bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and Magnetization of (ND4)2Ni(SO4)2.6D2O And (NH4)2Ni(SO4)2.6H2O At 2-K by Neutron-Diffraction
Authors: Fender BEF , Figgis BN , Forsyth JB
Published: September 2010

The structure of (ND4)2Ni(SO4)2.6D2O has been determined at 2 K by means of neutron diffraction using two crystals, one mounted about the b axis and one about the c axis, in normal-beam Weissenberg geometry. Totals of 642 and 689 averaged unique reflections were obtained and refined together, allowing differing scale and extinction parameters, to give R(F2) = 0.053. The weighted average cell dimensions and atomic positional parameters are reported. The crystals are monoclinic, P21/a; a 9.073, b 12.305, c 6.255 Ǻ, β 106.9°. The structure is compared to that obtained by X-ray diffraction at c. 295 K. The similarity of the structure, including the hydrogen bonding, to that of the manganese compound, is very great, apart from the metal-oxygen bond lengths. The structure of (NH4)2Ni(SO4)2.6D2O was obtained by the study of one crystal mounted down the c axis, collecting only the hk0 and hk1 layers, also at 2 K. A total of 441 averaged unique reflections were obtained, and the structure refined to Rw(F2) = 0.043. Given the poor resolution in the c direction, the resultant structure is almost indistinguishable from that of the deuterated compound, except that the NiO6 octahedron seems more regular. The magnetization at 2.00 K and 4.60 T is shown to be in reasonable agreement with the value expected from the 90 K E.S.R . z.f.s . parameters, and the experimentally observed 8% difference between the deuterated and hydrogenous salts could well arise from a difference in z.f.s .parameters consequent upon the structural alterations.
Spin Spin Interactions in Polynuclear Nickel(II) Complexes. a Magnetic and Structural Study of Binuclear Nickel(II) Complexes of Enolic 1,3,5-Triketonates
Authors: Boyd PDW , Lee KS , Zvagulis M
Published: September 2010

The bulk magnetic susceptibilities of the binuclear nickel(II) complexes of the 1,3,5-triketonates from diethyl (2-oxocyclopentane- 1,3-diyl) bisglyoxylate (H2ecg) (1) and diethyl 2,4,6-trioxoheptanedioate (H2decg) (2) have been measured over the temperature range 6-300 K. Antiferromagnetic spin-spin coupling is observed in each case with Neel temperatures in the range 45-65 K. The X-ray crystal structure of [Ni( ecg )( py )2]2.( py ) has been solved. The complex crystallizes with one pyridine of solvation in the space group Pī [a 10.507(1), b 13.384(1), c 9.992(1) Ǻ, α 103.004(9), β 115.867(9), β 86.857(10)°, Z = 1]. The molecule is binuclear with two coplanar triketonate dianions bridging the two six-coordinate nickel atoms through a di-μ-oxo linkage [Ni-Ob-Ni angle 102.0(1)°]. Two pyridine molecules and four triketonate oxygen atoms are bound to each nickel atoms. Magnetostructural
correlations are presented in comparison with binuclear copper(II) 1,3,5-triketonates. The marked decrease in spin-spin interaction in the nickel complexes is attributed to increasing metal-bridging oxygen bond lengths that decrease the efficacy of the σ antiferromagnetic pathway xy||Ob||xy and contributions from the ferromagnetic xy||Ob||z2 pathway.
Synthesis and Substitution Stereochemistry of trans-Chlorobis(Ethylenediamine)-(Trifluoromethanesulfonato)Cobalt(III) Trifluoromethanesulfonate
Authors: Comba P , Curtis NJ , Jackson WG , Sargeson AM
Published: September 2010

The achiral green salt trans-[Co(en)2(O3SCF3) Cl ] CF3SO3 has been synthesized by controlled solvolysis of Λ- cis -or trans-[Co(en)2Cl2] Cl in CF3SO3H.Kinetic studies and proton n.m.r . and electronic absorption spectral data indicate that cis /trans isomerization of Co(en)2(O3SCF3) Cl+ in triflic acid is extremely rapid, and that the equilibrium strongly favours the trans geometry. The loss of the first Cl - from Co(en)2Cl2+ was too fast to measure (t1/2 < 1 s, -20°C, CF3SO3H), but the second Cl - was released at least 105-fold more slowly: k(3.5�0.1)x10-4 s-1, 25°C; ΔH 73.1�1.7kJ mol-1, ΔS - 66�5 J mol-1 K-1 in the range 30-60°C. Reasons for this enormous rate difference are discussed. Solvolysis of CF3SO3- from trans- Co(en)2(O3SCF3) Cl + was immeasurably rapid in H2O, dimethyl sulfoxide (Me2SO) and dimethylformamide (Me2NCHO) (t1/2 < 1 s, 25°C), but it was detectable in MeCN : k 5.0×10-2 s-1, 25°C. The steric course of substitution for these solvents has been determined spectrophotometrically , and by n.m.r . spectroscopy: 0.1 M HClO4, 40.5% cis - and 59.5% trans-Co(en)2(OH2)Cl2+; Me2SO, 77% cis - and 23% trans- Co(en)2(OSMe2)Cl2+; Me2NCHO, 73% cis - and 27% trans-Co(en)2(OCHNMe2)Cl2+; MeCN , 53% cis - and 47% trans-Co(en)2(NCMe2)Cl2+ (25°C). These results are discussed in the context of a wider body of data for the stereochemistry of substitution of trans- and cis -Co(en)2ClXn+ in H2O and non-aqueous solution, where a clear leaving group dependence emerges for the trans but not the as isomers. Finally, trans- [Co(en)2(O3SCF3) Cl ] CF3SO3 provides a useful synthetic route to cis- and trans-Co(en)2ClXn+ complexes.
Preparation, X-Ray Crystal-Structure and Properties of Pentacarbonyl-(Pyridinium-2-Thiolate)Tungsten(0)
Authors: Broomhead JA , Greenwood R , Pienkowski W , Sterns M
Published: September 2010

The title complex is prepared either photochemically from pyridine-2-thiol and W(CO)6 or thermally from WBr2(CO)4. The molecular structure of this air-stable, diamagnetic compound shows an octahedral environment for the metal. The ligand is sulfur-bound only and the pyridine nitrogen is protonated. Crystals are monoclinic, space group P21/c with a 722.8(1), b 1375.5(4), c 1306.7(2) pm, β 98.815(5)° V 1.2839(5)×109 pm3 and Z 4; 2294 data were refined to R 0.026, Rw 0.032.
Luminescence Probe Studies of Pyrene and Two Charged Derivatives in Nafion
Authors: Blatt E , Launikonis A , Mau AWH , Sasse WHF
Published: September 2010

