Synthesis of some mixed seven-coordinate complexes of the type [MI2(CO)3LL′] (M = Mo or W;L = pyridine or substituted pyridines; L′ = PPh3, AsPh3 or SbPh3)

The seven-coordinate bisacetonitrile complexes [MI₂(CO)₃(NCMe)₂] (M = Mo or W) react with L′ (L′ = PPh₃, AsPh₃ or SbPh₃) in CH₂Cl₂ at room temperature to give [MI₂(CO)₃(NCMe)L′] which when reacted in situ with L (L = pyridine or substituted pyridines) affords good yields of 28 mixed seven-coordinate complexes [MI₂(CO)₃LL′]. It is likely these reactions occur via successive dissociative displacements of two acetonitrile ligands.     

Natural CO(2) springs: obstacle or opportunity?

Plant Responses to Elevated Carbon Dioxide: Evidence from Natural Springs edited by A. Raschi, F. Miglietta, R. Tognetti and P.R. van Gardingen Cambridge University Press, 1997. ￡40.00/$69.95 hbk (xiv+272 pages) ISBN 0 521 58203 2.     

Does succinate oxidation yield FADH(2) or ubiquinol?

Most textbooks still show the oxidation of succinate in the tricarboxylic acid (TCA) cycle resulting in the reduction of FADH(2). Such a presentation does not reflect the reaction catalysed by the enzyme in vivo or in vitro, does not simplify the treatment of the reaction, and is unnecessarily misleading and confusing.     

Nickel(II) α-diimine catalysts for the atom transfer radical polymerization of styrene

The synthesis and evaluation of ^Cy[N,N]NiX₂ complexes (where ^Cy[N,N] = C₆H₁₁NCHCHNC₆H₁₁; X = Cl, Br) as catalysts for atom transfer radical polymerization are reported. ^Cy[N,N]NiCl₂ offers poor control over the polymerization of MMA and styrene due to catalyst insolubility. The more soluble bromo catalyst ^Cy[N,N]NiBr₂, promotes rapid styrene polymerization, but with inefficient initiation, affording higher than expected molecular weights based on [M]_o/[I]_o ratios. Utilizing 1-PEBr results in efficient initiation to give low polydispersities (M_w/M_n ∼ 1.2) and polystyrene molecular weights that correlate with monomer:initiator ratios.     

Computational investigation of the geometric structures of [(CN)5PtTl(CN)n]n− (n=0, 1, 2 or 3)

[(CN)₅PtTl(CN)_n]ⁿ⁻ (n=0–3, complexes I–IV) have been studied computationally using quasi-relativistic gradient-corrected density functional theory. Good agreement is obtained with previous EXAFS and Raman data for complexes II–IV, but calculations significantly overestimate the PtTl bond length and underestimate ν(PtTl) for complex I. The addition of co-ordinating water molecules to the thallium atom in complexes I–III has little effect on complexes II and III, but significantly shortens the PtTl bond in complex I, bringing it into excellent agreement with experiment. The bond length shortening is traced to intramolecular hydrogen bonding. The total molecular bonding energies of hydrated I and I′ (in which the axial ligands on the thallium and platinum atoms are interchanged) are found to be very similar to one another, suggesting that complex I might exist as a mixture of isomers in solution.     

Expression of Fertility during Morphogenesis in Self-Pollinated Backcrossed Progenies of Barley—Wheat Amphiploids [Hordeum geniculatum All. (2n = 28) × Triticum aestivum L. (2n = 42)] (2n = 70)

The fertility characteristics expressed during morphogenesis in first-generation self-pollinated backcrossed progenies (BC₁) obtained from amphiploid barley–wheat hybrids [Hordeum geniculatum All. (2n= 28) ×Triticum aestivum L. (2n= 42)] (2n = 70) backcrossed with common wheat were studied. It was found that, in the case of self-pollination of BC₁ plants, karyotype stabilization leads to the formation of alloplasmic euploid (2n = 42), telocentric substitution (2n = 40 + 2t), and telocentric addition (2n = 42 + t), (2n = 42 + 2t) plant forms, which may serve as the sources of the respective alloplasmic lines of common wheat. That the expression of fertility characters in BC₁F₈plants was shown to depend on growth conditions. The main mechanism of hybrid incompatibility of BC₁F₁–BC₁F₈plants was expressed as grass-clump dwarfism.     

