摘要:

The synthesis of a number of six-coordinate manganese, molybdenum, and tungsten carbonyl compounds incorporating both the bidentate bispyrazolyl gallate ligand, [Me2Ga(N2C3H3)2]−, and a neutral pyrazole ligand in a facial coordination arrangement are described. Variable temperature1H nmr studies have revealed interestingly different behaviours in solution for the valence isoelectronic species [Me2Ga(N2C3H3)2](N2C3H4)Mn(CO)3and [Me2Ga(N2C3H3)2](N2C3H4)Mo(CO)3−. X-ray structural analyses of crystalline samples of the two compounds have been carried out in an effort to shed light on these behavioural differences. Crystals of [Me2Ga(N2C3H3)2](N2C3H4)Mn(CO)3are monoclinic,a = 31.053(2),b = 8.0503(4),c = 15.8629(8) Å, β = 108.164(2)°,Z = 8, space groupC2/cand crystals of [(C2H5)4N]+{[Me2Ga(N2C3H3)2](N2C3H4)Mo(CO)3}−are monoclinic,a = 10.058(1),b = 20.6488(5),c = 13.533(1) Å, β = 93.800(5)°,Z = 4, space groupP21/n. Both structures were solved by Patterson and Fourier syntheses and were refined by full-matrix least-squares procedures to finalRvalues of 0.028 and 0.023 for 2613 and 4388 observed reflections for the Mn and Mo complexes, respectively. The neutral Mn complex and the complex Mo anion both have approximate mirror symmetry and both metal atoms have trigonally distorted octahedral coordination geometry. Important bond distances (corrected for thermal vibration) are: Mn—N, 2.074(3)–2.086(3), Mn—C, 1.795(4)–1.809(5), Mo—N, 2.291(2)–2.295(2), and Mo—C, 1.918(3)–1.936(3) Å. Although structural differences between these two species do offer plausible explanations for the differences observed in solution, it appears that other factors are more important.

ISSN:0008-4042    

DOI:10.1139/v81-456

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The products of photodimerization ofN-benzoylazacyclohex-2-ene-4-one (1) have been investigated by X-ray crystallography. Irradiation of a benzene solution of compound1leads to a mixture of head-to-head and head-to-tail,cis,anti,cisadducts, namely,cis,anti,cis-N,N′-dibenzoyl-3,12-diazatricyclo[6.4.0.02,7]dodecan-6,12-dione andcis,anti,cis-N,N′-dibenzoyl-3,9-diazatricyclo[6.4.0.02,7]dodecan-6,9-dione, compounds2and3respectively.

ISSN:0008-4042    

DOI:10.1139/v81-457

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Autoionization constants (Ks) of aqueous mixtures of tetrahydrofuran (THF) and 1,2-dimethoxyethane (DME) containing 10, 30, and 50 wt.% cosolvent in each case have been determined from emf measurements of the cell: Pt, H2(g, 1 atm)|KOH (m1), KBr (m2), solvent|AgBr, Ag at seven equidistant temperatures ranging from 5 to 35 °C. The standard free energies (ΔG0), entropies (ΔS0), and enthalpies (ΔH0) of autoionization of the solvents were also evaluated from these data. Relative free energy data, δΔG0(≡sΔG0 − wΔG0), for these solvents as well as those for dioxane (D) – water mixtures taken from the literature, when coupled with the previously determined transfer free energies of H+, ΔGt0(H+), yielded ΔGt0(OH−)app(≡ΔGt0(OH−) − ΔGt0(H2O)) values in the mixed solvents. Relative magnitudes of ΔGt0(H+) and ΔGt0(OH−)appand their non-Born parts, ΔGt,ch0(H+) and ΔGt,ch0(OH−)appin particular, suggest that the "basicity" of these aqueous cosolvents decreases in the order DME > THF > D and their "acidity" in the reverse order, as expected from structural and electronic consideration of these cosolvent molecules. Analysis of the relative entropie contributions,Tδ (ΔS0) (≡T(sΔS0 − wΔS0), for the autoionization of these aqueous cosolvents and in particular ΔSt0(H2O) values derived there from, suggests that while THF promotes three dimenstional (3D) ice-like water structures at initial compositions and D induces breakdown of the 3D structures right from the beginning, DME breaks down water structures at initial compositions, but induces some order around 4–14 mol% DME by forming the possible H-bonded bidentate DME–water complexes. And beyond certain compositions, depending upon the relative size and shape, all the cosolvents break down water structure due to packing imbalance.

