albendazole sulphoxide and colcemid inhibit microtubule polymerization, we decided to evaluate the effect of SAM on microtubule integrity. Data obtained from these evaluations showed that sodium arsenite, albendazole sulphoxide, and colcemid affect the integrity and organization of microtubules and that these effects are significantly reduced when cultures were treated at the same time with SAM. The data taken all together point out that the positive effects of SAM could be due to its ability to protect microtubules through an unknown mechanism.

Tetrahedral versus square-planar NiS4 core in solid-state bis(dithioimidodiphosphinato)nickel(II) chelates. Crystal and molecular structures of Ni[(SPR2) (SPPh2) N]2 (R = Ph, Me)

Abstract Bis(dithioimidodiphosphinato)nickel(II) chelates, Ni[(SPR2) (SPPh2)N]2 (R = Ph (1), Me (2)) were prepared by methathesis reactions between NiCl2·6H2O and the corresponding potassium dithioimidodiphosphinate, in methanol. Compound 1 crystallizes in the triclinic space group P-1, a = 13.336(2), b = 18.580(2), c = 18.670(2) A , α = 90.10(2), β = 93.00(2), γ = 98.21(2)°, Z = 4 , and contains two independent molecules in the unit cell. Compound 2 crystallizes in the monoclinic space group P2 1 /c, a = 13.161(2), b = 10.737(5), c = 12.101(4) A , β = 108.38(2)°, Z = 2 . In both compounds the 1,3-dithiophosphorus ligands act as symmetrical monometallic biconnective (isobidentate chelating) units and the resulting NiS2P2N rings are non-planar. Compound 1 contains a tetrahedral NiS4 core (mean NiS 2.239 A, SNiS 111.9° (endocyclic), 108.2° (exocyclic)), while compound 2 exhibits a square-planar NiS4 core (mean NiS 2.239 A, SNiS 98.3° (endocyclic), 81.1° (exocyclic)). The structures are discussed in relation to previously reported Ni(II) derivatives of 1,1-dithiophosphorus ligands.

Crystal and molecular structure of 1-phenyl-1H-tetrazole-5-thiolato-trimethyltin(IV), Me3SnSCN4Ph, exhibiting unusual trimeric associations through intermolecular N → Sn bonds.

Abstract The title compound is rhombohedral, space group R3, with a = 18.097(4), c = 10.832(5) A, Z = 9, Dc = 1.658 g cm−3. The crystal contains trimeric [Me3SnSCN4Ph]3 units in which the heterocyclic ligand is bridging two metal atoms (Sn(1)-S(1) 2.565(4) A, N(3) → Sn(1a) 2.747(14) A). Additionally, weak intramolecular Sn(1) ⋯ N(4) secondary bonds of 3.285(12) A are also present, thus leading to a bimetallic triconnective coordination pattern of the ligand.

Diorganotin(IV) derivatives of tetraphenylimidodiphosphinic acid. Crystal and molecular structure of n-Bu2Sn[(OPPh2)2N]2, a trans-octahedral spiro-bicyclic compound

Abstract Bis(tetraphenylimidodiphosphinato)diorganotin(IV) derivatives, R 2 Sn[(OPPh 2 ) 2 N] 2 (R = Me, n-Bu, Bz, Ph), were prepared by reacting the appropriate R 2 SnCl 2 with the sodium salt of the phosphorus acid. The compounds were characterized by IR, 1 H, 13 C and 31 P NMR. The crystal and molecular structure of n-Bu 2 Sn[(OPPh 2 ) 2 N] 2 was determined by X-ray diffractometry. The imidodiphosphinato ligands are isobidentate [SnO(1) 2.204(5), SnO(2) 2.202(5), P(1)O(1) 1.520(6) and P(2)O(2) 1.527(6) A]. In the spiro-bicyclic NP 2 O 2 SnO 2 P 2 N system the trans OSnO angles are 180.0(0)°, while the cis OSnO angles are 88.5(2)° (endocyclic) and 91.5(2)° (exocyclic). The SnC 2 moiety is co-linear [CSnC 180.0(0)°] and almost perpendicular to the SnO 4 plane, thus leading to a quasi perfect trans -octahedral geometry around the central metal atom. The structure is compared with that of the previously reported cis -octahedral I 2 Sn[(OPPh 2 ) 2 N] 2 .

A true square-planar tin(II) spiro complex: molecular structure of bis(imidotetraphenyldiselenodiphosphino-Se,Se′)tin(II) and its distorted tetragonal-pyramidal isomer

The yellow complex [Sn{N(SePPh2)2-Se,Se′}2] is the first example of a true square-planar spiro tin(II) compound; the structure of the distorted tetragonal-pyramidal isomer is also described.

