EPR- und Ligandenfeld-Spektren von Chlorovanadaten(IV). Die Kristallstruktur von PPh4[VxTi2–xCl9] (x = 0,15)

E.P.R. and Ligand Field Spectra of Chlorovanadates(IV). The Crystal Structure of PPh₄[V_xTi_2–xCl₉] (x = 0.15) Black, moisture-sensitive crystals of PPh₄[V_xTi_2–xCl₉] (x = 0.15) are formed by the reaction of titanium tetrachloride and PPh₄[VCl₅] in dichloromethane. Its EPR and ligand field spectra as well as those of PPh₄[VCl₅] and (PPh₄)₂[V₂Cl₉][VCl₅] · CH₂Cl₂ were recorded. In the mixed crystals of PPh₄[V_0.15Ti_1.85Cl₉], the existence of [VTiCl₉]^? ions consisting of trigonally distorted, face sharing octahedra can be proven by the spectra. The spectra of the compounds with [VCl₅]^? ions can only be explained when a significant Jahn-Teller distortion of the trigonal bipyramids is assumed; this distortion was not detected in the crystal structure determination of (PPh₄)₂[V₂Cl₉][VCl₅] · CH₂Cl₂. The crystal structure of PPh₄[V_0.15Ti_1.85Cl₉] was determined by X-ray diffraction (2588 independent observed reflexions, R = 0.044). Crystal data: triclinic, space group P1 , a = 1090.4, b = 1217.4, c = 1287.7 pm, α = 73.19°, β = 69.87°, γ = 82.15°, Z = 2. The compound consists of PPh₄^⊕ and [V_0.15Ti_1.85Cl₉]^? ions. In the anions, Ti and V atoms are distributed statistically in the two face sharing octahedra.     

[Li7(CHPMe2NSiMe3)3(OSiMe2nBu)]2, ein Gemischtligand-Li14-Cluster mit dem Carbdianion (CHPMe2NSiMe3)2−

[Li₇(CHPMe₂NSiMe₃)₃(OSiMe₂ⁿBu)]₂, a Mixed-Ligand-Li₁₄ Cluster with the Carbdianion (CHPMe₂NSiMe₃)^2? The title compound is formed as colourless moisture and oxygen sensitive crystals by the reaction of [LiCH₂PMe₂NSiMe₃]₄ with zinc or cobalt chloride in a toluene suspension in the presence of silicongrease (–OSiMe₂–)_n and n-butyllithium. It is characterized by multinucleus NMR spectroscopy and by crystal structure determinations of two different crystal individuals. 1. Space group P1 , Z = 1, lattice dimensions at ?70 °C: a = 1272.0, b = 1392.6, c = 1417.6 pm, α = 115.33°, β = 96.75°, σ = 106.81°; R = 0.042. 2. Space group P2₁/n, Z = 2, lattice dimensions at ?50 °C: a = 1424.8, b = 1457.1, c = 1997.0 pm, β = 90.32, R = 0.069.     

Die Kristallstruktur von [TeCl3(15-Krone-5)]SbCl6

The Crystal Structure of [TeCl₃(15-crown-5)]SbCl₆ The title compound is synthesized by the reaction of tellur tetrachloride, 15-crown-5 and antimony pentachloride in acetonitrile solution, forming colourless crystals, which were characterized by IR spectroscopy and an X-ray structure determination. Space group Pnma, Z = 4, 1966 observed unique reflections, R = 0.072, R_w = 0.052. The compound forms ions [TeCl₃(15-crown-5)]⁺ and SbCl₆^?; in the cation the tellurium atom is eightfold coordinated by the three chlorine atoms and the five oxygen atoms of the crownether molecule (Te? O bond lengths 266 and 279 pm).     

Totalsynthese von Betalainen

A total synthesis of betalaine pigments ( 6 ) is described. The key intermediate is betalamic acid in the form of its dimethyl ester semicarbazone ( 9 ), which was transformed with L-proline ( 16 ) into indicaxanthine dimenthl ester ( 5 ), with L-cyclodopa methul ester ( 17 ) into betanidine trimethyl ester ( 3 ) and by hydrolysis of the latter into betanidine ( 2 ).     

H-C-SiH3: direct generation and spectroscopic identification of ethylidene's cousin

Ground-state triplet silaethylidene, generated directly by the reaction of 3P carbon atoms with silane under matrix isolation conditions in solid Ar (10-12 K), has been thoroughly characterized by the EPR and IR spectra of both the parent and perdeuterated isotopologs. A theoretical anharmonic vibrational analysis based on a CCSD(T)/cc-pVTZ complete quartic force field gave remarkable agreement with the experimental IR fundamentals, generally within 10 cm-1 and without any empirical scaling of the ab initio frequencies. Silaethylidene exhibits a Cs minimum with a H-C-Si angle near 153 degrees , but the barrier to H-C-Si linearity (C3v symmetry) is only 0.24 kcal mol-1. This minuscule barrier can be surmounted by zero-point vibrations, as evident from the EPR data. The triplet stabilizing effect of the electropositive SiH3 group amounts to about 15 kcal mol-1.     

DPP dyes as ligands in transition-metal complexes

The DPP dyes (=diketopyrrolopyrrole) 1 are deprotonated to give the corresponding dianions 2. These are treated with two moles of the transition-metal complexes [L(n)MX]=[(Ph(3)P)(2)MX] (M=Cu, Ag; X=Cl, NO(3)), [(Ph(3)P)AuCl], [(Et(3)P)AuCl], [(tBuNC)AuCl], [(Ph(3)P)(2)PdCl(2)], and [(Ph(3)P)(2)PtCl(2)] to give the novel bismetalated DPP dyes [L(n)MN[C(3)R(1)(O)](2)NML(n)] (4-10). In comparison with the starting materials, these compounds show better solubilities, high fluorescence quantum yields (Phi > or = 80 %), and bathochromic absorptions. The compounds 4 c, 5 a, 6 b, 6 c, 6 e, 7 c, and 8 c were characterized by X-ray crystallography. The copper and silver atoms in 4 c and 5 a are trigonal planar and are surrounded by the P atoms of the phosphane ligands and the N atom of the DPP dianion 2. Both metals are somewhat forced out-of-plane, and the P(2)M plane and the phenyl planes of R1 are twisted by > or = 70 degrees and < or = 25 degrees, respectively, towards the chromophore plane. The gold atoms in 6-8 are linearly coordinated to one N and one P (6 b, c, e, 7 c) or one C atom (8 c), respectively. The gold atoms are only slightly pressed out-of-plane, and the P substituents are staggered so that there is enough space for the planarization of R(1) into the plane of the chromophore. Compound 8 c shows intermolecular d(10)-d(10) interactions between Au(I) centers of different molecules, and these interactions lead to infinite chains of parallel orientated molecules in a gauche conformation of neighbors (torsion angle=150 degrees) in the crystal.     

Acylation of a novel quinoxalinyl substituted pyrazole derivative. synthesis,quantum chemistry calculations,and x-ray structure analysis

The preparation of N-acetylpyrazolyl-quinoxalines and results of semiempirical MO calculations are presented. The structure determination of the isomers 3a, b was achieved by X-ray analysis.