The luminescence and absorption properties of pyrene, trimethylbyren-1-y1)ammonium chloride (tmpa) and sodium pyrene-1-sulfonate (sps) incorporated into the perfluorosulfonate membrane Nafion have been investigated. Addition of pb2+ induces a redistribution of pyrene molecules from the hydrophilic domains to more hydrophobic domains of the membrane and results in phosphorescence emission. tmpa is shown to bind strongly to the negatively charged sulfonate groups and does not exhibit phosphorescence nor is it displaced by pb2+. The fluorescence emission and absorption characteristics of sps incorporated in Nafion suggest a hydrophilic microenvironment, probably the water cluster region. The electrostatically unfavourable interaction, however, results in excimer formation even at low probe concentrations. Dynamic and steady-state fluorescence quenching measurements provide further insight into the nature of the different regions of Nafion.
Organolanthanoids. XI. The Crystal and Molecular Structures of Two Tris(η5-cyclopentadienyl)(pyridine) lanthanoid(III) Compounds
Authors: Deacon GB , Gatehouse BM , Platts SN , Wilkinson DL
Published: September 2010

The crystal structures of tris (η5-cyclopentadienyl) (pyridine) samarium(III), monoclinic, space group P21/c, a 10.906(4), b 8.636(2), c 17.825(3) �, β 96.44(2)�, Z 4, R 0.027 and Rw 0.032 for 3619 'observed' reflections, and tris (η5-cyclopentadienyl)(pyridine)neodymium(III), monoclinic, space group P21 / c, a 14-206(4), b 8.619(2), c 15.190(7) �, β 107.38(2)�, Z 4, R 0.035 and R, 0.039 for 2677 'observed' reflections have been determined. Both compounds have pseudotetrahedral geometry with a coordination number of 10 for the lanthanoid metal but there is a difference in the coordination of pyridine and in unit cell packing between the two structures.
The Structure of Papaverine in Solution as Determined by 1H Nuclear Magnetic Relaxation Methods
Authors: Rae ID , Rae ID , Simmonds PM , Simmonds PM
Published: September 2010

Hydrogen relaxation in the papaverine molecule in CDCl3 solution has been studied so as to derive the conformation about the C1-CH2 bond. This was done for papaverine itself, in which the resonances of H5 and H8 were reassigned on the basis of NOESY spectra, and in the 7-OC2H3 analogue, the spectrum of which confirms the reassignment. The value for the torsional angle C 8a-C1-CH2-C lays between 70 and 92�, in good agreement with those found in crystals of papaverine , its hydrochloride, and the related alkaloid isosevanine (all in the range 68-94�). Conformational energy calculations show a broad energy minimum over the range 60-70�. The 6,7-methylenedioxy analogue of papaverine has essentially the same conformation but tumbles more rapidly in solution, the Tc value for it being 1.9×10-1ls whereas values for papaverine were 5.6×10-11 s (from 1H relaxation) and 3.1×1011 s (from 13C relaxation).
The Crystal Structure of catena-{μ-[2-Methyl-2-(phenylthio)propanoato-O,O′]-{tris-μ-[2-methyl-2 -(phenylthio)propanoato-O,O′]-dizinc(II)}}
Authors: Chan WH , Mak TCW , Yip WH , Kennard CHL , Smith G , Oreilly EJ
Published: September 2010

.The crystal structure of
the anhydrous zinc(11) complex of 2-methyl-2-(phenylthio) propanoic acid, with formula [Zn2(C10H12O2)4]n, has been determined by X-ray diffraction at 20�C and refined to a residual R 0.041 for 2885 observed reflections. Crystals are monoclinic, space group P 21, with two diper units of the polymer in a unit cell with dimensions a 12.710(4), b 13.760(2), c 12.699(6) �, β 95.44(5)�. The polymer structure is based on a repeating tris -carboxylate-bridged dimer unit with each zinc centre tetrahedral [Zn-O (mean) 1.958(5) �, Zn-Zn 3.393(2) �]. The dimer is extended into a linear polymer chain by an O,O' bridge through the carboxy group of the fourth carboxylate ligand.
Lewis-Base Adducts of Group I Metal(I) Compounds. XXVI. Solid-State Cross-Polarization Magic-Angle-Spinning 31P N.M.R. and Structural Studies on 1:1 Adducts of Triphenylphosphine With Gold(I) Salts
Authors: Barron PF , Engelhardt LM , Healy PC , Oddy J , White AH
Published: September 2010

Linear, two-coordinate compounds of molecular formula (PPh3) AuX have been characterized by solid-state and solution 31P n.m.r. spectroscopy, and single-crystal X-ray diffraction techniques. The solid state n.m.r. spectra reveal single, broad resonance lines for X = NO3 (chemical shift 19 ppm , ref. 85% H3PO4), CH3C02 (24 ppm), SCN (36ppm), CN (37 ppm ) and CH3 (47 ppm ) and doublets for X = Cl (27, 33 ppm ), Br (28, 36 ppm ) and I (34, 38 ppm ), the latter three spectra being recorded at 121.47 MHz and 161.96 MHz. Solution spectra show relatively sharp single resonances for each compound with 6 values generally slightly higher than in the solid state. Crystal data are reported for X = NO3, space gro )p P21/c, a 8 895(9), b 10.117(8), c 19.57(2) �; β 97.43(8)�, Au-P,O = 2.199(5), 2.02(1) �. Crystals of compounds with X = Br, I and SCN are isomorphous with the AuCl compound, belonging to space group 212121. For X = Br, a 12.479(5), b 13.45(1), c 10.0!2(8) �; Au-P, Br = 2.252(6), 2.407(2) �. For X = I, a 12.529(8), b 13.870(5), c 10.188(4) �; Au-P, I = 2.254(5), 2.556(2) �. For X = SCN, a 12.257(5), b 13.776(8), c 10.754(6) �; Au-P, S = 2.252(7), 2.304(7) �.
A New Synthesis of 3,4-Dihydro-β-Carboline (3,4-Dihydro-9h-pyrido[3,4-B]indole)
Authors: Maclaren JA
Published: September 2010

The enamine derived from tryptamine and ethyl ethoxymethylenemalonate, on treatment with trifluoroacetic acid or boron trifluoride, is converted into 3,4-dihydro-β-carboline.
New Macrocyclic Ligands. Synthesis of an Extensive Series of Potentially Pentadentate Ligands Containing Mixed Nitrogen, Oxygen and or Sulfur Heteroatoms. The X-Ray Structure of an O2N2S Derivative
Authors: Baldwin D , Duckworth PA , Erickson GR , Lindoy LF , Mcpartlin M , Mockler GM , Moody WE , Tasker PA
Published: September 2010

The syntheses of 16 new 16- to 19-membered dibenzo macrocycles are reported. These rings incorporate nitrogen together with oxygen and/or sulfur heteroatoms . The X-ray structure of the 17-membered macrocycle containing an O2N2S heteroatom set is described.
Through-Space Transmission of 19F-13C Coupling Via an Intermediate Bond. An Experimental and Theoretical Study
Authors: Rae ID , Rae ID , Staffa A , Staffa A , Diz AC , Diz AC , Giribet CG , Giribet CG , Deazua MCR , Deazua MCR , Contreras RH , Contreras RH
Published: September 2010

