Infrared and Raman spectra were recorded for the trans,trans (EE), cis,cis (ZZ), and cis,trans (ZE) isomers of 1,4-difluorobutadiene (DFBD). From these spectra and frequencies predicted from the adiabatic connection method, which is a hybrid of Hartree−Fock and density−functional theories, complete assignments of fundamentals were made for the observable s-trans configurations. The fundamentals for the trans,trans isomer are (in cm-1):  (ag) 3091, 3048, 1681, 1325, 1280, 1151, 1121, 409, 383; (au) 934, 798, 227, 154; (bg) 897, 830, 397; and (bu) 3086, 3056, 1638, 1299, 1221, 1088, 621, 133. The fundamentals for the cis,cis isomer are (in cm-1):  (ag) 3118, 3088, 1676, 1410, 1248, 1134, 946, 751, 232; (au) 914, 762, 330, 78; (bg) 897, 789, 580; and (bu) 3109, 3092, 1624, 1340, 1215, 1044, 632, 165. The fundamentals for the cis,trans isomer are (in cm-1):  (a‘) 3114, 3082, 3062, 3036, 1690, 1629, 1391, 1313, 1253, 1224, 1138, 1129, 1008, 706, 504, 308, 138; and (a‘ ‘) 929, 887, 824, 758, 526 (calculated), 230, 155. Overall agreement between the assignments and the predicted frequencies is quite good. With allowance for the difference between modes strongly dependent on CF or CCl motions, a very good correlation was found between the fundamentals of the three isomers of DFBD and the corresponding isomers of 1,4-dichlorobutadiene. Both sets of isomers are of special interest because they exhibit the cis effect, in which the cis,cis isomer has the lowest energy and the trans,trans isomer has the highest energy.

Microwave spectra in the 5.5−17.5-GHz region have been observed for cis,trans-1,4-difluorobutadiene, for its 13C isotopomers in natural abundance, for the four singly substituted deuterium isotopomers, and for the 1,4-d 2 species. For the parent species fitting 37 lines to a Watson-type Hamiltonian with the five quartic centrifugal distortion constants gave A = 12 988.333(1), B = 1467.8791(3), and C = 1318.5845(3) MHz. Stark effect measurements on three transitions of the parent species gave a dipole moment of 2.309(5) D with components μ a = 0.660(4) D and μ b = 2.213(5) D. Surprisingly, the B rotational constant for the 2-d 1 isotopomer, as indexed from the trans end, is larger than that for the normal species, and the rotational constants for the 3-d 1 isotopomer are also anomalous. Nonetheless, a complete, 17-parameter structure is proposed for this planar molecule and compared with density functional theory predictions made with the adiabatic connection method. Structural parameters are also compared with those of butadiene itself.

Reactions of carboxylic acids with lead play an important role in the atmospheric corrosion of lead and lead-tin alloys. This is of particular concern for the preservation of lead-based cultural objects, including historic lead-tin alloy organ pipes. Two initial corrosion products, Pb(3)O(2)(CH(3)COO)(2)·0.5H(2)O (1) and Pb(2)O(HCOO)(2) (2), had been identified through powder diffraction fingerprints in the Powder Diffraction File, but their structures had never been determined. We have crystallized both compounds using hydrothermal solution conditions, and structures were determined using laboratory and synchrotron single-crystal X-ray diffraction data. Compound 1 crystallizes in P1, and 2 in Cccm. These compounds may be viewed as inorganic-organic networks containing single and double chains of edge-sharing Pb(4)O tetrahedra and have structural similarities to inorganic basic lead compounds. Bond valence sum analysis has been applied to the hemidirected lead coordination environments in each compound. Atmospheric exposure experiments contribute to understanding of the potential for conversion of these short-term corrosion products to hydrocerussite, Pb(3)(CO(3))(2)(OH)(2), previously identified as a long-term corrosion product on lead-rich objects. Each compound was also characterized by elemental analysis, thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), and Raman spectroscopy.

The 13 C 2 and d 2 isotopomers of 1,1,2,2-tetrafluoroethane (TFEA) have been synthesized. Raman spectra of these new species have been recorded, and infrared spectra of all three isotopomers, including some regions with high-resolution at -100°C, have also been recorded. Guided by recently published calculations of frequencies and infrared intensities and the new spectra, we have revised the previous assignments of fundamentals for the two rotamers of the normal species of TFEA. Assignments of the fundamentals for both rotamers of the 13 C 2 and d 2 isotopomers are proposed. The anti rotamer is the more abundant species in the gas phase and, to a lesser extent, in the liquid phase and the only species in the crystal phase. Thus, the assignments of the anti rotamer of all three isotopic species are complete and supported by isotope product rules, but the assignments for the gauche rotamers are incomplete. Estimates of the missing frequencies for the gauche rotamer of the normal species are supplied.

Octahedral molybdenum chalcogenide clusters are the building blocks of the well-known Chevrel phases. Although the synthesis of molecular Mo 6 S 8 L 6 (L = PEt 3 and pyridine) clusters has been previously reported, a high yield and larger scale synthetic procedure is needed to produce soluble Mo 6 S 8 L 6 (L = Lewis base ligand) clusters, so that they can be used as precursors for the construction of novel network structures. Using the previously developed W 6 S 8 (4tert-butylpyridine) 6 synthesis as a starting point, a facile, high yield (70%) synthesis of Mo 6 S 8 (4-tert-butylpyridine) 6 from (Bu 4 N) 2 Mo 6 Cl 8 Cl 6 was developed. This general sulfidation reaction scheme can be extended to the direct preparation of many M 6 S 8 L 6 (M = W, Mo; L = Lewis base ligand) complexes. Three Mo 6 S 8 L 6 complexes (L = PEt 3 , methylamine, 4,4Ј-bipyridine) were also prepared via ligand exchange reactions with Mo 6 S 8 (4-tert-butylpyridine) 6 . The above Mo 6 S 8 L 6 complexes were characterized and their reactivity was compared with their tungsten counterparts. Crystal structures were found for Mo 6 S 8 (4-tert-butylpyridine) 6 , Mo 6 S 8 (4,4Ј-bipyridine) 6 , and Mo 6 S 8 (methylamine) 6 .