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ABSTRACT: Synthetic routes leading to two series of (eta(8)-cyclooctatetraenyl)lanthanide(III) scorpionate "mixed sandwich" complexes are reported. The early lanthanide derivatives (COT)Ln(Tp) (Ln = Ce (1), Pr (2), Nd (3), Sm (4)) and (COT)Ln(Tp(Me2)) (Ln = Ce (5), Pr (6), Nd (7), Sm (8)) (COT = eta(8)-cyclooctatetraenyl, Tp = hydrotris(pyrazolyl)borate, Tp(Me2) = hydrotris(3,5-dimethylpyrazolyl)borate) were obtained by reacting the dimeric halide precursors [(COT)Ln(mu-Cl)(THF)]2 with K[Tp] or K[Tp(Me2)], respectively For the late lanthanide elements a different synthetic route was developed. The complexes (COT)Ln(Tp) (Ln = Er (9), Lu (10)) were made by the reaction of (Tp)LnCl2(THF)1.5 with equivalent amounts of K2C8H8. All new compounds were isolated as intensely colored crystalline materials and fully characterized by elemental analyses and spectroscopic methods. The molecular structures of 4, 5, and 8 were elucidated by X-ray diffraction. The optical spectra of compounds 2 and 4-8 were run at room and low temperatures. From the spectra obtained, the underlying crystal field splitting patterns of complexes 2, 4, 6, and 7 were derived and simulated by fitting the free parameters of a phenomenological Hamiltonian. The parameters used allow the estimation of the crystal field strengths experienced by the Ln3+ central ions and the insertion of complexes 2, 4, 6, and 7 into empiric nephelauxetic and relativistic nephelauxetic series. Besides, the experimentally oriented non-relativistic and relativistic molecular orbital schemes of compound 6 were set up and compared with the results of previous model calculations on [Ln(COT)2]-, Pa(COT)2, and U(COT)2.
Inorganic Chemistry 01/2009; 48(2):760-72. · 4.60 Impact Factor
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ABSTRACT: Synthetic routes leading to two series of (η8-cyclooctatetraenyl)lanthanide(III) scorpionate “mixed sandwich” complexes are reported. The early lanthanide derivatives (COT)Ln(Tp) (Ln = Ce (1), Pr (2), Nd (3), Sm (4)) and (COT)Ln(TpMe2) (Ln = Ce (5), Pr (6), Nd (7), Sm (8)) (COT = η8-cyclooctatetraenyl, Tp = hydrotris(pyrazolyl)borate, TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate) were obtained by reacting the dimeric halide precursors [(COT)Ln(μ-Cl)(THF)]2 with K[Tp] or K[TpMe2], respectively For the late lanthanide elements a different synthetic route was developed. The complexes (COT)Ln(Tp) (Ln = Er (9), Lu (10)) were made by the reaction of (Tp)LnCl2(THF)1.5 with equivalent amounts of K2C8H8. All new compounds were isolated as intensely colored crystalline materials and fully characterized by elemental analyses and spectroscopic methods. The molecular structures of 4, 5, and 8 were elucidated by X-ray diffraction. The optical spectra of compounds 2 and 4−8 were run at room and low temperatures. From the spectra obtained, the underlying crystal field splitting patterns of complexes 2, 4, 6, and 7 were derived and simulated by fitting the free parameters of a phenomenological Hamiltonian. The parameters used allow the estimation of the crystal field strengths experienced by the Ln3+ central ions and the insertion of complexes 2, 4, 6, and 7 into empiric nephelauxetic and relativistic nephelauxetic series. Besides, the experimentally oriented non-relativistic and relativistic molecular orbital schemes of compound 6 were set up and compared with the results of previous model calculations on [Ln(COT)2]−, Pa(COT)2, and U(COT)2.
12/2008;
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ABSTRACT: The pseudohelical hydrocarbons (R)-6, (S)-7, and (R)-8 and the helical hydrocarbon (P)-9, formally derived from the helical hydrocarbon (P)-4 by stepwise replacement of each of the four-membered rings by a five-membered ring, have been prepared. Their optical rotations vary systematically, both in magnitude and sign. Of the extremes, (P)-4 represents the usual case of a right-handed dextrorotatory helix, while (P)-9 represents the unusual case of a right-handed levorotatory helix. To rationalize these facts, DFT calculations of the rotatory power of (P)-helices of three-, four-, and five-membered rings have been performed. The results show a very good agreement with the experimental data for the rigid helices of three-membered rings and always show the correct sign and order of magnitude for the flexible helices of four- and five-membered rings for which Boltzmann-averaged optical rotations of up to six conformers had to be used. Within the conformers of the latter, a set of large dihedral angles for the bonds of the inner sphere correspond to a high specific rotation, and a set of small dihedral angles correspond to a low specific rotation. As a consequence, the Boltzmann-averaged values markedly depend on the geometry and weight of the conformers involved.