In order to obtain a deeper insight into the title effect, several compounds with an F atom very close to a C-H of a nearby functional group were synthesized and the relevant couplings measured. The most conspicuous case was that of 8-fluoro-2-hydroxynaphthalene-1-carbaldehyde where a close proximity between the F and H atoms is the result of fluorine-oxygen repulsion and the formation of an intramolecular hydrogen bond between the hydroxyl and carbonyl groups. The experimental four-bond J(F,CHO) coupling is 26.2 Hz. A compound very similar to this one, but without the OH group, was chosen on which to perform a polarization propagator analysis of the through-space (TS) coupling pathways, at the RPA-INDO level. The expression for the TS coupling in terms of the projected polarization propagator and perturbators was numerically analysed. It is found that this coupling is completely dominated by a TS component of the Fermi contact (FC) term, the main features of which are: ( i ) It decays exponentially with the F-H distance; (ii) Its main contribution comes from an electron excitation involving the F lone-pair, the C-H bond of the CHO moiety and its corresponding antibonding orbital;(iii) The π-type lone-pair does not contribute to the TS coupling pathway of the FC term.
Aluminum-Tannin Equilibria: A Potentiometric Study
Authors: Kipton H , Powell J , Rate AW
Published: September 2010

The equilibrium reactions between aluminium(III) and an epicatechin polymer or tannin (T) have been studied by potentiometric titration at 25�C, I = 0.001 M. The tannin, which has on average ten 1,2-dihydroxybenzene units per molecule, encapsulates the aluminium ion to form a bis(l,2-diphenolato) complex at pH 5-7. Stability constants are reported for Al(TH-2) (logK11-2, -3.95 � 0.05), Al(TH-3) (logK11-3, -4.5 � 0.1) and Al(TH-4) (logKl1-4, -5.7 � 0.2). A small chelate effect arising from coordination of remote pairs of 1,2-diphenolato groups was observed.
Structure, Stereochemistry and Novel 'Hydrogen Bonding' in Two Bipyridinium Salts of the B10H102- Anion
Authors: Fuller DJ , Kepert DL , Skelton BW , White AH
Published: September 2010

Crystal structure determinations of (LH)2(B10H10), (1), and (LH2)(B10H10), (2), L = 2,2'- bipyridine , have been carried out by single-crystal X-ray diffraction methods at 295 K, being refined by full-matrix least squares to residuals of 0.041, 0.047 for 1758, 1771 'observed' independent reflections respectively. Crystals of (1) are monoclinic, P21/n, a 12.040(7), b 17.71(1), c 11.142(4) �, β 101.78(4)�, Z 4. Crystals of (2) are monoclinic, P21/c, a 9.937(4), b 10.837(3), c 14.856(5) �, β 109 2l(3)�, Z 4. The colour of the compounds is accounted for by charge-transfer interactions of a novel type, namely between the positively charged cationic acid hydrogen atoms and the negatively charged non-apical hydrogen atoms of the anion. In yellow (1), these distances are 2.26(5) �, while in red (2), they are much shorter, being 1.89(4), 1.97(3) �.
Selective Sulfonylating Agents
Authors: Guthrie RD , Thang S
Published: September 2010

A variety of bulky sulfonyl chlorides have been investigated as sulfonylating reagents for polyol systems in an endeavour to find a selective reagent that would also give rise to a reactive sulfonate ester group.
Heterocyclic Tautomerism. IV. The Solution and Crystal Structures of 1-Aryl-3-phenyl-1,2,4-triazol-5-ones
Authors: Rae AD , Ramsay CG , Steel PJ
Published: September 2010

The title compounds are shown to exist in solution and in the solid state as 4H-tautomers. X-Ray crystal structure determinations show that 1,3-diphenyl-1,2,4-triazol-5-one exists as a dimeric pair of strongly hydrogen-bonded molecules and that 3-phenyl-1-(2-pyridyl)-1,2,4- triazol-5-one exists as the 4H-tautomer stabilized by a complex network of hydrogen bonding to water molecules.
Oxidation of Formatopentaamminecobalt(III) Perchlorate by Silver(II)
Authors: Creaser II , Lancaster MJ , Lawrance GA , Sargeson AM , Sullivan JC
Published: September 2010

Formatopentaamminecobalt (III) perchlorate is oxidized relatively rapidly by AgO in acid conditions (1 M H2SO4, HNO3 or HO3SCF3), with approximately 97% of the total cobalt retained in the cobalt(III) state as [Co(NH3)5(OH2)]3+ and [Co(NH3)5X]n+ (X = SO42- or NO3-). A combination of product distribution, silver(I) and silver(II) concentration dependence and 18O-labelling experiments indicate that the major pathway (97%) is oxidation of [Co(NH3)5(OCHO)]2+ directly to [(NH3)5Co(OCO)]3+ and [(NH3)5Co(O2COH)]2+ by AgIII (through the disproportionation 2AgII ↔ AgIII + AgI ) in a relatively rapid hydride extraction. A minor path (3%) appears to involve a one-electron oxidation by AgII to the complexed radical anion [(NH3)5Co(OC?O)]2+ which then decays intramolecularly to yield CoII and CO2. In 1 M H2SO4 the cobalt(III) intermediate, [(NH3)5Co(OCO)]3+, has been shown by 18O-labelling and competition experiments to decay by dissociation into [Co(NH3)5]3+ and CO2. The pentacoordinate intermediate [Co(NH3)5]3+ immediately captures OH2 and HSO4-.
Electronic-Transitions in the Near-Ultraviolet Spectra of Uracil, Thymine, Uridylyl(3'-5')uridine and Thymidylyl(3'-5')thymidine
Authors: Connell KE , Kurucsev T , Norden B
Published: September 2010

The absorption spectra in the near-ultraviolet region of uracil and thymine, and of their derivatives may be deconvoluted into two vibronic progressions; the higher-energy progression has a relatively low intensity. The corresponding component spectra coincide with the two separate transitions manifested in the circular dichroism of the relevant nucleoside derivatives. A series of apparent contradictions may be resolved by the assumption that the higher-energy transition in absorption is a vibronically allowed (π*,n) transition. This interpretation is further supported by an analysis of the spectra of uridylyl (3′-5′) uridine and thimidylyl (3′-5′) thymidine in terms of exciton interactions. The magnitude of exciton coupling in the dinucleoside phosphates is found to be small but significant in terms of energy transfer rates.
Asymmetric Hydrocyanation of a Range of Aromatic and Aliphatic Aldehydes
Authors: Matthews BR , Jackson WR , Jayatilake GS , Wilshire C , Jacobs HA
Published: September 2010

