Alternativ-Liganden. XXVI [1]. M(CO)4L-Komplexe (M  Cr,Mo, W) der Chelatliganden Me2ESiMe2(CH2)2E′Me2 (Me  CH3; E  P,As; E′  N,P, As)

Alternative Ligands. XXVI. M(CO)₄ L-Complexes (M ? Cr, Mo, W) of the Chelating Ligands Me₂ESiMe₂(CH₂)₂E′ Me₂ (Me ? CH₃; E ? P, As; E′ ? N, P, As) The reaction of M(CO)₄NBD (NBD = norbornadiene; M ? Cr, Mo, W) with the ligands Me₂ESiMe₂(CH₂)₂E′ Me₂ yields the chelate complexes (CO)₄M[Me₂ESiMe₂]) for E,E′ ? P, As, but not for E and /or E′ ? N. The NSi group is not suited for coordination because of strong (p-d)π-interaction. In the case of the ligands with E ? P or As and E′ ? N chelate complexes can be detected in the reaction mixture, but isolable products are complexes with two ligands coordinated via the E donor group. The new compounds are characterized by analytical and spectroscopic (IR, NMR, MS) investigations. The spectroscopic data are also used to deduce the coordinating properties of the ligands. X-ray diffraction studies of the molybdenum complexes (CO)₄Mo[Me₂ESiMe₂(CH₂)₂AsMe ₂] (E ? P, As) in accord with the observed coordination effects show only small differences between SiE and CE donor functions. Attempts to use the ligands Me₂ESiMe₂(CH₂)₂AsMe₂ (E ? P, As) for the preparation of Fe(CO)₃L complexes result in the fission of the SiE bonds and the formation of the binuclear systems Fe₂(CO)₆(EMe₂)₂ (E ? P, As) together with the disilane derivative [Me₂Si(CH₂)₂AsMe₂]₂.     

Perfluormethyl-Element-Liganden. XXXV. Reaktivität metallierter Phosphane und Arsane des Typs π-C5H5(CO)3MER2 (M  Cr,Mo, W; E  P,As; R  CF3, CN)

Perfluoromethyl-Element-Ligands. XXXV. Reactivity of Metallated Phosphanes and Arsanes of the Type π-C₅H₅(CO)₃MER₂ (M ? Cr, Mo, W; E ? P, As; R ? CF₃, CN) The influence of the complex fragments π-C₅H₅(CO)₃M (M ? Cr, Mo, W) on the basicity of the metallated phosphanes or arsanes π-C₅H₅(CO)₃MER₂ (E ? P, As; R ? CF₃, CN) has been investigated by reactions with sulfur, methyliodide, fluorotrichloromethane, and W(CO)₅THF, respectively. π-C₅H₅(CO)₃ME(CF₃)₂ (E ? P: 1a–c ; E ? As: 2a–c ) react with sulfur only for E ? P to give the complexes π-C₅H₅(CO)₃P(S)(CF₃)₂ ( 5a–c ) in good yield. The attempted thermal transformation of the phosphane sulfides to η² coordinated (CF₃)₂P?S complexes proves unsuccessful. The reactions of 1a–c, 2a–c and π-C₅H₅(CO)₃MP(CN)₂ ( 3a–c ) with CH₃I or CCl₃F do not lead to onium salts, but to cleavage of the M–E bonds forming π-C₅H₅(CO)₃MX (X ? I, Cl) and CH₃ER₂ and R₂ECCl₂F, respectively. The reactivity depends on ER₂ and M: P(CF₃)₂ > P(CN)₂ > As(CF₃)₂; Cr > Mo > W. Due to the low donor ability of the complexes 1a–c, 2a–c and 3a–c binuclear compounds π-C₅H₅(CO)₃MER₂W(CO)₅ (E ? As, R ? CF₃: 11a–c ; E ? P, R ? CN: 12a–c ; ER₂?P(CN)Ph: 13a, b ) are obtained only with the highly reactive W(CO)₅THF. In case of the (CF₃)₂P bridged derivatives spontaneous CO-elimination leads to the threemembered ring systems ( 10a–c ).     

Kristallstrukturuntersuchungen an Verbindungen des Typs A3(M,Nb)8O21 (A  Tl,Ba; M  Fe,Ni)

Crystal Structure Investigations of Compounds with the A₃(M, Nb)₈O₂₁-Type (A ? Tl, Ba; M ? Fe, Ni) Tl₃Fe_0,5Nb_7,5O₂₁ (A), a hitherto unknown phase of the A₃(M, Nb)₈O₂₁-type, and Ba₃Fe₂Nb₆O₂₁ (B), Ba₃Ni_1.33Nb_6,66O₂₁ (C) were prepared and investigated by single crystal X-ray technique. ((A): a = 9.145(1), c = 11.942(1) Å; (B): a = 9.118(2), c = 11.870(1) Å; (C) a = 9.173(3), c = 11.923(1) Å, space group D? P6₃/mcm, Z = 2). There is a statistic occupation of the M-positions by Nb⁵⁺ and Fe³⁺ or Nb⁵⁺ and Ni²⁺, respectively. An other compound Ba₃Fe₂Ta₆O₂₁ is partially ordered in respect to Ta⁵⁺ and Fe³⁺. Calculations of the Coulomb-part of lattice energy are discussed.     