The Journal of Organic Chemistry 12/2007; 72(24):9264-77. · 4.45 Impact Factor
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Annalen der Chemie und Pharmacie 07/2007; 2007(24):4081 - 4090. · 3.10 Impact Factor
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ABSTRACT: The first crystallographically characterized molybdenum(vi) selenoether complex [Mo(2)O(4)(OC(3)H(6)SeC(3)H(6)O)(2)] and its thioether analogue [Mo(2)O(4)(OC(3)H(6)SC(3)H(6)O)(2)] were synthesised. Their structural, electrochemical and oxygen atom transfer properties are compared. This is relevant for the molybdenum cofactors of the DMSO reductase family where the coordination of the active site metal occurs through O (serine/aspartate), S (cysteine) or Se (selenocysteine). Both structures are almost identical except for those parameters that are directly derived from the different sizes of the varied ligand atoms (Se and S). No trans influence was observed. The metal centered redox process (Mo(V)<-->Mo(VI)) is at slightly lower voltage for the sulfur than for the selenium complex. The selenium compound catalyses the oxygen atom transfer from DMSO to PPh(3) by a different mechanism and at a higher rate than the sulfur compound, which is an indication that cysteine and selenocysteine might be used for a purpose in the different molybdenum and tungsten cofactors.
Dalton Transactions 06/2007; · 3.84 Impact Factor
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ABSTRACT: Two single oxygen-bridged heterobimetallic oxides of Al(III) with group 4 metals (Ti, Hf) have been prepared. The reaction of LAlMeOH (1) [L = CH(N(Ar)(CMe))2, Ar = 2,6-iPr2C6H3] with dimethylmetallocenes of Ti and Hf in toluene (80 degrees C) and ether (room temperature), respectively, resulted in the formation of LAl(Me)(mu-O)M(Me)Cp2 [M = Ti (2), Hf (3)] in moderate to good yield. Compounds 2 and 3 were characterized by elemental analysis, IR, NMR (1H and 13C), EI-MS, and single-crystal X-ray structural analysis. Furthermore, compound 2 showed good catalytic activity in ethylene and styrene homopolymerization, while compound 3 is less active in ethylene polymerization. The styrene polymerization yields atactic polystyrene.
Inorganic Chemistry 03/2007; 46(4):1056-61. · 4.60 Impact Factor
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ABSTRACT: We report a facile route to the molecular compounds with the Mg-O-Al structural motif. The reaction of Mg[N(SiMe3)2]2 (1) with a stoichiometric amount of LAlOH(Me) (2) [L = CH{(CMe)(2,6-iPr2C6H3N)}2] in THF/n-hexane at 0 degrees C results in the formation of the heterobimetallic compound (Me3Si)2NMg(THF)2-O-Al(Me)L (3) in high yield. The similar reaction of 1 equiv of Mg[N(SiMe3)2]2 and 2 equiv of LAlOH(Me) results in the formation of trimetallic compound L(Me)Al-O-Mg(THF)2-O-Al(Me)L (4). Structural analyses of 3 and 4 have been carried out, revealing the presence of the Mg-O-Al motif. A tentative assignment of the Mg-O-Al vibrations has been made and was supported by calculations.
Journal of the American Chemical Society 11/2006; 128(40):13056-7. · 9.91 Impact Factor
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ABSTRACT: The reaction of LAl (L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3) or LAlH2 with PhB(OH)2 yields the unprecedented spirocyclic LAl[(OBPh)2O] compound. The former reaction proceeds under hydrogen formation and simultaneous oxidation of the aluminum(I).
Journal of the American Chemical Society 10/2006; 128(38):12406-7. · 9.91 Impact Factor
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ABSTRACT: Three novel aluminum-containing tin(IV) heterobimetallic sulfides are reported. The reaction of [LAl(SLi)2(THF)2]2 (1) [L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3] with Ph2SnCl2, Me2SnCl2, and SnCl4 in THF respectively afforded LAl(mu-S)2SnPh2 (2), LAl(mu-S)2SnMe2 (3), and LAl(mu-S)2Sn(mu-S)2AlL (4) in moderate yields. Compounds 2, 3, and 4 were characterized by elemental analysis, NMR, electron-impact mass spectrometry, and single-crystal X-ray structural analysis.