A range of aryl, alkyl and heterocyclic aldehydes have been treated with hydrogen cyanide in the presence of the 'Inoue' catalyst, (R,R)- or (S,S)-cyclo [phenylalanylhistidyl]. Most aryl aldehydes with electron-donating substituents in the m- or p-positions give high enantiomeric excess (e.e.) values (≥80%) but aryl aldehydes with strong electron-withdrawing substituents gave moderate e.e. values (≤50%). These moderate values are believed to be due to partial racemization of the product cyanohydrins in the presence of the mildly basic catalyst. In contrast to the reactions of aryl aldehydes , reactions of alkyl aldehydes and of ketones gave low e.e. values (≤30%) and an explanation is proposed.
Palladium-Mediated Transformations of Heteroaromatic Triflates
Authors: Crisp GT , Papadopoulos S
Published: September 2010

Quinolyl triflates and isoquinolyl triflates undergo palladium-catalysed couplings with organostannanes, organoaluminiums and activated alkenes. The range of organic groups which can be transferred to the heteroaromatic substrate includes aryl, vinyl, alkynyl, alkyl and hydride.
15N Nuclear Magnetic-Resonance Spectra of ortho-Substituted Phenylacetanilides: The Origin of γ-syn Effects
Authors: Yamagami C , Takao N , Takeuchi Y
Published: September 2010

The 15N chemical shifts of X α and Y α, i.e., the nuclei through which the side chains, X and Y, respectively, of o-substituted phenylacetanilides (2a) are bonded to the aromatic ring were determined. There was observed a uniform upfield shift (γsyn effect). In order to explore the origin of the γ effect, other o-disubstitutes benzenes (2b-d) were also examined. The values of D, defined as the difference between γ α substituent chemical shifts of the ortho (2) and para (3) series of compounds, and considered as a measure of the γ-syn effect, were correlated with various electronic and steric substituent parameters. Correlations with electronegativity and van der Waals terms were successful. Examination of the correlations indicated that the γ-syn effect is mostly governed by electronegativity. The classic steric compression theory does not seem very convincing as a means of explaining the shielding γ-syn effect observed in the present study.
Vibrational Band Origins of 7Li26Li+ and 6Li27Li+
Authors: Searles DJ , Vonnagyfelsobuki EI
Published: September 2010

The vibrational band origins of 7Li3+, 7Li26Li+ and 6Li27Li+ were calculated by using the t-coordinate vibrational Hamiltonian of Carney et al. The results for 7Li3+ and 7Li26Li+agree with those of Henderson et al.obtained by using a body-fixed scattering coordinate Hamiltonian. No vibrational band origins for 6Li27Li+ have so far been reported.
Studies of Australian Soft Corals. XLIV. New Diterpenes From Sinularia polydactyla (Coelenterata, Anthozoa, Octocorallia)
Authors: Bowden BF , Coll JC , Wright AD
Published: September 2010

The soft coral Sinularia polydactyla has yielded six highly functionalized diterpenes. The known diterpenes pukalide (2) and 1-epithunbergol (3) were readily identified by spectral comparison with authentic samples. The new natural products 13 α-acetoxy-11β, 12β-epoxypukalide (4),13 α-acetoxypukalide (5) and its allylically rearranged isomer (6) were identified on the basis of 2D-n.m.r. experiments at 300 MHz and by spectral comparison with the known compounds pukalide (21, lophotoxin (8) and epoxypukalide (9). A minor, relatively unstable metabolite (7) is tentatively identified as a 3,4:5,6-bisepoxy derivative of (6). The biological implications of these findings are discussed.
Synthesis and X-Ray Structure of syn-Di-μ-thio-bis[(N,N-diethyldithiocarbamato-S,S')oxotungsten(V)]
Authors: Mackay MF , Oliver PJ , Young CG
Published: September 2010

The reaction of WSCl4 and Me3SiS2CNEt2 in tetrahydrofuran produces a green solid which yields WS(S2)(S2CNEt2)2, WO(S2)(S2CNEt2)2 and syn-W2O2( �-S)2(S2CNEt2)2 upon exposure to oxygen. Crystals of syn-W2O2( �-S)2(S2CNEt2)2 are monoclinic and belong to space group C2/c with a 33.880(4), b 7.012(1), c 18.072(1) � ,β 105.94(1)� and Z 8. Refinement on 2651 data measured with Cu K α: radiation converged at R 0.070. The complex possesses a syn-[W2O2(�-S)2]2+ core with a W-W bond [2.808(1) � ] and two terminal W-O bonds [1.66(2) and 1.68(2) � ]. The W-S(bridging) bond distances are in the range 2.319(5)-2.3346) � Each of the square-pyramidal tungsten atoms is further coordinated to a bidentate dithiocarbamate ligand with W-S bond distances ranging from 2.447(6) to 2.459(5) � .
Organolanthanoids. XV. The Preparation of Carboxylatobis(cyclopentadienyl)ytterbium(III) Complexes by Oxidation of Bis(cyclopentadienyl)ytterbium(II)
Authors: Deacon GB , Wilkinson DL
Published: September 2010

The complexes, Cp2Yb(O2CR) [Cp = cyclopentadienyl; R = Me, CF3, Ph, C6F5, C6Br5, o- MeO2CC6F4 (tmcp), 2,4,6-Me3C6H2 (tmp), pyridin-2-yl (pyr), or quinolin-2-yl (quin)] have been prepared in good yield by oxidation of bis(cyclopentadienyl)(1,2-dimethoxyethane)ytterbium(II) with the appropriate mercury(ll) or thallium(I) carboxylate, generally in tetrahydrofuran. Structural data suggest that four complexes (R=Me, CF3, Ph or C6F5) are dimeric with bridging bidentate carboxylate groups, three (R = tmp, pyr or quin) are monomeric with chelating carboxylates, but the structure is less clear for R = C6Br5 or tmcp. Unit cell dimensions have been determined for bis(cyclopentadienyl)(2,4,6-trimethyibenzoato)ytterbium(III), but the structure could not be solved owing to decomposition of single crystals in the X-ray beam.
Solid-State 31P N.M.R. Spectra of (PPh3)( bpy )CuCl
Authors: Healy PC , Kildea JD
Published: September 2010

Solid-state cross-polarization magic-angle-spinning 31P n.m.r. spectroscopy has been used to assign conformational structure to (PPh3)( bpy )CuCl.
The Crystal-Structure of Tetraphenylarsonium Tetrachlorooxotechnetate(V)
Authors: Baldas J , Colmanet SF
Published: September 2010