New synthesis of seven-coordinate complexes of molybdenum(II) and tungsten(II) containing bidentate phosphorus ligands, [MI2(CO)3{Ph2P(CH2)nPPh2}] (n = 1–6)

A new high yielding synthesis of the seven-coordinate complexes [MI₂(CO)₃{Ph₂P(CH₂)_nPPh₂}] (M = Mo and W; n = 1–6) is described. The procedure involves reacting the complexes [MI₂(CO)₃(NCMe)₂] in CH₂Cl₂ with an equimolar amount of the bidentate phosphorus ligand. The low temperature (−70 °C) ¹³C NMR spectra of the complexes [Wl₂(CO)₃{Ph₂P(CH₂)_nPPh₂}] (n = 3 and 5) indicates that the geometry is capped octahedral with a carbonyl ligand in the unique capping position.     

Theoretical studies on all-metal binuclear sandwich-like complexes M2(η4-E4)2 (M=Al, Ga, In; E=Sb, Bi)

A series of all-metal binuclear sandwich-like complexes with the formula M(2)(η(4)-E(4))(2) (M=Al, Ga, In; E=Sb, Bi) was studied by density functional theory (DFT). The most stable conformer for each of the M(2)(η(4)-E(4))(2) species is the staggered one with D (4d) symmetry. The centred metal-metal bond in each M(2)(η(4)-E(4))(2) species is a covalent single bond, with the main contributors to these covalent bonds being the a(1) and e orbitals. For all these species, the interactions between the centred metal atoms and the all-metal ligands are covalent; η(4)-Sb (4) (2-) has a stronger ability to stabilize metal-metal bonds than η(4)-Bi (4) (2-). Nucleus-independent chemical shifts (NICS) values and molecular orbital (MO) analysis reveal that the all-metal η(4)-Sb (4) (2-) and η(4)-Bi (4) (2-) ligands in M(2)(η(4)-E(4))(2) possess conflicting aromaticity (σ antiaromaticity and π aromaticity), which differs from the all-metal multiple aromatic unit Al (4) (2-). In addition, all of these M(2)(η(4)-E(4))(2) species are stable according to the dissociation energies of M(2)(η(4)-E(4))(2)?→?2 M(η(4)-E(4)) and M(2)(η(4)-E(4))(2)?→?2 M?+?2E(4), and these stable species can be synthesized by two-step substitution reactions: CpZnZnCp?+?2E (4) (2-) →?[E(4)ZnZnE(4)](2-)?+?2Cp(-) and [E(4)ZnZnE(4)](2-)?+?2 M (2) (+) →?E(4)MME(4)?+?2Zn(+).     

Synthesis of (NBu4)2[Pd2(μ-Br)2(C6X5)2Br2] (X=F,Cl), new and more versatile precursors of pentahalophenyl derivatives of palladium(II)

The title compounds (1, X=F; 2, X=Cl) were obtained in quantitative yield by refluxing together (NBu₄)₂[Pd₂(μ-Br)₂(C₆X₅)₄] and (NBu₄)₂[Pd₂(μ-Br)₂Br₄]. Treatment of 1 or 2 with AgClO₄ (Pd:Ag= 1:1) gave solutions which behaved as containing ‘Pd(C₆X₅)Br’. 1, 2 and the ‘Pd(C₆X₅)Br’ solutions were checked as precursors of mono-pentahalophenyl derivatives, yielding a variety of complexes [Pd(C₆X₅)Br(L-L)] (L-L=bipy, tmen, dpe, COD), [Pd(C₆X₅)BrL₂] (L=p-TolNH₂, py, PPh₃, AsPh₃, SbPh₃), [Pd₂(μ-Br)₂(C₆X₅)₂L₂] (X=F, L=AsPh₃; X=Cl, L=SbPh₃) and (NBu₄)[Pd(C₆X₅)Br₂L] (X=F, L= py, AsPh₃, SbPh₃; X=Cl, L=p-TolNH₂, py, PPh₃, AsPh₃, SbPh₃). The solutions of ‘Pd(C₆X₅)Br’ proved to be the best general precursors of complexes [Pd(C₆X₅)BrL₂] although complexes with OPPh₃ could not be obtained.     

