摘要:

Crystals of [dimethyl(1-pyrazolyl)(2-pyridylmethoxy)gallato-N2,O,N3](η3-allyl)dicarbonylmolybdenum(II) are triclinic,a = 9.632(2),b = 9.798(2),c = 10.255(2) Å, α = 80.16(1), β = 87.38(1), γ = 81.75(1)°,Z = 2, space group. The structure was solved by conventional heavy-atom methods and was refined by full-matrix least-squares procedures toR = 0.033 andRw = 0.037 for 3000 reflections withI ≥ 3σ(I). The molecule has pseudo-octahedral coordination geometry with the tridentate [Me2Ga(N2C3H3)(OCH2(C5H4N))]−ligandfaciallycoordinated and the η3-allyl ligand occupying one coordination sitetransto the pyridyl nitrogen atom. Important bond lengths are Mo—O = 2.219(2), Mo—N(py) = 2.212(3), Mo—N(pz) = 2.232(2), Mo—C(allyl) = 2.290(4), 2.189(4), 2.341(4), Mo—CO (transto O) = 1.928(4), and Mo—CO (transto N) = 1.952(4) Å.

ISSN:0008-4042    

DOI:10.1139/v88-061

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Theabsorption spectra of BrClCS and Br2CS have been photographed under low resolution at room temperature. The electronic origins of BrClCS and Br2CS have been placed at 17116 and 16859 cm−1, respectively. Vibronic analyses show that the molecules are non-planar in their ā states. By fitting quadratic–Gaussian and quadratic–quartic double-minimum potentials to the observed vibrational levels of the out-of-plane manifolds, the equilibrium out-of-plane angles and the barrier heights to molecular inversion have been estimated to be 25 ± 1 deg and 541 ± 10 cm−1for BrClCS, and 17.5 ± 1 deg and 524 ± 10 cm−1for Br2CS. In the case of BrClCS, all six ā state vibrational frequencies have been obtained. In the case of Br2CS, only modes 1 (C—S stretch), 2 (symmetric C—Br stretch), 3 (in-plane Br—C—Br scissor), and 4 (out-of-plane bend) are active in the spectrum. Comparisons with other tetraatomic thiocarbonyls support the given assignment

ISSN:0008-4042    

DOI:10.1139/v88-062

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Densities and viscosities were determined for the 2-propanol + methylacetate + dichloromethane system at 298.15 K. From the experimental results, molar excess volumes and excess viscosities were calculated. Different expressions exist in the literature to predict these excess properties from the binary mixtures. The empirical correlation of Tsao–Smith and Toop is the best for this system.

ISSN:0008-4042    

DOI:10.1139/v88-063

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The temperature dependance of adiabatic compressibility minimum (TACM), sound velocity maximum (TSVM), and specific acoustic impedance (TSAIM) of water–cyclohexanone mixture has been studied by experimentally determining the sound velocity in and density of aqueous solution at different concentrations over a temperature range 36–77 °C. The structural contribution to the shift in TACM, TSVM, and TSAIM has been evaluated. The shifts are negative and increase with concentration. The results indicate that cyclohexanone behaves as a structure breaker at higher temperature.

ISSN:0008-4042    

DOI:10.1139/v88-064

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The disproportionation/combination ratio in the reaction between two 3,5-di-tert-butylcumyl radicals, generated by thermolysis of the corresponding diazene, is 0.21 ± 0.03 at 60 °C in benzene. This is much larger than the value of 0.06 found for the unsubstituted cumyl radicals. It is suggested that thetert-butyl groups hinder the formation of a parallel association complex, which has been proposed to account for the much smaller amount of disproportionation in the reaction between benzylic radicals as compared with alkyl radicals.

ISSN:0008-4042    

DOI:10.1139/v88-065

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The preparation of the title compounds demonstrates the bis-N-alkylation of secondary amines by formaldehyde, these labile ammonium inner salts being captured as diphenylboron chelates. Crystals of 5,5-trimethylene-2,2-diphenyl-1,3-dioxa-5-azonia-2-boratacyclohexane are orthorhombic,a = 8.8461(3),b = 10.7290(4),c = 15.8773(5) Å,Z = 4, space groupP212121, and those of 5,5-dimethyl-2,2-diphenyl-1,3-dioxa-5-azonia-2-boratacyclohexane monohydrate are monoclinic,a = 6.2432(3),b = 17.1469(8),c = 14.3701(5) Å, β = 90.647(3)°,Z = 4, space groupP21/n. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures toR = 0.030 and 0.047 for 1400 and 2258 reflections withI ≥ 3σ(I), respectively. Both compounds have aB,N-betaine structure, the six-membered chelate rings adopting chair conformations. Libration-corrected bond lengths, O—B = 1.508(3)−1.522(3) and C—B = 1.612(4)−1.637(4) Å, indicate relatively strong binding of the diphenylboron moiety to the oxygen atoms of theO,O-chelating ligands.

ISSN:0008-4042    

DOI:10.1139/v88-066

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Fumaratotriazoline (1) and amidotriazoline (3) undergo thermal first-order transformations in solution at 65 °C. The former affords the isomeric pyrrole5and its hydrolysis product6. A mechanism involving opening of the initial five-membered ring to form8, followed by closure to a new five-membered ring (9), is proposed. Amidotriazoline (3) loses N2on heating to form19. The experimental results are best accommodated in terms of a novel mechanism involving an electrocyclic ring closure, a [3 + 2] cycloreversion to form an ylide, a sigmatropic rearrangement of the ylide, and, finally, an electrocyclic ring-opening reaction.

ISSN:0008-4042    

DOI:10.1139/v88-067

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Lithiated carbanionic chelates α to P(O) groups are formed from four title compounds. Their infrared and13C and31P nuclear magnetic resonance spectra show that chelation induces peculiar structural perturbations that depend upon the nature of Y. The corresponding neutral precursors1–4are able to form bidentate coordinates with the Li cation, which can be observed in THF when Y = OMe or NMe2but in benzene only when Y = Me. They are probably intermediates in the lithiated base deprotonation of neutral compounds1–4.

ISSN:0008-4042    

DOI:10.1139/v88-068

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Molybdenum-95 nmr spectral data are reported for 40cis- andtrans-Mo(CO)4LL′ compounds and the chemical shifts discussed in relation to a simplified Ramsey expression for the paramagnetic shielding term. The identification of mixtures of products of the type Mo(CO)6−nLnis shown to be easily accomplished by95Mo nmr spectroscopy. The95Mo chemical shifts provide a sensitive probe of structural and electronic effects, as illustrated for several cyclic nitrogen ligands as well as a range of phosphine ligands in the Mo(CO)4LL′ complexes.

ISSN:0008-4042    

DOI:10.1139/v88-069

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is a suitable reagent for the spectrophotometric determination of uranium but results are easily influenced by the reaction conditions as well as various common ions and masking agents. Optimum conditions, which must be carefully maintained, are 30% (v/v) dimethylformamide, 0.1% triton X-100, ≥ 8 × 10−5 M5-Br-PADAP, 8 × 10−2 Mtriethanolamine, 7 × 10−3 Msodium fluoride, 10−2 M5-sulphosalicylic acid, and 579 nm. Sodium sulphate (10−2 M) and CDTA (5.7 × 10−3 M) may serve as additional masking agents. A previous separation of uranium by extraction with 0.1 Mtri-n-octylamine in benzene from 4 MHCl and re-extraction of 0.3 MHCl is recommended for analysis of natural water samples.

ISSN:0008-4042    

DOI:10.1139/v88-070

出版商:NRC Research Press    

年代:1988

数据来源: NRC