Species Trans Research Articles

Reactions of an azine diphosphine with platinum(II) and palladium(II) and the formation of a novel heterocyclic diphosphine ligand. Crystal structure of [Pdl2{PPh2CHC(But)N–NC(But)CH2PPh}

The azine diphosphine Z,ZPPh2CH2C(But)N–NC(But)CH2PPh2I was treated with [Pt-Me2(cod)](cod = cycloocta-1,5-diene) to give the dimethylplatinum(II) complex [[graphic omitted]Ph2}]1a containing a nine-membered chelate ring with an E,Z configuration for the bidentate azine diphosphine ligand. This complex undergoes oxidative addition with Mel to give the fac-trimethylplatinum(IV) complex [[graphic omitted]PPh2}]2. The corresponding platinum(II) complexes [[graphic omitted]PPh2}](X CCC6H4Me-p1b or Cl 1c) were also prepared. Treatment of trans-[PtCl2(NCR)2](R = Me or Ph) with I gave a hexanuclear species trans-[{PtCl2[PPh2CH2C(But)N–NC(But)CH2PPh2]}6]3a in which the azine diphosphine is acting as a bridging group and is still symmetrical, i.e. the configuration is still Z,Z. The palladium analogue 3b was made by treating [PdCl2(NCPh)2] or Na2[PdCl4] with 1 but might only be binuclear. This complex was unstable in hot chloroform and at 60 °C (30 min) was completely converted into the salt [[graphic omitted]PPh2}]Cl 4a in which the azine diphosphine is tridentate with E,Z configuration and mutually trans-co-ordinated phosphorus donors and one of the azine nitrogens is co-ordinated. Treatment of [PtCl2(cod)] with I and addition of NH4PF6 gave the platinum salt [[graphic omitted]PPh2}]PF64c; [[graphic omitted]PPh2}]I 4d was also prepared. On prolonged (8 d) heating in chloroform solution the bridged complex 3b was quantitatively converted into the novel and very stable heterocyclic complex [[graphic omitted]PPh}]5a with loss of a molecule of benzene. Treatment of 5a with LiBr or Nal gave the corresponding dibromide 5b or diiodide 5c complexes. The crystal structure of 5c has been determined. The corresponding platinum complexes [[graphic omitted]PPh}]5d-5f(X = Cl, Br or I) were also prepared and treatment of the dichloro complex with MgMel gave the dimethyl complex 5g. Treatment of this dimethyl complex with an excess of Mel gave [[graphic omitted]PPh}]6. Proton, 13C-{1H} and 31P-{1H} NMR and infrared data are given.

Synthesis and spectroscopic investigation of cis and trans isomers of bis(nitrile)dichloroplatinum(II) complexes

A series of bis(nitrile) complexes cis- and trans-Cl 2Pt(NCR) 2(R=C 6H 5, p-CH 3C 6H 4, p-CF 3C 6H 4, o-CH 3C 6H 4,CH 3, CH 3CH 2, CH 3CH 2CH 2, (CH 3) 2CH, (CH 3) 3C) has been prepared by either one of the two methods, K 2PtCl 4/H 2O/ RCN(excess) or PtCl 2/RCN(neat), both of which usually yield the nitrile complexes as a mixture of cis and trans isomers in different ratios depending on the experimental conditions such as the reaction temperature and the reaction time. The separation of the stereoisomers of each bis(nitrile) compound could be achieved by fractional crystallization by taking advantage of the generally higher solubility of the trans species in non-polar solvents. The complexes were characterized by IR, 1H and 13C NMR spectroscopies. Some general trends of v(CN) and v(PtCl) stretching frequencies as well as of the 2 J(PtC) values have been found to be useful in determining the stereogeometry of the cis and trans isomers of the Cl 2Pt(NCR) 2 complexes.