Barley Chromosome Identification Using Genomic in Situ Hybridization in the Genome of Backcrossed Progeny of Barley–Wheat Amphiploids [Hordeum geniculatum all. (2n = 28) × Triticum aestivum L. (2n = 42)] (2n = 70)

Genomic in situ hybridization (GISH) has been used to study characteristics of the formation of alloplasmic lines detected among self-pollinated backcrossed progeny (BC₁F₅–BC₁F₈) of barley–wheat amphiploids [Hordeum geniculatum All. (2n = 28) × Triticum aestivum L. (2n = 42)] (2n = 70). The chromosome material of the wild barley H. geniculatum has been shown to contribute to these lines. For example, fifth-generation plants (BC₁F₅) had genotypes (2n= 42w + 2g), (2n = 42w + 1g + 1tg), and (2n = 41w + 1g), where w is common wheat chromosomes, g is barley (H. geniculatum) chromosomes, and tg is the telocentric chromosome of wild barley. Beginning from theBC₁F₆ generation, alloplasmic telocentric addition lines (2n= 42 + 2tg) and (2n = 42 + 1tg) appear. This lines has been found cytogenetically unstable. The progeny of each of these cytological types include not only the (2n= 42 + 2tg) and (2n = 42 + 1tg) addition plants, but also plants with the monosomic (2n = 41 + 1tg) and the disomic (2n = 40 + 2tg) substitutions, as well as the (2n = 41 + 2tg) plants, which lack one wheat chromosome and have two telocentric barley chromosomes. It has been demonstrated that the selection for well-filled grains favors the segregation of telocentric addition lines (2n = 42 + 2tg) and (2n = 42 + 1tg).     

Stoichiometry and products of transmetalation of dimeric copper(I) complexes L2Cu2X2 (L is an N,N,N′,N′-tetraalkylethylenediamine; X = Cl or Br) by M(NS)2 reagents in aprotic solvents

Dimeric copper(I) complexes L₂Cu₂X₂ react with 1 and 2 mol of M(NS)₂ reagents in aprotic solvents to give quantitative yields of products LMX₂ and (NS)M(X,X)M(NS), respectively. Here, L = N,N,N′N′-tetraethylethylenediamine, X = Cl or Br, M = Co, Ni, Cu and Ns = S-methylisopropylidenehydrazinecarbodithioate. Dimers (NS)Cu(X,X)Cu(NS) are oxidatively unstable. LCoCl₂ crystallizes in the monoclinic space group P2₁/c (C_2h⁵): a = 7.345(1), b = 11.801(1), c = 17.478(2) Å, β = 104.98(1)°, Z = 4. The electronic spectra of LMX₂ and (NS)M(X,X)M(NS) complexes are discussed.     

The reactivity of bromoform with [Au(CH2)2PPh2]2. The completion of the halomethane series CHyX4−y (y=3,2,1,0; X=Cl,Br, I) and reactivity with [Au(CH2)2PPh2]2

The reaction of [Au(CH₂)₂PPh₂]₂ with excess CHBr₃ in benzene initially gives [Au(CH₂)₂PPh₂]₂₋ (CHBr₂)Br. This observation establishes that halomethanes, CH_yX_4−y (y=3,2,1,0; X=Cl, Br, I), react with [Au(CH₂)₂PPh₂]₂ to initially give Au(II) adducts of the general form [Au(CH₂)₂PPh₂]₂₋(CH_yX_3−y)X (y=3,2,1,0) via oxidative addition across the carbon-halogen bond. The order of reactivity inversely follows the order of carbon-halogen bond dissociation energies of haloalkanes. Methyl chloride is the only halomethane of the series that does not give a Au(II) adduct under similar reaction conditions.     

Preparation and physico-chemical studies of some chloride and alkoxide isopropoxymetallates of cobalt(II) containing {Al(OPri)4}−, {Zr2(OPri)9}− and {M(OPri)6}− Units (M = Nb or Ta)

Chloride isopropoxymetallates of cobalt(II), [ClCo{Al(OPrⁱ)₄}], [ClCo{Zr₂(OPrⁱ)₉}] and [ClCo{M(OPrⁱ)₆}] (M = Nb or Ta) have been synthesized by reactions of CoCl₂ with Li{Al(OPrⁱ)₄}, K{Zr₂(OPrⁱ)₉} and K{M(OPrⁱ)₆} in equimolar ratio. The chlorine in these chloride bimetallic isopropoxides has been replaced with alkoxide groups by their reactions with potassium alkoxides yielding products of the types, [(OR)Co{Ta(OPrⁱ)₆}] and [(OR)Co{Zr₂(OPrⁱ)₉}] (R=Me, Prⁿ, Prⁱ, Buⁿ, Bu^s or Bu^t). Alcohol interchange reactions of the above derivatives have been studied. All these new bimetallic alkoxides of cobalt(II) have been characterized by elemental analyses, IR, electronic spectral (visible) and magnetic susceptibility measurements.     