Structures and isomerizations of carbenoids H2CCCLiX (X  F,Cl)

Novel structures of H₂C?C?CLiX (X ? F, Cl) were determined using HF/STO-3G gradient method. Both of the carbenoids have two equilibrium structures, askew and linear forms, at the level of calculation. In the case X?F, the former is more stable, but in the case X=Cl, the latter is more stable. The frontier MOs are given and analyzed.     

Studies on olefins. IX—proton NMR study of some CH2CR1R2 and CHR3CR1R2 alkenes

The proton NMR spectra of 2,3,4,4-tetramethyl-3-t-butylpent-1-ene rotarners have been completely assigned by low temperature NOE measurements. Chemical shifts and cis and trans allylic coupling constants are unambiguously determined. It is shown that other 2-substituted propenes can be assigned on the basis of the coupling constants, but not from the chemical shift data. In 1,2-disubstituited propenes, however, the transoid coupling constant falls in the range of the cisoid coupling constant values of the 2-substituted propenes. Coupling constants cannot, therefore, be used in the 1,2-disubstituted propene series as a criterion for determining structure.     

Syntheses, characterization, and dioxygen reactivities of Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives: a Cu(III)2O2 intermediate exhibiting higher C-H activation

Six Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives (R3CY, R = Et, iBu, and Bn), [Cu(MeCN)(Et3CY)]SbF6 (1), [Cu(MeCN)(iBu3CY)]SbF6 (2), [Cu(MeCN)(Bn3CY)]SbF6 (3), [Cu(CO)(Et3CY)]SbF6 (4), [Cu(CO)(iBu3CY)]SbF6 (5), and [Cu(CO)(Bn3CY)]SbF6 (6), were prepared to probe the ability of copper complexes to effectively catalyze oxygenation reactions. The complexes were characterized by elemental analysis, electrochemical and X-ray structure analyses, electronic absorption spectroscopy, IR spectroscopy, 1H NMR spectroscopy, and ESI mass spectrometry. The crystal structures of 1-3 and 6 and the CO stretching vibrations (nuCO) of 4-6 demonstrate that the ability of R3CY to donate electron density to the Cu(I) atom is stronger than that of the previously reported ligands, 1,4,7-triazacyclononane (R3TACN) and 1,4,7-triazacyclodecane (R3TACD). Reactions of complexes 1-3 with dioxygen in THF or CH2Cl2 at -105 to -80 degrees C yield bis(mu-oxo)dicopper(III) complexes 7-9 as intermediates as confirmed by electronic absorption spectroscopy and resonance Raman spectroscopy. The Cu-O stretching vibrations, nu(Cu-O) for 7 (16O2: 553, 581 cm-1and 18O2: 547 cm-1) and 8 (16O2: 571 cm-1 and 18O2: 544 cm-1), are observed in a lower energy region than previously reported for bis(micro-oxo) complexes. The decomposition rates of complexes 7-9 in THF at -90 degrees C are 2.78 x 10-4 for 7, 8.04 x 10-4 for 8, and 3.80 x 10-4 s-1 for 9. The decomposition rates of 7 and 8 in CH2Cl2 were 5.62 x 10-4 and 1.62 x 10-3 s-1, respectively, and the thermal stabilities of 7-9 in CH2Cl2 are lower than the values measured for the complexes in THF. The decomposition reactions obeyed first-order kinetics, and the H/D isotope experiments for 8 and 9 indicate that the N-dealkylation reaction is the rate-determining step in the decomposition processes. On the other hand, the decomposition reaction of 7 in THF results in the oxidation of THF (acting as an exogenous substrate) to give 2-hydroxy tetrahydrofuran and gamma-butyrolactone as oxidation products. Detailed investigation of the N-dealkylation reaction for 8 by kinetic experiments using N-H/D at -90 degrees C showed a kinetic isotope effect of 1.25, indicating that a weak electrostatic interaction between the N-H hydrogen and mu-oxo oxygen contributes to the major effect on the rate-determining step of N-dealkylation. X-ray crystal structures of the bis(micro-hydroxo)dicopper(II) complexes, [Cu2(OH)2(Et3CY)2](CF3SO3)2 (10), [Cu2(OH)2(iBu3CY)2](CF3SO3)2 (11), and [Cu2(OH)2(Bn3CY)2](ClO4)2 (12), which have independently been prepared as the final products of bis(micro-oxo)dicopper(III) intermediates, suggest that an effective interaction between N-H and mu-oxo in the Cu(III)2(micro-O)2 core may enhance the oxidation ability of the metal-oxo species.     