Synthesis of monomeric, oligomeric and polymeric σ-acetylide complexes of platinum, palladium, nickel and rhodium

Reaction of equimolar quantities of Me 3SnCCRCCSnMe 3 [R = p-C 6H 4; p-C 6H 2(CH 3)2; p-C 6H 4- p-C 6H 4] with the group 10 metal dihalide complexes, [M(X nBU 3) 2Cl 2] (M = Pt, Pd, Ni; X = P, As; Bu = butyl) affords the polymeric species trans-[−M(X nBU 3) 2(-CCRCC-)] n in excellent yields. By varying the stoichiometry of these reactions, complexes of the type trans-[M(X nBU 3) 2(−CCRCCSnMe 3) 2] and trans-[ClM(X nBU 3) 2CCRCCM(X n BU 3) 2Cl], which are precursors to higher oligomers, can be prepared. Treatment of the former with an excess of trans-[M(X nBU 3) 2Cl 2] affords the trimetallic compound trans-[ClM(X nBU 3) 2(−CCRCC−)M(X nBU 3) 2(−CCRCC−)M(X nBU 3) 2Cl], while reaction of the latter with two equivalents of Me 3SnCCRCCSnMe3 followed by two equivalents of trans-[M(X nBu 3) 2Cl 2] gives the complex trans-[ClM(X nBU 3) 2(−CCRCC−)M(X nBu 3) 2(−CCRCC−)M(X nBu 3) 2(−CCRCC−)M(X nBu 3) 2Cl]. Treatment of the complex [Rh(PPhl) 3Cl] (Ph = Phenyl) with one equivalent of Me 3SnCCRCCSnMe 3 [R = p-C 6H 4- p-C 6H 4] gives the polymeric species [−Rh(PPh 3) 2(SnMe 3)(−CCRCC−)] n . Model compounds for other rhodium-containing σ-acetylide complexes have been obtained from the reaction between the complex [Rh(PMe 3) 4Cl] (Me = CH 3) and Me 3SnCCC 6H 5 which yields the compound mer,trans-[Rh(PMe 3) 3-(SnMe 3)(−CCC 6H 5) 2] via the intermediate [Rh(PMe 3) 4(−CH 5]. Reaction of [Rh(PMe 3) 4Cl] with one equivalent of Me 3SnCCRCCSnMe3 [R = p-C 6H 4- p-C 6H 4] yields the polymer mer,trans[−Rh(PMe 3) 3(SnMe 3)(−CCRCC−)] n .

Synthesis of mononuclear and oligomeric ruthenium(II) acetylides

The complexes trans-[Ru(PMe 3) 4(CCPh) 2] and trans-[Ru(PMe 3) 4(CCC 6H 4C 6H 4CCSnMe 3) 2] have been prepared from the reaction between trans-[Ru(PMe 3) 4Cl 2] and an excess of either Me 3SnCCPh or Me 3SnCCRCCSnMe 3 (R = p-C 6H 4C 6H 4), respectively. However, if only one equivalent of the latter reagent is used the rod-like polymeric species trans-[-Ru(PMe 3) 4CCRCC-] n can be isolated.

Electronic effects of bis(acetylacetone) in ruthenium(II) and ruthenium(III) complexes