The crystal structure of [AsPh4] [TcOCl4] (1) has been determined by X-ray diffraction. Crystals are tetragonal, space group P4/n, a 12.664(1), c 7.822(1) � , Z = 2. Refinement based on 912 data measured with Cu Ka radiation converged with R 0.059. The structure consists of discrete [AsPh4]+ cations and [TcOCl4]- anions with the technetium atom in a square-pyramidal environment. In contrast to an earlier structural determination of the [TcOCl]-anion in [N(PPh3)2] [TcOCl4], the [TcOCl4]-anion in (1) possesses ideal symmetry. The Tc =O bond length is 1.593(8) � with Tc -CI 2.309(2) �.
Preparation of Some 9-Hydroxy-2-oxaspiro[4.5]dec-8-ene-1,7-dione Derivatives by Reductive Alkylation of 3,5-Dimethoxybenzoic Acid With 1,2-Dihaloalkane and Oxiran Electrophiles
Authors: Wilkie JS , Winzenberg KN
Published: September 2010

Lithium in liquid ammonia mediated reductive alkylation of 3,5-dimethoxybenzoic acid (3) with 1,2-dibromoethane, or 1-bromo-2-chloroethane, followed by acid hydrolysis, afforded 9-hydroxy-2-oxaspiro[4.5]dec-8-ene-1,7-dione (1a). Reductive alkylation of (3) with unbranched 1,2-dibromoaikanes (5b-g), 1,2-dibromo-3-methylbutane and 1,2-dibromo-3,3-dimethylbutane gave 3-alkyl-9-hydroxy-2-oxaspiro[4.5]dec-8-ene-1,7-dione derivatives (1b-i) in moderate yields with the exception of (1i). The major product of the last reaction was 1-(2-bromo-3,3- dimethylbutyl )-3-hydroxy-5-oxocyclohex-3-ene-1-carboxylic acid (9). No reductive alkylation of (3) was observed with 2,3-dibromobutane or 1,2-dibromo-2methylpropane. Reductive alkylation of (3) with the oxiran derivatives (8a-d) afforded the 2-oxaspiro[4.5]dec-8-ene-1,7- dione derivatives (1a-c,j). Reductive alkylation of (3) with 1,3-dibromopropane and l-bromo-3-chloropropane gave, after hydrolysis, 1-(3-bromopropyl)-3-hydroxy-5-oxocyclohex-3-ene-l- carboxylic acid (12a) and 1-(3-chloropropyl)-3-hydroxy-5-oxocyclohex-3-ene-1-carboxylic acid (12b). The conversion of (1a) into 8-[1-( ethoxyimino )butyl]-9-hydroxy-2-oxaspiro[4.5]dec-8-ene-1,7-dione (2a) is described.
Constituents of Millingtonia hortensis: Isolation and Crystal Structure of trans-1-(2'-Hydroxyethyl)cyclohexane-1,4-diol
Authors: Naowsaran K , Skelton BW , Tooptakong U , Tuntiwachwuttikul P , White AH
Published: September 2010

The isolation of trans-1-(2'-hydroxyethyl)cyclohexane-1,4-diol from the flowers of Millingtonia hortensis and its characterization, including a single-crystal X-ray structure determination at 295 K, is described. Crystals are triclinic, P1, a 12.348(5), b 11 .390(5), c 6.575(3) � , α 112.16(3), β 90.79(4), γ°, Z 4. R was 0.045 for 1475 independent 'observed', diffractometer reflections. In the two independent molecules of the asymmetric unit, the cyclohexane ring is in the usual 'chair' conformation with the ring hydroxy substituents occupying axial positions. The hydroxyethyl groups, however, adopt different orientations in the two molecules.
Caveat Regarding the Use of Substituent Parameters in Statistical Analyses of Molecular Properties. II. Case Study : 13 N.M.R. of 2-Substituted Pyridines and Monosubstituted Benzenes
Authors: Cook IB
Published: September 2010

Carbon-13 n.m.r. substituent chemical shifts of equivalent positions on monosubstituted benzenes and 2-substituted pyridines are analysed by multiple linear regression on combinations of a field, resonance, electronegativity and three polarizability parameters. The ortho and meta positions of the 2-pyridine and benzene series are poorly described by σF and σR parameters, but a much improved fit is obtained when σx and/or a bond polarizability parameter σ α,(C-X) are included. The mechanism of shift formation differs markedly between the two systems when the C2, C4 and C6 positions on pyridine are compared with the geometrically equivalent positions on benzenes. Owing to the high degree of interdependence between the four substituent effects, quantitative analysis proved to be impossible. However, use of subsets of substituents with three of the four parameters approximately orthogonal enabled the mechanism to be deduced in most cases. It is postulated that the differences between the pyridine and benzene systems arises from perturbation of the C-N bond polarity. A mechanism to explain the results is presented.
Synthesis of O-Phosphotyrosine-Containing Peptides. II. Solution-Phase Synthesis of Asn-Glu-PTyr-Thr-Ala Through Methyl Phosphate Protection
Authors: Valerio RM , Perich JW , Kitas EA , Alewood PF , Johns RB
Published: September 2010

The PTyr (O-phosphotyrosine) pentapeptide H-Asn-Glu-Tyr(PO3H2)-Thr-Ala-OH.HO2CCF3, which is a naturally occurring sequence from the autophosphorylated Rous sarcoma virus pp60V-SrC, was prepared in high yield by the use of Boc-Tyr(PO3Me2)-OH in the Boc mode of solution-phase peptide synthesis. The protected pentapeptide, Z-Asn-Glu(OBzl)-Tyr(PO3Me2)-Thr(Bzl)-Ala-OBzl, was deprotected by a two-stage procedure which involved initial palladium-catalysed hydrogenolysis followed by the removal of the phosphate methyl groups by the use of one of the following treatments: (A) 10% bromotrimethylsilane/acetonitrile, (B) 1 M bromotrimethylsilane/thioanisole in trifluoroacetic acid, or (C) trifluoromethanesulfonic acid/trifluoroacetic acid/dimethyl sulfide/m-cresol.
Imidazo[1,2-b]Pyridazines. VI. Syntheses and Central Nervous System Activities of Some 6-(Alkoxy- and Methylthio-phenoxy and Methoxybenzylthio)-3-methoxy-2-phenyl(substituted phenyl and pyridinyl)Imidazo[1,2-b]pyridazines
Authors: Barlin GB , Davies LP , Ireland SJ , Ngu MML
Published: September 2010