Zur Kenntnis komplexer Fluoride mit Cu2+ und Pd2+: MPtF6 (M  Pd,Cu) und RbCuPdF5

On Complex Fluorides with Cu²⁺ and Pd²⁺: MPtF₆ (M ? Pd, Cu) and RbCuPdF₅ For the first time single crystals of PdPtF₆ (green), trigonal-rhomboedric, a = 503.8, c = 1431.6 pm, spcgr. R3 ? C (No. 148), Z = 3, CuPtF₆ (orange), triclinic, a = 495.2, b = 498.5, c = 962.4 pm, α = 89.98, β = 104.23, γ = 120.35°, spcgr. P1 ? C (No. 2), Z = 2 and RbCuPdF₅ (orange brown, in connection with investigations on M^IPd₂F₅ [1]), orthorhombic, a = 626.9, b = 719.9, c = 1076.3 pm, spcgr. Pnma? D (No. 62), Z = 4, four circle diffractometer data, have been obtained.     

Alternativ-Liganden. III. Koordinatives verhalten von chelatliganden des typs me2XSi(Me2)CH2XMe2 (X  N und/oder P: Me  CH3)

Co-ordinative Properties of Chelating Ligands of the Type Me₂XSi(Me₂)CH₂XMe₂ (X ? N and/or P; Me ? CH₃) The reactions of the ligands L ? Me₂XSi(Me₂)CH₂XMe₂ (X ? N and/or P; Me ? CH₃) with M(CO)₆ and M(CO)₄norbor (norbor ? norbornadiene) (M ? Cr, Mo), respectively, yield derivatives of the types M(CO)₅L, M(CO)₄L, and M(CO)₄L₂, respectively. M(CO)₅L compounds are formed from the hexacarbonyls with Me₂NSiMe₂CH₂PMe₂, whereas the ligand Me₂NSiMe₂CH₂NMe₂ does not afford analogous derivatives under the same conditions. Even on substitution of the diene-ligand in M(CO)₄norbor by Me₂NSiMe₂CH₂PMe₂ the chelate complexes M(CO)₄NMe₂SiMe₂CH₂PMe₂ are not obtained, but the cis-disubstituted products M(CO)₄[PMe₂CH₂SiMe₂NMe₂]₂ with phosphorus acting as donor atom are produced. The ligands Me₂PSiMe₂CH₂XMe₂(X ? N, P) give the chelate complexes M(CO)₄PMe₂SiMe₂CH₂XMe₂ in high yields. The new compounds were identified by analytical and spectroscopic (PMR, IR, mass spectra) methods.     

The synthesis and structure of La5Pb3Z,Z  N,O. Interstitial derivatives of a Cr5B3-Type structure

Suitable proportions of La, La₄Pb₃ and La₂O₃ or LaN reacted in pressed pellets at 1050°–1250°C result in high yields of the title compounds. Single crystal X-ray studies of the oxide show it to be an isopointal, interstitial derivative of the Cr₅B₃ structure (I4/mcm, Z = 4, a = 8.6895(2) Å, c = 14.540(1) Å, R/R_w = 3.0/3.5%). Oxygen or nitrogen atoms are bound in (La2)₄ tetrahedra within chains along (0, 1 /2, z). Negligible dimerization of the type characteristic of Cr₅B₃ is indicated by the Pb2? Pb2 separation, 3.550(1) Å. The structure is compared with other related examples.     

Competitive Intramolecular Aryl‐ and Alkyl‐C?H Bond Activation and Ligand Evaporation from Gaseous Bisimino Complexes [Pt(L)(CH3)((CH3)2S)]+ (L=C6H5NC(CH3)?C(CH3)NC6H5)

Mechanistic details for the formation of methane from the title compound as well as the combined elimination of (CH₃)₂S/CH₄ are derived from various mass‐spectrometric experiments including deuterium‐labeling studies and DFT calculations. For the first process, i.e., methane formation, we have identified three competing pathways in which the intact, Pt‐bonded methyl group combines with a H‐atom that originates from a phenyl substituent (ca. 7%), the dimethyl sulfide ligand (ca. 41%), and a methyl group of the diazabutadiene backbone (ca. 52%). In contrast, in the combined (CH₃)₂S/CH₄ elimination, the methane is specifically formed from the Pt‐bound CH₃ group and a H‐atom provided by one of the phenyl groups (‘cyclometalation’).