The compound Ph_4As[Ru(acac)_2CI_2] prepared by the reaction of RuCl_3.•H_2O with acetylacetone in 1 M aqueous KCI. The anion was shown by X-ray crystallography to have a trans configuration, and it is the first trans-bis(acetylacetone) complex to have been prepared. The compound crystallizes in the monoclinic system, in the space group P1, with a = 10.082 (2) A, b = 13.433 (2) A, c = 14.950 (2) A, α = 65.03 (1)°, β = 66.71 (1)°, γ = 72.02 (2)°, V= 1663 (1) A^3, and Z = 2. A number of trans-(acac)_2 complexes of ruthenium(II), -(III), and -(IV) were prepared from the above compound and were characterized by IR, UV-vis, and ^1H NMR spectroscopy and by cyclic voltammetry. They include trans-[Ru(acac)_2(pyrazine)_2] and trans-[Ru(acac)_2(CH_3CN)_2]. The analogous cis complexes were prepared by the reaction of the ligands pyrazine and CH_3CN with Ru(acac)_3 or by thermoisomerization of the trans species, and a comparison of chemical behavior was made. For the acetonitrile derivative, the equilibrium quotient for the isomerization of the trans species to the cis was measured as 80 at 30 °C. Isomerization is so slow for the pyrazine derivative compared to the competing decomposition that a dependable value of the equilibrium quotient could not be determined, but the indications are that the cis form is the more stable. These results, and measurements of the proton affinities of the pyrazine complexes, are rationalized on the basis that when two π-acid ligands compete for π-electron density, this competition is less severe when they are disposed cis, rather than trans, to each other. None of the observations suggest that acac^- acts significantly in a π-acid capacity. When Ru(acac)_2(CH_3OH)_2) and pyrazine, mixed in equimolar proportions, react, a very insoluble polymeric material forms. The solid is a poor conductor, but the conductance is increased by a factor as high as 10^6 when it is doped with I_2.

Linear dichroism and trans → cis photo-isomerization studies of azobenzene molecules in oriented polyethylene matrix

U.v.-vis linear dichroism spectra of trans- and cis-azobenzene in stretched poly(ethylene) (PE) films are reported. Trans → cis photo-isomerization kinetics were measured at 337 nm using polarized light with the electric vector either parallel or perpendicular to the stretching direction of the matrix. Three types of samples were examined, viz. unoriented, kept at constant elongation stretched to (800%) and relaxed (stretched to 600%). Analysis of the kinetic data reveals that the photo-isomerization is purely exponential in time up to 83% conversion, with nearly the same rate constants in both directions. It is faster in the stretched than in the unstretched sample. This suggest that trans å cis isomerization of azobenzene in nonpolar solid solution occurs according to an inversion mechanism. Cis-azobenzene molecules obtained from phototransformation of the trans species in stretched PE attain globular geometry with the phenyl rings twisted perpendicular to the azo plane.

The photochemical methyl migration in (η 5-C 5H 5)Mo(CO) 2LC(O)Me [L = P(OEt) 3, PPh 3, PBu 3

The photolysis of cis- and trans-(η 5-C 5H 5)Mo(CO) 2LMe [L = P(OET) 3, PPh 3, PBu 3] has been studied at 12 K in 1,2-epoxyethylbenzene glass. All the trans species undergo CO loss upon photolysis to generate unsaturated fragments which thermally react with CO to regenerate trans-(η 5-C 5H 5)Mo(CO) 2LMe. The cis species undergo different photochemistry depending on the ligand. For L = P(OEt) 3, CO loss is observed to generate a separate isomer of the unsaturated species, which upon thermal reaction with CO produces cis-(η 5-C 5H 5)Mo(CO) 2P(OEt) 3Me. The photoreaction of cis-(η 5-C 5H 5)Mo(CO) 2LMe, (L = PPh 3, PBu 3) is not CO loss but loss of L from the coordination sphere. FTIR-monitored photolysis of the acetyl derivatives, trans-(η 5-C 5H 5)Mo(CO) 2LC(O)Me [L = P(OEt) 3, PPh 3, PBu 3], leads to the stereospecific production of solely trans-(η 5-C 5H 5)Mo(CO) 2LMe. These products arise from formal CO migration.

Cytotoxicity and antitumor activity of bis(platinum) complexes. A novel class of platinum complexes active in cell lines resistant to both cisplatin and 1,2-diaminocyclohexane complexes