Series of 6-( alkoxy - and methylthio-phenoxy )-2-phenyl(substituted phenyl and pyridiny1)imidazo[l,2-b]pyridazines and 3-methoxy-6-( methoxybenzylthio )-2-phenyl(substituted phenyl and pyridinyl ) imidazo[l,2-b]pyridazines have been prepared and subsequently tested for their ability to inhibit GABA-stimulated 3H-diazepam binding to rat brain plasma membranes. The 6( alkoxy- and methylthio-phenoxy ) and 6-( methoxybenzylthio) compounds were much more effective in the displacement studies than the parent 6-phenoxy or 6-benzylthio compounds respectively. 3-Methoxy-6-(2′-methoxyphenoxy)-2-phenylimidazo[l,2-b]pyridazine (GBLD-167, IC50 70 nm) was 16 times more effective than its 3-methoxy-6-phenoxy analogue (GBLD-163, IC50 1120 nM ) and the 3-methoxy-6-(21-methoxybenzylthio)-2-phenyl compound (GELD-214, 1C50 9 nM ) was two and a half times more active than its 6-benzylthio-3-methoxy analogue (GBLD-137, IC50 22 nM ). The most active member of the 6-phenoxy series was the 2-(41-fluorophenyl)-3-methoxy-6- (2″-methoxyphenoxy) compound (GBLD-255, IC50 30 nM ) and, within the 6-benzylthio series, the 2-(4′-fluorophenyl, 3′-aminophenyl, and pyridin-31-yl)-3-methoxy-6-(3″-methoxybenzylthio) compounds (GBLD-233, 301 and 296) all gave IC50 5 nM. A Hansch -type analysis of the results for these two closely related series of compounds indicates that electron-donating substituents in 2-(para substituted phenyl) derivatives favour binding, but bulky substituents hinder this effect.
Synthesis and Conformational Analysis of the Slime-Mold Acrasin Glorin
Authors: Ball JB , Craik DJ , Alewood PF , Morrison S , Andrews PR , Nicholls IA
Published: September 2010

The chemotactic dipeptide for the slime-mould Polysphondylium violaceum, glorin (N- propionyl-y-L-glutamyl-L-ornithine-δ-lac ethyl ester) (8), was synthesized convergently in five steps with 41% overall yield, starting from L- ornithine hydrochloride (1) and L- glutamic acid γ-benzyl ester (4). -1H n.m.r. spectral analysis led to the conclusion that the propionamide and the γ-L- glutamyl amide bonds both undergo slow cis-trans isomerism in solution at room temperature. From a Karplus-type analysis of the values of the Cα,Cβ coupling constants at the lactam chiral carbon, it was concluded that the six-membered ring can adopt either a half-chair or half-boat conformation, but it is not clear which. Similar calculations for the glutamyl Ca,Cβ coupling constants were performed and, from these, significantly different relative populations for the three staggered conformations about the Glu-Ca,Cβ bond were suggested. Receptor binding studies showed that glorin did not bind significantly to any of the six receptors studied, including opioid, dopamine, central benzodiazepine, peripheral benzodiazepine, α1-adrenoceptor and α2-adrenoceptor sites.
1H-N.M.R. and Theoretical Studies of the Conformation of the Antibiotic Lincomycin
Authors: Moloney GP , Craik DJ , Iskander MN , Munro SLA
Published: September 2010

One- and two-dimensional 1H n.m.r. spectra of the amino glycoside antibiotic lincomycin have been measured and analysed. One-dimensional n.m.r. techniques applied included selective decoupling, resolution enhancement, and n.O.e. difference experiments. Two-dimensional n.m.r. techniques included chemical shift correlated spectroscopy (COSY) and n.O.e. spectroscopy (NOESY) experiments. A theoretical conformational analysis of the side chain of the sugar moiety has also been done by using a simplified potential energy program. Together, the theoretical and experimental (coupling constant and n.O.e.) data have allowed the conformation of lincomycin to be determined.
Epoxy Lipids From the Australian Epiphytic Brown Alga Notheia anomala
Authors: Barrow RA , Capon RJ
Published: September 2010

A detailed reinvestigation of the chemistry of Notheia anomala has resulted in the isolation of the known C19 lipid (1) together with 13 new C19 lipids (2), (3), (3a,b,c) (4), (4a,b,c) (8), (10),(13) and (14), one new C21 lipid (15) and two known C21 lipids, (17) and (18), and a new C17 lipid (19). The structures of these metabolites were established by spectroscopic analysis together with chemical derivatization and degradation. Absolute stereochemistries were determined by chemical and biosynthetic correlation to (1). A common biosynthetic pathway is proposed for all the oxygenated lipids from N. Anomala.
Crystal Structure of Two Different Hydrate Phases of Bis[2,4,6-tri(2-pyridyl)-1,3,5-triazine]cobalt(II) Diiodide
Authors: Figgis BN , Kucharski ES , Mitra S , Skelton BW , White AH
Published: September 2010

The title compound crystallizes at room temperature from aqueous solution as two distinct hydrated phases, both monoclinic and characterized by single-crystal X-ray structure determinations. The dihydrate ('blocks') is C2/c, a 42.58(2), b 9.099(8), c 21.14(1)Ǻ, β 112.12(4)°, Z= 8; R was 0.048 for 3784 'observed' reflections. The c. 3.75 hydrate ('Tetrahydrate'?) ('needles') is P21/c, a 9.348(2), b 36.663(8), c 23.071(8)Ǻ, β 93.51(2)°, Z 8; R was 0.050 for 6042 'observed' reflections. There are one and two independent cations in the asymmetric unit of each structure; all cations have the metal atom 'mer' coordinated by a pair of tridentate ligands. In the C2/c phase, Co-N (central) are 2.057(4) and 2.063(4)Ǻ with N-Co-N 175.8(2)°; Co-N (distal) are 2.163(6)-2.187(6)Ǻ. In the P21/c phase, in the first cation, Co-N are 2.045(8) and 2.050(7)Ǻ (central) [with N-Co-N, 167.0(3)°] and 2.193(8)-2.216(8)Ǻ (distal), while, in the second, Co-N (central) are 2.030(8) and 2.042(8)Ǻ with N-Co-N, 168.3(3)°; Co-N (distal) are 2.164(8)-2.227(8)Ǻ. These Co-N distances are longer than those observed in the [Co( tpy )2]2+ cations hitherto studied ( tpy = 2,2′:6′,2′-terpyridine), in which the electronic ground state has an appreciable low-spin component.
The Phthalimidomethyl Rearrangement
Authors: Wilshire JFK
Published: September 2010

The discovery of a new acid-catalysed monodentate N → C aromatic rearrangement, namely the phthalimidomethyl rearrangement, is reported. In this rearrangement, discovered during the reaction of N-hydroxymethylphthalimide with certain alkyl N-(4-nitrophenyl)carbamates in concentrated sulfuric acid solution, the phthalimidomethyl group migrates from its initial location on the nitrogen atom of the carbamate function to a carbon atom of the nitrophenyl group. Evidence, provided by an appropriate 'crossover' experiment, indicates that the rearrangement is intermolecular. Hindered rotation about the N(carbamoyl)-aryl bond of the N-phthalimidomethyl derivatives of both ethyl and methyl N-(2,4-dinitrophenyl)carbamate is reported.
2,6-Dimethylbicyclo(3.3.1)nona-3,7-diene-endo-2,endo-6-diol, an Alicyclic Diol Whose Crystal-Structure Involves Two Types of Hydrogen-Bonded Columns
Authors: Mallick MAI , Bishop R , Craig DC , Dance IG , Scudder ML
Published: September 2010

