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UV/VIS and ESR spectra of electron transfer reaction products in aprotic (cH⊕ < 0,1 ppm) solution can be measured in an especially designed and sealed glass apparatus and provide information on unknown facets of the microscopic pathway through the network of interdependent equilibria. For tetraphenyl-p-benzoquinone in tetrahydrofuran, single-electron reduction by a sodium metal mirror produces a red solution and, unexpectedly, after addition of 2.2.2. cryptand, contact with a potassium metal mirror generates a green (!) one. For both, ESR/ENDOR spectra prove the presence of tetraphenyl-p-benzoquinone radical anion. UV/VIS measurements provide the clue: In the equilibrium revealed by repetetive spectra recording, M·⊖solv + Me⊕solv ⇄ [M·⊖···Me⊖]solv, the radical anion is green (vm = 16900 cm-1) and the contact ion pair red (vm=18900 cm-1 ). On ion pair formation, therefore, the excitation energy of the radical anion increases by 0.25 eV.
The isobaric melting and boiling diagrams for the systems: trimethylchlorosilane/pyridine and trimethylchloromethane/pyridine are reproduced. Some measurements of the molar volume of mixtures between trimethylchlorosilane and pyridine and trimethylchloromethane and pyridine are reported. For both systems the molar excess volume has been calculated as a function of the mole fractions
The isobaric melting and boiling diagrams for the systems: dimethyldichlorosilane/pyridine and 2,2-dichloropropane/pyridine are reproduced. The existence of the incongruently melting addition compounds (CH3)2SiCl2 · (Pyridine)2 and [(CH3)2CCl2]3 · Pyridine could be proved. Some measurements of the molar volume of mixtures of pyridine and dimethyldichlorosilane, and pyridine and 2,2-dichloropropane are reported. For both systems the molar excess volume has been calculated as a function of the mole fractions.
The isobaric melting and boiling diagrams for the systems: pyridine/methyltrichlorosilane and pyridine/1,1,1-trichloroethane are reproduced. The existence of the congruently melting addition compound CH3SiCl3· (Pyridin)2 could be confirmed. Some measurements of the molar volume of mixtures between pyridine and methyltrichlorosilane and pyridine and 1,1,1-trichloroethane, respectively, are reported. For both systems the molar excess volume and for the system pyridine/methyltrichlorosilane the molar excess enthalpie have been calculated as a function of the mole fractions.
By analyzing the phase diagrams of some trimethylhalogenosilane/pyridine- and methyl-trichlorosilane/lutidine-systems the existence of the incongruently melting addition compounds Me3SiF · (Pyridine)2, Me3SiCl · (Pyridine)2, MeSiCl3, · (2.5-Lutidine)2, MeSiCl3, · (2.6-Lutidine)2, (MeSiCl3)2 · 3.5-Lutidine, and the congruently melting compounds MeSiCl3 · 2.4-Lutidine, MeSiCl3 · (3.5-Lutidine)2 was proven.
By analyzing the DSC heating curves and the resulting phase diagrams of the systems of dibromodimethylsilane and 2-, 3- or 4-methylpyridine the existence of the congruently melting addition compounds ((CH3)2SiBr2)2 · (3-methylpyridine) and (CH3)2SiBr2 · (4-methylpyridine)2, and the incongruently melting addition compounds ((CH3)2SiBr2)2 · (2-methylpyridine) and ((CH3)2SiBr2)2 · (4-methylpyridine) could be proved.
Phase equilibrium studies of the Lewis acid-base systems AlCl3/PyHBr and AlBr3/PyHI indicate the existence of congruently melting compounds of the molar ratios 1:1 and 2:3.
These results are quite different from those of our studies of the AlCl3/PyHCl and the AlBr3/PyHBr systems, in which four compounds in the molar ratios 1:1, 1:2, 1:3, and 2:3 could be detected.
The melting point of pyridinium iodide observed at 284,8 °C (decomp.) differs from the previously reported one.
Trimethylbromosilane and 3,4-lutidine form a 1:1 compound which is stable at room temperature. Single crystals of this compound can be isolated by sublimation. It crystallizes in the orthorhombic space group P 2121,21, with lattice constants a = 737,08(9) pm, b = 1295,7(1) pm, c = 1318,8(3) pm. The crystal structure was refined to Rw = 0,042 and proves an ionic structure.
The title compound has been prepared by the reaction of N-trimethylsilyl-iminotriphenylphos-phorane with copper(II) chloride in boiling CCl4 /C2H5OH, and forms moisture sensitive crystals, which are green in transmittance and black in reflexion. [Me3SiNPPh3 · CuCl2 ] 2 was characterized by its IR spectrum as well as by a crystal structure determination (4197 observed, independent reflexions, R = 0.049). The lattice dimensions are at 20 °C: a = 1102.7. b = 1407.3. c = 1560.2 pm; β = 94.27°; space group P21/n with two formula units in the unit cell. The complex consists of centrosymmetric, dimeric molecules with a planar Cu2 Cl2 ring (Cu-CI bond lengths 229 and 231 pm). A terminally bonded CI atom (Cu-CI = 221 pm) and the N atom of the Me3SiNPPh3 ligand (Cu-N = 198.5 pm) complete the coordination number four of the nearly planar surroundings of the Cu atoms.
[MONCl3 · NC - C2Cl3]2 has been prepared by the reaction of MONCl3 with trichloromethyl isocyanidedichloride, CCl3NCCl2 , in CH2Cl2 suspension. The compound forms redbrown. mois-ture sensitive crystals, which were characterized by their IR spectrum as well as by a crystal structure determination (2482 independent observed reflexions, R = 0.048). Crystal data (-70 °C): Space group P21/c, Z = 2, a = 674.2(2); b = 2128.2(11); c = 786.0(4) pm: β = 102.81(3)°. [MONCl3 • NC-C2Cl3]2 forms centrosymmetric dimeric molecules via chloro bridges with Mo-Cl bond lengths of 240.7 and 276.0 pm. The longer MoCl bond of the MOCl2MO ring is caused by the trans influence of the nitride ligand; the MoN bond length of 167 pm corresponds with a triple bond. The 2,3,3-trichloroacrylnitrile ligand is bonded by its nitrogen atom with a bond length of Mo -N = 216 pm; the Mo-N≡C-C sequence is almost linear with a remarkable short C-C bond of 143.0 pm.