The in vitro cytotoxicity and in vivo antitumor activity of bis(platinum) complexes of general formula [(PtX2-(L))2H2N(CH2)nNH2] (L = NH3, X = Cl or X2 = malonato or where L = py, X = Cl) is reported. Chloride complexes [(PtCl2(NH3]2H2N(CH2)nNH2] may exist as three possible isomers: those containing both coordination units in the cis configuration (2,2/c,c), both coordination units in the trans configuration (2,2/t,t), and the mixed cis,trans species (2,2/c,t), whose synthesis is reported here. The preparation of further complexes with sterically hindered diamine backbones, such as 2,5-dimethyl-2,5-hexanediamine, is exemplified. The biological activity of all complexes were compared. The 2,2/c,c complexes are particularly active in tissue culture in cells resistant both to cisplatin and its 1,2-diaminocyclohexane (dach) analogue. The inhibition of DNA synthesis in L1210/0 cells by the 2,2/c,c complexes is equivalent to that of cisplatin. The presence of at least one cis-[Pt(amine)2] unit appears necessary for activity in cell lines sensitive to cisplatin.

Consistent force field modeling of matrix isolated molecules. V. Minimum energy path potential to the conformer conversion of 1,2-difluoroethane: Ar 364, ab initio calculation of electric multipole moments and electric polarization contribution to the conversion barrier

In this paper results of consistent force field modeling (CFF) of the potential function to conversion of the gauche (g) to the trans (t) conformer of 1,2-difluoroethane (DFE) isolated in an argon matrix will be reported. Starting point are locally stable configurations gDFE:Ar 364 (defect GH1) and tDFE:Ar 364 (TH1) obtained in previous work from CFF modeling of a cube shaped Ar 364 fragment containing one DFE molecule in its center. Using the dihedral angle of DFE as an independent parameter the minimum energy path of the conversion process gDFE:Ar 364→tDFE:Ar 364 will be determined by CFF energy minimization. Determination of the minimum energy path is found to require large numbers of energy minimization steps and to lead to a rather complicated motion of the molecule with respect to the crystal fragment. Surprisingly the molecule-matrix interactions lead to a reduction of the g-t barrier by ≈500 cal/mol and to a stabilization of the trans species by ≈500 cal/mol. This finding is a consequence of a delicate interplay of matrix-molecule and matrix-matrix interactions. Calculation of the electric polarization energy (induced dipole-first-order polarization approximation) is based on extended ab initio calculations of dipole and quadrupole moments and a bond polarizability estimate of the first-order polarizability of DFE as a function of the internal rotation angle, on Fourier expansion of multipole components and use of symmetry for reduction of the order of the linear system defining the (self-consistent) induced dipole moments of all Ar atoms. Electric polarization is found to alter the potential function of the conversion process in a profound way: the g-t barrier and the t-g energy difference are increased to ≈3000 cal/mol and to ≈1500 cal/mol respectively (≈2500 and ≈530 cal/mol respectively for free DFE). Further applications of the technique developed in this work to related problems of matrix isolated molecules, e.g., vibrational matrix shifts will be discussed.

Reaction of tungsten complexes [(.eta.5-C5H4R)Cl2W.tplbond.WCl2(.eta.5-C5H4R)] (R = Me, CHMe2) with alkynes: x-ray crystal structures of [(.eta.5-C5H4Me)2W2Cl4(.mu.-C4Me4)] and [(.eta.5-C5H4Me)2W2Cl2(O)(.mu.-C4Me4)

The dimers [(η 5 -C 5 H 4 R) 2 W 2 Cl 4 ] (1a, R=Pr i ; 1b, R=Me) react with an excess of but-2-yne (C 2 Me 2 ) to give the flyover bridge compounds cis-[(η 5 -C 5 H 4 R) 2 WCl 4 (μ-C 4 Me 4 )] (2a,b), which undergo thermal rearrangement in solution or in the solid state to the isomeric trans species (3a,b). The X-ray crystal structure of 3b reveals a planar bridging μ-C 4 Me 4 group that lies symmetrically perpendicular to the W-W (2.9295 (7) A) bond. Hydrolysis of 2 or 3 gives the monooxoditungsten derivatives trans-[(η 5 -C 5 H 4 R) 2 W 2 Cl 2 (O)(μ-C 4 Me 4 )] (4a,b)

125Te and 19F NMR spectroscopic study of the hydrolysis of pentafluorotellurium chloride: evidence for trans- and cis-HOTeF4Cl and cis, mer-(HO)2TeF3Cl