Nitrous oxide reduction in nodules: denitrification or n(2) fixation?

Detached cowpea nodules that contained a nitrous oxide reductase-positive (Nor) rhizobium strain (8A55) and a nitrous oxide reductase-negative (Nor) rhizobium strain (32H1) were incubated with 1% N(2)O (95 atom% N) in the following three atmospheres: (i) aerobic with C(2)H(2) (10%), (ii) aerobic without C(2)H(2), and (iii) anaerobic (argon atmosphere) without C(2)H(2). The greatest production of N(2) occurred anaerobically with 8A55, yet very little was formed with 32H1. Although acetylene reduction activity was slightly higher with 32H1, about 10 times more N(2) was produced aerobically by 8A55 than by 32H1 in the absence of acetylene. The major reductive pathway of N(2)O reduction by denitrifying rhizobium strain 8A55 is by nitrous oxide reductase rather than nitrogenase.     

鹅观草属——人工合成双二倍体(2n=10x=70)的细胞学及育性的研究

本文对缘毛鹅观草（Roegneria pendulina）、鹅观草（R.tsukushiensis var.transiens）及其人工合成杂种F1、双二倍体进行了细胞学,育性等的分析和研究。结果表明双亲的减数分裂,花粉育性和结实性均正常,杂种F1的减数分裂不规则且完全不育;当代双二倍体的染色体数目为70,其减数分裂构型为:6.04 Ⅰ+26.21 Ⅱ+1.52 Ⅲ+1.59 Ⅳ+0.02 Ⅴ:第二代双二倍体的染色体数目为70,个别植株为69,减数分裂构型分别为:4.16 Ⅰ+27.33 Ⅱ+0.50 Ⅲ+2.16 Ⅳ和4.79 Ⅰ26.26 Ⅱ+1.13 Ⅲ+2.13 Ⅳ。与期望染色体配对模式相比,双二倍体中二价体出现的频率有明显增大的趋势。在减数分裂AⅠ和AⅡ分别观察到数目不定的落后单价体,大部份的四分体中出现了微核。双二倍体的育性得到了很大程度的恢复,其花粉可染色性及结实率分别为54.4％和64.0％。     

鹅观草属——人工合成双二倍体(2n=10x=70)的细胞学及育性的研究

本文对缘毛鹅观草(Roegneria pendulina)、鹅观草(R.tsukushiensis var.transiens)及其人工合成杂种F_1、双二倍体进行了细胞学,育性等的分析和研究。结果表明双亲的减数分裂,花粉育性和结实性均正常,杂种F_1的减数分裂不规则且完全不育;当代双二倍体的染色体数目为70,其减数分裂构型为:6.04 Ⅰ+26.21 Ⅱ+1.52 Ⅲ+1.59 Ⅳ+0.02 Ⅴ:第二代双二倍体的染色体数目为70,个别植株为69,减数分裂构型分别为:4.16 Ⅰ+27.33 Ⅱ+0.50 Ⅲ+2.16 Ⅳ和4.79 Ⅰ26.26 Ⅱ+1.13 Ⅲ+2.13 Ⅳ。与期望染色体配对模式相比,双二倍体中二价体出现的频率有明显增大的趋势。在减数分裂AⅠ和AⅡ分别观察到数目不定的落后单价体,大部份的四分体中出现了微核。双二倍体的育性得到了很大程度的恢复,其花粉可染色性及结实率分别为54.4％和64.0％。     

Quantitative trait loci influencing β-glucan content in oat (Avena sativa, 2n=6x=42)