ISSN:0008-4042    

DOI:10.1139/v81-458

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Standard free energies (ΔGt0) and entropies (ΔSt0) of transfer of hydrogen iodide from water to some aqueous solutions of tetrahydrofuran (THF), dioxane (D), and 1,2-dimethoxyethane (DME) have been determined by measuring the emf's of the cell: Pt, H2(g, 1 atm)|KOH (m1), KI (m2), solvent|AgI, Ag at seven equidistant temperatures ranging from 5 to 35 °C. In each of these ethereal solvent systems ΔGt0values of HI, as well as of HCl and HBr obtained from the literature, and particularly of the individual ions, suggest that while H+is increasingly stabilized, halide ions are increasingly destabilized due to the influence of cosolvent-induced larger "basicity" and smaller "acidity" of the mixed solvents compared to that of water, and both conformed to the expected order: D < THF < DME. Moreover, the relative order: Cl− > Br− > I−in all the solvent systems is ascribable to the combined effects of "acid–base" and "soft–soft" interactions and the superimposed quadrupolar interactions in the case of D and the charge transfer to solvent (CTTS) complexation effect, especially on I−in the case of THF. Analysis of the entropie contributions,TΔSt0, and particularly of the relative order of ΔY(≡TΔSt0(H+) + TΔSt,ch0(X−)) for X = Cl, Br, and I, in the light of the semi-quantitative theory proposed earlier by Kunduet al., reveals that at initial compositions, while THF promotes 3D structures of water, both D and DME break down the same; at higher compositions all the cosolvents disrupt the structure as usual due to packing imbalance. The nature and relative positions of ΔY–composition profiles also suggest that while increase of hydrophobic groups of the cosolvents increases the stabilization, increase in hydrophilicity or H-bonding sites decreases the stabilization of the 3D structure of water.

ISSN:0008-4042    

DOI:10.1139/v81-459

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Tetrasulphur tetranitride is oxidized quantitatively at room temperature to tetrathiazyl di(fluorosulphate) S4N4(SO4F)2. Conductance measurements in HSO3F show this compound to dissociate into ions. The vibrational spectra of the cation are uniquely consistent with a flexible planar structure ofD4hsymmetry, and the anion bands are characteristic of ionic SO3F−. CNDO and EHMO calculations indicate that the planar form of the cation is stable but easily deformable.

ISSN:0008-4042    

DOI:10.1139/v81-460

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

not available

ISSN:0008-4042    

DOI:10.1139/v81-461

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Thujone1was degraded to the thujaketonic acids5and18which were used as starting materials for the synthesis of pyrethroid analogs8,12–17,21–24, and27–35.

ISSN:0008-4042    

DOI:10.1139/v81-462

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The results of a uv–visible spectroscopic study of the interaction of 1,3-dinitrobenzene (DNB) with hydroxide ion in aqueous dimethylformamide (DMF) media are reported. Formation of several spectral species has been discerned, depending on factors such as the relative concentrations of the reactants, the time scale of the experiments, and the medium composition. The principal interaction is formation of the 1-hydroxy-2,4-dinitrocyclohexadienate anion. The molar absorptivities of this σ-complex, and the equilibrium constants (Ke) for its formation, have been determined as a function of medium composition. Values ofKeincrease from 7.5 M−1to 3 × 105M−1as the DMF content of the medium is changed from 57.4 to 95.8 mol% DMF. A solvent isotope effect,Ke(D2O)/Ke(H2O), of ca. 0.4 has been observed. Structural and medium effects in this and related systems are evaluated. Correlations between logKeandH−are examined using the stoichiometric as well as the calculated free hydroxide ion concentrations. Attention is drawn to an important condition for equilibrium constant measurement in systems where one of the interacting species contributes significantly to the overall basicity, or to another property of the medium.

ISSN:0008-4042    

DOI:10.1139/v81-463

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Kinetic data have been evaluated for hydrogen exchange in 1,3-dinitrobenzene (DNB), occurring at the 2-position, in dimethylformamide (DMF) – D2O mixtures containing deuteroxide ion. The pseudo first order rate constants for exchange,kobs, show inverse dependence on the initial DNB concentration, which can be quantitatively related to the extent of σ-complex formation in these systems. The profile forkobsas function of medium composition exhibits a maximum at ca. 70 mol% DMF, and ϵappfor σ-complex formation reaches a plateau at about the same medium composition. The equilibrium constants for σ-complex formation,Ke, are used to calculate the free, or uncomplexed, deuteroxide ion concentrations, which then allow one to calculatek2, the second order rate constants for exchange. Thek2values show a uniformly increasing tendency with increased DMF content. Correlations with medium basicity are examined, and the nature of the logk2and logKevs.H−plots afford insight into the origin of the medium dependence of proton exchange. The results of the present study are consistent with the σ-complex being an unreactive form of the substrate towards exchange, which occurs via uncomplexed DNB present in small concentration. The study also rules out the possibility that the colored species present in these systems is the carbanion formed on deprotonation of DNB.

ISSN:0008-4042    

DOI:10.1139/v81-464

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Ozonolysis oftrans-2,3-dichloro-2-butene (5a), oftrans-3,4-dichloro-3-hexene (5b), and of 1,2-dichlorocyclohexene in methanol and in solutions of sodium methoxide in methanol have been examined. They afforded in high yields the corresponding ester fragments methyl acetate (6a), methyl propionate (6b), and dimethyl adipate (8), respectively. By trapping with phenylacetylene and formation of 1,1-dichloro-2,2-dimethoxy-2-phenylethane, the presence of methyl hypochlorite in the ozonolysis products was established. A reaction course has been proposed which is in accord with these results.

ISSN:0008-4042    

DOI:10.1139/v81-465

出版商:NRC Research Press    

年代:1981

数据来源: NRC