The hydrolysis of TeF5Cl has been followed by 125Te and 19F NMR spectroscopy. The spectra show that the known series (HO)nTeF6−n(n = 2−6) are present. In addition the spectra are consistent with the presence of the previously unreported series (HO)nTeF5−nCl (n = 1–3) as well as unidentified fluorotellurium(IV) species. Evidence is presented for the new species trans- and cis-HOTeF4Cl and cis, mer-(HO)2TeF3Cl. The course of the hydrolysis of TeF5Cl is compared with that of SF5Cl. Keywords: trans-tetrafluorotellurium hydroxychloride, cis-tetrafluorotellurium hydroxychloride, cis,mer-tetrafluorotellurium dihydroxychloride, pentafluorotellurium chloride, hydrolysis.

Synthesis of hydridotrifluoromethyl complexes of platinum(II). A spectroscopic investigation of the trans and cis influence of ligands in hydridoplatinum(II) compounds

The starting complex trans-[PtH(CF3)(PPh3)2] is prepared from trans-[PtCl(CF3)(PPh3)2] by treatment of the derived labile solvento cathionic species trans-[Pt(CF3)(PPh3)2(solv)]BF4(solv = acetone or CH2Cl2) with NaBH4 in EtOH at 0 °C. The hydridotrifluoromethyl complexes trans-[PtH(CF3)L2][L = PMePh2, PMe2Ph, PMe3, P(CH2Ph)Ph2, P(CH2Ph)2Ph, P(CH2Ph)3, PEtPh2, P(C6H11)3, or P (C6H4Me-4)3] are obtained by reaction of trans-[PtH(CF3)(PPh3)2] with 2 equivalents of phosphine, L, in n-heptane at room temperature. Similar exchange reactions between trans-[PtH(CF3)(PPh3)2] and equivalent amounts of diphosphine, L–L =cis-Ph2PCHCHPPh2, Ph2PCH2CH2PPh2, Me2PCH2CH2PMe2, or Ph2PCH2CH2CH2PPh2, lead to the formation of the corresponding [PtH(CF3)(L–L)] compounds. The hydridotrifluoromethyl complexes with L–L =cis-Ph2PCHCHPPh2 and Ph2PCH2CH2PPh2 can be prepared also by reaction of the parent chloro derivatives [PtCl(CF3)(L–L)] with NaBH4 in EtOH at room temperatue. The mixed isocyanide–phosphine complexes [PtH(CF3)(PPh3)(CNR)][R = 2,6-Me2C6H3, 4-MeOC6H4, or But] are obtained by reaction of trans-[PtH(CF3)(PPh3)2] with a three-fold excess of RNC in n-heptane at room temperature. All the hydridotrifluoromethyl complexes are air-stable in the sold state and in solution. They were characterized by elemental analyses and i.r., 1H, 19F, and 31P n.m.r. spectra. The data obtained for ν(PtH) and 1J(PtH) in trans-[PtH(CF3)(PPh3)2] have been used to compare the trans influence of CF3– with other σ carbon donors,R, in trans-[PtH(R)(PPh3)2] derivatives. The n.m.r.-based trans influence order is CF3– > C6H5– > C6H9– > CH2CH2CN– > CH2CH2CH2CN– > CH3– > CH2CN– > Cl–, wheras the i.r.-based trans influence order is C6H9– > CH2CH2CH2CN– > C6H5–≈ CH3– > CF3– > Cl–. The opposite position of CF3– in the two series of trans influence has been explained by the different mechanism operating on 1J(PtH) and ν(PtH). The first depends predominantly on the s character of the platinum hybrid orbital used in the Pt–H bond, while the second is sensitive also to electrostatic effects induced by the electronegative fluorine atoms. The 1J(PtP) data for the same series of complexes gives the following order of cis influence: Cl– > CH2CN– > CF3–≈ CH3–≈ C6H5–≈ CH2CH2CN– > CH2CH2CH2CN–. From the spectra of trans-[PtH(X)L2](X = CF3 or Cl), the effects of replacing two PPh3 ligands in trans-[PtH(CF3)(PPh3)2] by L on ν(PtH) and 1J(PtH) were measured. With the assumption that the cis effects are additive, the i.r. and n.m.r. parameters were correlated with the electronic χ and steric θ parameters of the phosphine ligands.