The crystal structure [C11H16O2, C2/c, a 32.19(1), b 7.648(1), c 20.101(8)Ǻ, β 126.63(1)°, Z 16] of 2,6-dimethylbicyclo[3.3.1] nona 3,7-diene-endo-2,endo-6-diol (7) was determined with final R 0.041. This structure is unlike the helical and layer arrangements reported earlier for related alicyclic diols with C2 symmetry, and is constructed from two types of double-stranded columns of diol molecules.
Surfactant Inclusions by Modified β-Cyclodextrins
Authors: Lavandier CD , Pelletier MP , Reinsborough VC
Published: September 2010

Binding constants for the inclusion of sodium alkane-1-sulfonates (C5-C10, C12) by four modified β- cyclodextrins (2,6-O-dimethyl-β-cyclodextrin, 2,3,6-O-trimethyl-β-cyclodextrin, hydroxypropyl-β-cyclodextrin and maltosyl-β-cyclodextrin ) were determined conductimetrically at 25°C. Binding increased with increasing length of the alkyl chain. Generally, the substituted β- cyclodextrins were no more effective as encapsulating agents than ordinary β- cyclodextrin with the persubstituted 2,3,6-O-trimethyl-β-cyclodextrin being the weakest.
Thermal Dehydrochlorination of Poly(vinyl chloride) Model Compounds. II. Computer Analysis of Kinetic Results
Authors: Boughdady NM , Chynoweth KR , Hewitt DG
Published: September 2010

Computer simulation has been used to analyse the condensed-phase thermal degradation of a series of compounds with functional groups related to defects found in poly(vinyl chloride) ( pvc ). We have been able to estimate the relative significance of catalysed and non- catalysed processes and make some estimates of the significance of allylic rearrangement.
Cytotoxic and Antifungal C14 Amines From a New Zealand Ascidian: Major Lipid Components of Pseudodistoma novaezelandiae
Authors: Perry NB , Blunt JW , Munro MHG
Published: September 2010

The principal cytotoxic and antifungal components of the compound ascidian Pseudodistoma novaezelandiae were the C14 triene amines (3) and (4). These compounds were major lipid components, present at similar levels to fatty acids and sterols. C12 and C14 diene amines (5) and (6) were also present at lower levels.
Iron(II) and Nickel(II) Complexes of 2,6-Di(thiazol-2-yl)pyridine and Related Ligands
Authors: Baker AT , Singh P , Vignevich V
Published: September 2010

2,6-Di(thiazol-2-yl]pyridine (1a), 2,6-di(4-methylthiazol-2-yl)pyridine (1b) and 2,6-di(2-imid-azolin-2-yl)pyridine (3) have been prepared by the reaction of pyridine-2,6-dicarbothioamide with bromoacetaldehyde diethyl acetal, bromoacetone and ethylenediamine, severally. Bis ( ligand )
iron(II) and nickel(II) complexes of all ligands have been prepared. The bis ( ligand ) iron(II) complexes of (1a) and (3) are low-spin whereas that of (1b) is high-spin at room temperature and undergoes a thermally induced spin transition. The field strengths of the ligands , determined from the spectra of their nickel(II) complexes, correlate well with the observed magnetic behaviour of their iron(II) complexes. The field strengths of (1a) and (1b) are found to be marginally less than those of the isomeric ligands 2,6-di(thiazol-4-yl)pyridine (2a) and 2,6-di(2-methylthiazol-4-yl)pyridine (2b).
Lewis-Base Adducts of Groups 11 Metal(I) Compounds. LXII. The Crystal Structures of the 1 : 1 Adducts of Copper(I) Chloride, Bromide and Thiocyanate With Quinoline
Authors: Healy PC , Skelton BW , Waters AF , White AH
Published: September 2010

Adducts (1 : 1) of copper(I) chloride, bromide and thiocyanate with quinoline have been synthesized and have been the subject of single-crystal X-ray structure determinations at 295 K. Crystals of the chloride are orthorhombic, P 212121, a 15.358(7), b 14.309(6), c 3.801(2)Ǻ, Z 4; R was 0.055 for 541 'observed' reflections. Crystals of the bromide are monoclinic, C2/c, a 19.417(5), b 14.048(4), c 15.753(6) Ǻ, β 125.31(2)°, Z 4 tetramers; R was 0.049 for 1138 'observed' reflections. Crystals of the thiocyanate are monoclinic, P 21/c, a 5.682(1), b 10.412(2), c 16.838(5)Ǻ, β 97.48(2)°, Z 4 f.u .; R was 0.045 for 914 'observed' reflections. The chloride takes the form of the common 'stair' polymer, unexpectedly, while the thiocyanate is an expanded version of the same. The bromide provides a second example of a novel tetrameric 'basket' structure exemplified previously by the iodide analogue.
Lanthanide Ion Complexes of Calixarenes. VIII. Bimetallic Lanthanide Complexes of p-t-Butylcalix[8]arene From Dimethylformamide Solutions
Authors: Harrowfield JM , Ogden MI , White AH
Published: September 2010

Reaction of lanthanide(III) ion p- toluenesulfonates with a warm p-t- butylcalix [8] arene (L) solution in dmf/triethylamine ( dmf denotes N,N- dimethylformamide ), yields crystalline 2 : 1 Ln/ligand adducts, as dmf solvates: [Ln2(L-6H)( dmf )5]. xdmf , Ln = La, Pr, Lu and Eu (previously recorded; 2 phases) have been characterized by single-crystal X-ray studies; all phases are triclinic but only the praseodymium and α-form of the europium derivative are isostructural : Ln = La, Pr, α- Eu have Z = 2 formula units, while Ln = β- Eu , Lu have Z = 4. In all cases, the stoichiometry of the complex molecule is the same and the same as that of the dmso adducts recorded in the previous paper, with similar ligand dispositions.
Rearrangement Products From the Acetylation of Totaryl Methyl Ether
Authors: Bendall JG , Cambie RC , Metzler MR , Moratti SC , Rutledge PS , Woodgate PD
Published: September 2010

Treatment of totaryl methyl ether (1) with MeCOCl/TiCl4 gives three products of rearrangement in addition to the expected acetyl derivative (2). The structures of these by-products are discussed together with proposed mechanisms for their formation.
Cyclopentadienyl- and Cyclopentadienyl-osmium Chemistry. XXXVIII. Synthesis and X-Ray Structure of Ru(C6H4Me-p)(PPh3)2(η-C5H5).CH2Cl2
Authors: Adams CJ , Bruce MI , Coghlan DR , Skelton BW , White AH
Published: September 2010