The β-glucan content of oat grain is of inter-est due to its positive human health role as a dietary component influencing serum cholesterol levels and its relation to the energy intake of livestock feed. Two recombinant inbred populations sharing a common parent (Kanota × Ogle and Kanota × Marion), and containing 137 individual lines each, were used to identify genomic regions that influence the β-glucan content in cultivated oat. Single-factor ANOVA, a backward elimination process, simple interval mapping (SIM) and simplified composite interval mapping (sCIM) were used to identify quantitative trait loci (QTLs). Regions on linkage groups 11 and 14 of the hexaploid oat RFLP map influenced β-glucan levels in both populations and over environments. Other genomic regions were identified whose effects varied depending on the genetic background, but were significant over measurements for a given population. Kanota and Ogle exhibit similar β-glucan levels and each parent contributed about the same number of positive β-glucan alleles in the Kanota × Ogle cross. Marion is higher in β-glucan content than Kanota and contributed all of the positive alleles in the Kanota × Marion cross. Three of the β-glucan QTL regions identified have been previously implicated as having a significant influence on the groat oil content in oat. These correlated QTL regions were either in coupling phase, with a region from one parent having the same effect on both traits, or were in repulsion phase. Identification of coupling- and repulsion-phase QTL regions for β-glucan and oil content facilitates the use of markers in manipulating these traits in oat breeding. Received: 8 September 1999 / Accepted: 25 March 2000     

Stabilities of lead(II) complexes formed in aqueous solution with methyl thiophosphate (MeOPS2–), uridine 5'-O-thiomonophosphate (UMPS2–) or adenosine 5'-O-thiomonophosphate (AMPS2–)

The acidity constants of twofold protonated methyl thiophosphate (MeOPS(2-)) and of monoprotonated uridine 5'- O-thiomonophosphate (UMPS(2-)) have been determined in aqueous solution (25 degrees C; I= 0.1 M, NaNO(3)) by potentiometric pH titration. The stability constants of their 1:1 complexes formed with Pb(2+), i.e. Pb(MeOPS) and Pb(UMPS), have also been measured. The results show that replacement of a phosphate oxygen by a sulfur atom increases the acidity by about 1.4 p K units. On the basis of recently established log versus plots ( = simple phosphate or phosphonate ligands where R is a non-coordinating residue), it is shown that the stability of the Pb(thiophosphate) complexes is by log Delta= 2.43+/-0.09 larger than expected for a Pb(2+)-phosphate interaction. The identity of the stability increase (log Delta) observed for Pb(MeOPS) and Pb(UMPS) shows that the nucleobase residue in the Pb(UMPS) complex has no influence on complex formation. To be able to carry out the mentioned comparisons, we have also determined the stability constant of the complex formed between Pb(2+) and methyl phosphate; the corresponding data for Pb(UMP) were already known from our earlier studies. The present results allow an evaluation of other Pb(2+) complexes formed with thiophosphate derivatives and they are applied now to the Pb(2+) complexes of adenosine 5'- O-thiomonophosphate (AMPS(2-)). The stability constants of the Pb(H;AMPS)(+) and Pb(AMPS) complexes were measured and it is shown that, within the error limits, the stability of the Pb(AMPS) complex is determined by the basicity of the thiophosphate group of AMPS(2-); in other words, no hint for macrochelate formation involving N7 was observed. More important, with the aid of micro-stability-constant considerations it is concluded that the structure of the dominating isomer of the Pb(H;AMPS)(+) species is the one where the proton is located at the N1 site of the adenine residue and Pb(2+) is coordinated to the deprotonated thiophosphate group. The insights gained from this study with regard to thiophosphate-altered single-stranded nucleic acids and their affinity towards Pb(2+) are discussed.     

Synthesis and characterization of [Pt(COD)Cl(NO3)] and [Pt(COD)(NO3)2] and the use of [Pt(COD)Clx(NO3)2−x] in the preparation of cis[Pt(PPh3)2Clx(NO3)2−x] (x=0, 1, 2) and [Pt(PPh3)3L](NO3) (L=Cl,NO3)

[Pt(COD)Cl₂] (COD=1,5-cyclooctadiene) is a versatile starting material for the synthesis of Pt(II) compounds. The preparations of the new compounds [Pt(COD)Cl(NO₃)], [Pt(COD)(NO₃)₂] and [Pt(PPh₃)₃(NO₃)](NO₃) and also of the known compounds cis[Pt(PPh₃)₂Cl₂], cis [Pt(PPh₃)₂Cl(NO₃)], cis[Pt(PPh₃)₂(NO₃)₂] and [Pt(PPh₃)₃Cl](NO₃)are reported. The compounds are characterized by elemental analysis, ³¹P{¹H} NMR spectroscopy and IR spectroscopy.