The coordination chemistry of bidentate tellurium ligands. I. Complexes of palladium, platinum, and mercury with large chelate rings

Complexes formed from the reaction of palladium(II) and platinum(II) halides with ( p-EtO·C 6H 4)Te(CH 2) n Te(C 6H 4OEt- p) (L n , n = 6, 7, 8, 9, 10) are reported together with data for some mercury(II) complexes, [HgL nCl 2] which are used for comparative purposes. The compounds [ML n X 2] (M  Pd, Pt; n = 7, 8 (Pt only), 9, 10; X  Cl, Br) have molecular weights in molten naphthalene which fluctuate about the monomer value. [ML 6X 2] (M  Pd, Pt; X  Cl, Br) are totally insoluble and are believed to be polymeric. The palladium(II) complexes have trans dichloro groups whereas the platinum compounds show cis dichloro groups in the solid state. 13C NMR spectra are valuable to confirm the coordination of the ligand; the methylene resonance of the TeCH 2 group undergoes a 19–20 ppm downfield shift on coordination. 125Te NMR spectra of the Pd(II) and Pt(II) complexes show two broad resonances the chemical shifts of which imply the presence of cis and trans isomers in CDCl 3 solution. A more detailed variable temperature high field study of [PtL 8Cl 2] ( 125Te and 195Pt NMR) reveals a complex solution chemistry involving at least two cis and two trans species. The temperature range over which the solution is stable (−10 to 70 °C) is insufficient to allow a totally unambiguous interpretation but a model based on monomer ⇍ dimer equilibria provides a self consistent interpretation.

1,2-Bis(dimethyl)phosphinoethane complexes of molybdenum and vanadium. X-ray crystal structure of trans-[MoCl(η 2-NCMe)(dmpe) 2]BPh 4, trans-[Mo(SPh) 2(dmpe) 2], trans-[V(NCMe) 2 (dmpe) 2](BPh 4) 2, trans-[V(CNBu t) 2(dmpe) 2](PF 6) 2

The replacement of chloride in the complexes, trans-[MCl 2(dmpe) 2] M = Mo and V, dmpe = 1,2-bis(dimethyl)phosphinoethane, by various other ligands has been studied. For Mo, acetonitrile gives the species trans-[MoCl(NCMe)(dmpe) 2] +, which has isomers with either η 1- or η 2-MeCN; these react with methanol to give the molybdenum(IV) ethylimido complex [MoCl(NEt)(dmpe) 2] +. Both Mo and V give [M(NCMe) 2(dmpe) 2] 2+ cations. Other complexes synthesized are trans-[MoL 2(dmpe) 2], L = NEt 2, SPh; trans-[VL 2 (dmpe) 2], L = CN, SCN, CS 2; [VL 2(dmpe) 2] +, L = EtCN, tBuNC; [VCl( t BuNC) (dmpe) 2] + and [V(NCMe) 6] 2+. Nuclear magnetic and electron spin resonance spectra of the compounds are reported and the X-ray crystal structure of four of the compounds listed in the title are described.