The reaction between RuCl (PPh3)2(η-C5H5) and LiC6H4Me-p afforded Ru (C6H4Me-p)(PPh3)2(η-C5H5) (76%), structurally characterized by a single-crystal X-ray study at c. 295 K. Crystals are triclinic, Pī , a 16.607(4), b 11.397(3), c 11.076(5)Ǻ, α 94.90(3),β 99.52(3), γ 90.43(2)°, Z 2; R was 0.036 for 6246 'observed' diffractometer reflections. The p-tolyl moiety is σ-bonded to the ruthenium with an Ru-C bond length of 2.122(3)Ǻ. This value is compared with others found for Ru-C(spn) bonds (n=1-3) in σ-bond complexes; these range from 2.013(6) to 2.18Ǻ.
Reaction of Podocarpa-6,8,11,13-Tetraenes With m-Chloroperbenzoic Acid and With Dimethyldioxiran: Synthesis of Methyl 6-α,7-α-Epoxy-12-methoxy-podocarpa-8,11,13-trien-19-oate
Authors: Cambie RC , Grimsdale AC , Rutledge PS , Walker MF , Woodgate PD
Published: September 2010

The reaction of some podocarpa-6,8,11,13-tetraenes with m-chloroperbenzoic acid in either a one-phase system or a two-phase system with an aqueous buffer leads to epoxide-opened products. Successful epoxidations have been achieved in high yield by using the neutral oxidant dimethyldioxiran. The hydroboration -oxidation of methyl 12-benzyloxypodocarpa-6,8,11,13-tetraen-19-oate has been examined.
Some Transformations of 1,6,7,7-Tetrachlorobicyclo[4.1.0]heptan-3-one. Crystal and Molecular Structure of 4-(Dichloromethylene)-1-methyl-5,6-dihydro-1h-indazol-7(4H)-one
Authors: Sims CG , Skelton BW , Wege D , White AH
Published: September 2010

Treatment of the title tetrachloro ketone with triethylamine generates 6,7,7-trichlorobicyclo-[4.1.0]hept-1(2)-en-3-one (4), which can be trapped by furan to give two cycloadducts. In the absence of trapping agent, compound (4) undergoes a methylenecyclopropane rearrangement to yield 5-chloro-6-( dichloromethylene ) bicyclo [3.1.0]hexan-2-one. The strained enone (4) can also be intercepted by diazomethane, which affords the title indazolone, whose characterization was supported by a single-crystal X-ray study.
Constituents of Eupomatia Species. xiv. The Structures of Eupomatilone-1, -2, -3, -4, -5, -6 and -7 Isolated From Eupomatia Bennettii
Authors: Carroll AR , Taylor WC
Published: September 2010

On the basis of spectroscopic evidence, the eupomatilones (from eupomatilone-1 to -7) isolated from Eupomatia bennettii F. Muell. were shown to be degraded lignans . Eupomatilone-1 was assigned the structure (1), cis-4-methyl-3-methylene-5-(3″,4″,5″,6′-tetramethoxy-4′,5′-methylenedioxybiphenyl-2′-yl)dihydrofuran-2(3H)-one. The other six eupomatilones differ from eupomatilone-1 either in the degree of oxygenation of the biphenyl system or in the substitution of the furanone ring. Atropisomerism was observed with the compounds.
Arthur J. Birch
Authors: Rickards RW
Published: September 2010

No Abstract Available.
The Mechanism of the Mitsunobu Reaction. III. The Use of Tributylphosphine
Authors: Camp D , Jenkins ID
Published: September 2010

31P n.m.r . studies indicate that, when tributylphosphine is used in the Mitsunobu esterification reaction, clean formation of a single intermediate, an alkoxyphosphonium carboxylate, is apparent. In the absence of acid, at least two species are observed, a dialkoxytributylphoshorane and the corresponding alkoxyphosphonium salt. The order of mixing of the reagents can dramatically change the mechanism and stereochemistry of esterification reactions.
The Heat of Formation of Formaldimine
Authors: Smith BJ , Pople JA , Curtiss LA , Radom L
Published: September 2010

Ab initio molecular orbital theory at the G 2 level has been used to predict new values for the heat of formation of formaldimine (CH2=NH): ?Hfº0 = 94 ±10 kJ mol-1 and ?Hfº298 = 86 ±10 kJ mol-1.
Organolanthanoids. XVII. The Synthesis of Bis(diphenylphosphinocyclopentadienyl)ytterbium(II) and Derived Heterobimetallic Complexes [Yb(thf)n(C5H4PPh2)2Z] [Z=Ni(CO)2, Mo(CO)4 or PtMe2; n = 1 or 2; thf = Tetrahydrofuran]. The X-Ray Crystal-Structure of [Yb(thf)2(C5H4PPh2)2Ni(CO)2]
Authors: Deacon GB , Forsyth CM , Patalinghug WC , White AH , Dietrich A , Schumann H
Published: September 2010

Reaction of diphenylphosphinocyclopentadiene with Yb (C6F5)2 or with ytterbium metal and Hg(C6F5)2 in tetrahydrofuran ( thf ) gives, after workup with toluene, the phosphinoytter-bocene , [Yb (C5H4PPh2)2( thf )]. Treatment with thf or with N,N,N′,N′- tetramethylethane-1,2-diamine ( tmen ) yields [ Yb (C5H4PPh2)2L2] (L = thf or L2 = tmen ). Redox trans- metallation between ytterbium metal and Tl (C5H4PPh2) in l,2-dimethoxyethane ( dme ) gives thallium metal and [ Yb (C5H4PPh2)2(dme )]. The ytterbium-transition metal hetero-bimetallics [ Yb ( thf ) (C2H4PPh2)2Z]. nPhMe [Z = Ni(CO)2, Mo(CO)4 or PtMe2, n = 2/3 or 1] have been prepared by reaction of [ Yb ( thf )(C5H4PPh2)2] with Ni(CO)2(PPh3)2, Mo(CO)4( nbd ) ( nbd = norbornadiene ) or PtMe2(cod) (cod = cycloocta-1,5-diene) in toluene. Treatment of
the heterobimetallics with tetrahydrofuran [Z = PtMe2 or Mo(CO)4] or a preparation in thf /toluene [Z = Ni(CO)2] yields [ Yb ( thf )2(C5H4PPh2)2PtMe2]. thf, [ Yb ( thf )2(C2H4PPh2)2Mo(CO)4]. thf and [ Yb ( thf )2 (C5H4PPh2)2Ni(CO)2]. The X-ray crystal structure of the last compound (triclinic, space group Pi, a 14.514(5), b 13.565(1), c 10.866(5) 93.11(2), β 104.65(3), γ 97.25(2)�, U 2045 � 3 , Z 2, 5141 data refined to R 0.031) reveals eight-coordinate ytterbium with a pseudo-tetrahedral arrangement of two thf ligands and the cyclopentadienyl ring centroids of two ή5 -diphenylphosphinocyclopentadienide ligands . The latter are also bonded through phosphorus to the Ni(CO)2 group, resulting in tetrahedral stereochemistry for nickel. Infrared spectroscopy suggests the presence of ytterbium- isocarbonyl bonding in solid [ Yb ( thf )(C2H4PPh2)2Z] [Z = Ni(CO)2 or Mo(CO)4].