New organotin(IV) derivatives of 1-phenyl-1H-tetrazole-5-thiol. Crystal and molecular structure of 1∞[Bz3SnSCN4Ph], a polymer built through secondary intermolecular Sn⋯N bonds

Abstract Di- and triorganotin(IV) derivatives of 1-phenyl-1H-tetrazole-5-thiol, RnSn(SCN4Ph)4−n (R = Me, Bz; n = 2, 3), were prepared by reacting the corresponding organotin chlorides with the ammonium salt of the thiotetrazolato anion. The title compounds were characterized by means of IR and 1H, 13C and 119Sn NMR spectroscopy. The molecular structure of Bz3SnSCN4Ph was investigated using X-ray diffractometry. Data on a redetermination of the crystal and molecular structures of n-Bu2Sn(SCN4Ph)2 are also included, and a comparative discussion of the two structures is presented.

Bis(tetraphenylimidothioxodiphosphinate-S,O)lead(II) · benzene, [Pb{SO(PPh2)2N}2] · C6H6: A new asymmetric chelate compound exhibiting dimeric association through intermolecular Pb…S interactions

Abstract The tetraphenylimidodithioxodiphosphinate (SO(PPh 2 ) 2 N) ion forms a stable bis-chelate with Pb II . The crystal and molecular structure of [Pb{SO(PPh 2 ) 2 N} 2 ] · C 6 H 6 was determined by X-ray diffractometry. Units of [Pb{SO(PPh 2 ) 2 N} 2 ] are associated through intermolecular Pb…S interactions, forming a dimer. This complex displays a very distorted ϕ-trigonal bipyramidal structure at the lead atom with a vacant equatorial position, which may be accounted for by the presence of intermolecular lead-sulphur interactions.

X-ray crystal structure of (tetraphenyldithiomidodiphosphinato) (triphenylphosphine)copper(I), (Ph3P)Cu(SPPh2)2N, a monocyclic inorganic (carbon-free) chelate ring compound

Abstract The mononuclear (Ph3P)Cu(SPPh2)2N compound was prepared by reacting (Ph3P)2CuNO3 with K[(SPPh2)2N] in MeOH/CHCl3 solvent mixture. The 31P NMR spectrum has confirmed the loss of a triphenylphosphine molecule and the formation of the title compound. The crystal and molecular structure was determined by X-ray diffractometry. The compound is monoclinic, space group P2 1 /c, a = 18.826(2), b = 10.619(2), c = 20.587(2) A , β = 112.46(2)°, V = 3803.6(8) A 3 , Z = 4 . The lattice contains monomeric (Ph3P)Cu(SPPh2)2N units, with three-coordinated copper(I) atoms in a distorted trigonal geometry [S(1)CuS(2) 121.5(1), S(1)CuP(3) 126.1(1) and S(2)CuP(3) 112.2(1)°]. The dithioligand is monometallic biconnective and within the resulted CuS2P2N inorganic ring the CuS [2.215(2), 2.258(2) A], SP [2.017(2), 2.012(3) A] and PN [1.582(5), 1.592(5) A] bond lengths suggest a π-electron delocalization over the PNP fragment. The conformation of the six-membered ring is non-planar.

Synthesis, spectroscopic characterization and structural studies of dialkyl dithiophosphinate and N,N-dialkyl dithio- and monothio-carbamate derivatives of 1-iodo-1,1,2,3,4,5-hexahydrotellurophene

Abstract The synthesis of the organotellurium(IV) compounds [C4H8TeI(S2PMe2)] (2), [C4H8TeI(S2PEt2)] (3), [C4H8TeI(S2CNC4H6)] (4) and [C4H8TeI(SOCNC5H10)] (6) was achieved. All of them were characterized by IR, 1H-, 13C-, 31P- and 125Te-NMR, mass spectroscopy, elemental analyses and single-crystal X-ray diffraction. In addition, the crystal and molecular structures of the previously known 1,1-diiodotetrahydrotellurophene and [C4H8TeI(S2CNEt2)] (5) were obtained. The geometry around Te(IV) is that of a sawhorse structure in which the lone pair is apparently stereochemically active and occupying an equatorial position in a distorted trigonal bipyramid. All the structures exhibit different supramolecular associations. The intermolecular Te⋯S and Te⋯I interactions result in the formation of dimeric species in 4, and in 1 and 6, respectively. The intermolecular Te⋯S bonds in 2, 3 and 5 lead to formation of one-dimensional polymers.

CRYSTAL STRUCTURES OF ANTIMONY AND INDIUM PHOSPHINODITHIOATES, M(S2PR2)3 (M=SB, R=ET; M=IN, R=ME, PH). IS THE LONE PAIR RESPONSIBLE FOR THE STRUCTURAL DIFFERENCES?

Abstract The molecular structures of Sb(S 2 PEt 2 ) 3 and In(S 2 PR 2 ) 3 , R  Me and Ph, have been determined by single crystal X-ray diffraction. Both types of compound display distorted octahedral coordination geometry. In the antimony(III) compound the ligand is anisobidentate (unsymmetric) whereas in the indium compounds the coordinated ligands are basically isobidentate (symmetric). The distortions of the geometry are caused by the small bite of the ligands. An attempt is made to rationalize the structural differences observed without invoking lone pair stereochemical activity in the antimony(III) compound.