Ubergangsmetallkomplexe mit Schwefelliganden, XXXIII*/ Transition Metal Complexes with Sulfur Ligands, XXXIII*

Abstract In order to investigate the specific properties which are associated with metal sulfur cen­ters, the system Ru/S2C6H4 2- has been studied with respect to the synthesis of new com­plexes and their reactions as well as their structure. cis-(NBu4)(Ru(NO))(PMe4)(S2C6H4)2] reacts with an excess of PMe3 in boiling THF to give the paramagnetic (μeff = 0,96 B. M., 295 K) trans-(NBu4)(Ru(PMe4)2(S2C6H4)2) (I). A plausible intermediate in this reaction is the nitrido complex (NBu4)(Ru(N)(S2C6H4)2) (2) since 2 gives with one equivalent of PMe3 a very labile product which is probably (NBu4)(Ru(N)(PMe4)(S2C6H4)2) (3). but reacts with an excess of PMe3 even at 20 °C to give 1. The Ru(III) complex 1 is easily oxidized by O2 or PhN2BF4 to yield the diamagnetic Ru(IV) species trans-(Ru(PMe3)2(S2C6H4)2) (4). Remarkably, the transformation of 1 into 4 is achieved also by H+ ions, providing a model reaction for the coupled H+-electron transfer which has been discussed for substrate reactions at metal sulfur centers of enzymes. - The reaction of RuCl2(PMe3)4 with S2C6H4 2- yields [Ru(PMe3)4(S2C6H4)] (5) at 20 °C, even if an excess of S2C6H4 2- is applied. Upon heating in THF or EtOH, 5 looses one PMe3 ligand to give the 16e -complex [Ru(PMe4)4(S2C6H4)] (6) which rapidly coordinates CO to give [Ru(CO)(PMe4)4(S2C6H4)] (7); '1P NMR indicates a meridional coordination of PMe4 in 7, and consequently CO must be trans to S2C6H4 2-. 6 reacts also with LiAlH4 to yield a very sensitive hydride complex to which the tentative formula [Ru(H)2(PMe3)2(S2C6H4)] is assigned. All compounds were characterized by elemental analyses and spectroscopic means, the structures of I and 5 were determined by X-ray structure analysis.

ChemInform Abstract: IR Induced Rotamerization of Halogenoalkanes in Rare Gas Matrices and Vibrational Spectra of the gauche and trans Species.

ChemInform Abstract: IR Induced Rotamerization of Halogenoalkanes in Rare Gas Matrices and Vibrational Spectra of the gauche and trans Species.

DNA repair synthesis in cultured fish and human cells exposed to fish S9-activated aromatic hydrocarbons

1. 1. Unscheduled DNA repair synthesis was measured autoradiographically in cultured rainbow trout gonad (RTG) and human fibroblast (HF) cells following exposure to aflatoxin B 1 (AFB 1), 3,4-benzopyrene (BP), 1,2,5,6-dibenzanthracene (DBA), 1,2-benzanthracene (BA) and pyrene (PY) activated with S9 prepared from rainbow trout liver. 2. 2. S9 from rainbow trout injected with Arochlor 1254 or an oil extract was compared with S9 from Fischer rats injected with Arochlor 1254 for the ability to activate AFB 1 and cause DNA repair in RTG and HF cells. 3. 3. All three types of S9 activated AFB 1, but the measured DNA repair response was greater in the HF cells. 4. 4. A significant grain count response was found following exposure of HF cells to fish S9-activated BP. Using assay conditions which enhance fish cell grain counts, a significant level of DNA repair was also found in RTG cells exposed to fish S9-activated BP. 5. 5. Marginal but statistically significant amounts of DNA repair were elicited in HF and RTG cells exposed to rainbow trout S9-activated BA and DBA, but no response was detected following PY exposure. 6. 6. Fish S9 was found to be able to activate a series of polycyclic aromatic hydrocarbons (PAH) and cause DNA repair synthesis in both fish and mammalian cells. 7. 7. The magnitude of the repair response roughly parallels the carcinogenic potential of the PAHs. 8. 8. These results elicit trans species and phyla comparisons which help to validate fish as models for aquatic carcinogenesis research, and also demonstrate PAH DNA-damaging effects on fish DNA, adcling further credence for studying the effects of these chemicals on aquatic organisms.

Infrared induced rotamerization of halogenoalkanes in rare gas matrices and vibrational spectra of the gauche and trans species

Infrared induced rotamerization of halogenoalkanes in rare gas matrices and vibrational spectra of the gauche and trans species

Mechanisms of reactions of bases with trans-[Mo(NNH2)X(Ph2PCH2CH2PPh2)2]+(X = F, Br, or p-MeC6H4SO3)

The mechanisms of the reactions between trans-[Mo(NNH2)X(dppe)2]+(X = F, Br, or p-MeC6H4SO3; dppe = Ph2PCH2CH2PPh2) and the bases NEt3 and MeO– under an atmosphere of dinitrogen, to give trans-[Mo(N2)2(dppe)2] have been investigated in both methanol and tetrahydrofuran. Initial deprotonation of the hydrazido(2–)-ligand generates trans-[Mo(NNH)X(dppe)2] and the subsequent pathway adopted is determined by the relative labilities of X and the acid strength of the hydrazido(3–)-ligand. Rapid deprotonation of the hydrazido(3–)-complex (X = F or Br) yields trans-[Mo(N2)X(dppe)2]– which loses halide in the rate-limiting step to generate [Mo(N2)(dppe)2]. Subsequent attack by dinitrogen in solution yields the product. However, when X =p-MeC6H4SO3, rapid loss of this ligand occurs from the hydrazido(3–)-complex, to generate, after attack by a molecule of solvent (S) the species trans-[Mo(NNH)S(dppe)2]+. Pathways leading to the product involving either rate-limiting deprotonation or exchange of the co-ordinated solvent for dinitrogen prior to deprotonation have been established, and the factors influencing the choice of pathway are discussed.

Reactions of bis[1,2-bis(dimethylphosphino)ethane]bis(dinitrogen)chromium(0) and -bis(carbonyl)chromium(0) with acids and oxidizing agents. X-Ray crystal structures of trans-CrII(O2CCF3)2(dmpe)2, trans-[CrII(NCR)2(dmpe)2][CF3SO3]2(R = Me or Et), trans-[CrIIICl2(dmpe)2]BPh4·CH2Cl2, trans-[CrI(CO)2(dmpe)2]BPh4, and [Cr0H(CO)2(dmpe)2]BPh4

The interaction of trans-Cr(N2)2(dmpe)2[dmpe = 1,2-bis(dimethylphosphino)ethane] with hydrogen chloride gives the eight-co-ordinate chromium(IV) species CrH2Cl2(dmpe)2 whereas CF3CO2H gives trans-Cr(O2CCF3)2(dmpe)2. Protonation by CF3SO3H of trans-CrL2(dmpe)2(L = N2 or C2H4) in MeCN or EtCN gives the chromium(II) octahedral nitrite species trans-[Cr(NCR)2(dmpe)2]2+(R = Me or Et). The electron spin resonance spectra of the latter are attributed to trace impurities of a chromium(I) nitrite species; the main quintet is typical of CrI with four equivalent phosphorus ligands but hyperfine splitting is ascribed to interaction of CH3 groups of MeCN and CH2 groups of EtCN with the 17-electron chromium(I) atom. The interaction of trans-Cr(N2)2(dmpe)2, trans-CrCl2(dmpe)2, or CrH4(dmpe)2 with CH3I or I2 in methanol leads to compounds of general formula trans-[CrIIIX2(dmpe)2]X′(X = Cl or I, X′= I or BPh4). The interaction of cis-Cr(CO)2(dmpe)2 with CF3SO3H followed by treatment with NaBPh4 in MeOH leads to the seven-co-ordinate [CrH(CO)2(dmpe)2]BPh4, while treatment of the dicarbonyl with one equivalent of AgCF3SO3 leads to trans-[Cr(CO)2(dmpe)2]BPh4. X-Ray structures of the following compounds have been determined: trans-Cr(O2CCF3)2(dmpe)2, trans-[Cr(NCR)2(dmpe)2][CF3SO3]2(R = Me or Et), trans-[CrCl2(dmpe)2]BPh4·CH2Cl2, [CrH(CO)2(dmpe)2]BPh4, and trans-[Cr(CO)2(dmpe)2]BPh4.