Inorganic Chemistry 05/2006; 45(8):3312-5. · 4.60 Impact Factor
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ABSTRACT: Reactions of LAl with ethyne, mono- and disubstituted alkynes, and diyne to aluminacyclopropene LAl[eta2-C2(R1)(R2)] ((L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3); R1 = R2 = H, (1); R1 = H, R2 = Ph, (2); R1 = R2 = Me, (3); R1 = SiMe3, R2 = C[triple bond]CSiMe3, (4)) are reported. Compounds 1 and 2 were obtained in equimolar quantities of the starting materials at low temperature. The amount of C2H2 was controlled by removing an excess of C2H2 in the range from -78 to -50 degrees C. Compound 4 can be alternatively prepared by the substitution reaction of LAl[eta2-C2(SiMe3)2] with Me3SiC[triple bond]CC[triple bond]CSiMe3 or by the reductive coupling reaction of LAlI2 with potassium in the presence of Me3SiC[triple bond]CC[triple bond]CSiMe3. The reaction of LAl with excess C2H2 and PhC[triple bond]CH (<1:2) afforded the respective alkenylalkynylaluminum compounds LAl(CH=CH2)(C[triple bond]CH) (5) and LAl(CH=CHPh)(C[triple bond]CPh) (6). The reaction of LAl(eta2-C2Ph2) with C2H2 and PhC[triple bond]CH yielded LAl(CPh=CHPh)(C[triple bond]CH) (7) and LAl(CPh=CHPh)(C[triple bond]CPh) (8), respectively. Rationally, the formation of 5 (or 6) may proceed through the corresponding precursor 1 (or 2). The theoretical studies based on DFT calculations show that an interaction between the Al(I) center and the C[triple bond]C unit needs almost no activation energy. Within the AlC2 ring the computational Al-C bond order of ca. 1 suggests an Al-C sigma bond and therefore less pi electron delocalization over the AlC2 ring. The computed Al-eta2-C2 bond dissociation energies (155-82.6 kJ/mol) indicate a remarkable reactivity of aluminacyclopropene species. Finally, the 1H NMR spectroscopy monitored reaction of LAl(eta2-C2Ph2) and PhC[triple bond]CH in toluene-d8 may reveal an acetylenic hydrogen migration process.
Journal of the American Chemical Society 04/2006; 128(15):5100-8. · 9.91 Impact Factor
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Angewandte Chemie International Edition 04/2006; 45(14):2277-80. · 13.45 Impact Factor
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ABSTRACT: A series of Al(III) compounds containing the C6F5-substituted beta-diketiminate ligands LAlMeCl (2), LAlMe2 (3), LAlMeI (4), and LAlBr2 (5) (L = HC[(CMe)(NC6F5)]2) were synthesized and characterized. The hydrolysis of 2 and 4 in the presence of 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene as the hydrogen halide acceptor both lead to (LAlMe)2(mu-O) (6), a methylalumoxane derivative, which is the first hydrolysis product with the general formula of (RAlMe)(n)O. A comparison of the hydrolysis products of 2 and 4 with that of L'AlMeCl (L' = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3) shows that with the C6F5-substituted beta-diketiminate ligand, it was not possible to generate LAlMe(OH). This is obviously due to the stronger Brönsted acidity of the proton and the smaller size of the C6F5 group in this compound compared to that of the corresponding 2,6-iPr2C6H3 derivative.
Inorganic Chemistry 03/2006; 45(4):1823-7. · 4.60 Impact Factor
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ABSTRACT: A series of organometallic compounds of group 13 metals supported by the sterically encumbered beta-diketiminate ligand containing hydrides, fluorides, chlorides, and bromide have been synthesized and structurally characterized. The synthetic strategy applied utilizes halide metathesis and reduction of metal chlorides to the corresponding hydrides. Thus, the reaction of LLi.OEt2 with MeMCl2 affords LM(Me)Cl (M = Al (1), Ga (2), In (3)) and LGaBr2 (4) with GaBr3. Reduction of LGa(Me)Cl with LiH.BEt3 leads to the formation of LGa(Me)H (10). Synthesis of LGaH(2) (12) has been accomplished by reacting LGaI2 (8) with LiH.BEt3. LAl(Me)Cl (1) and LAlH2 (6) have been converted to LAl(Me)F (5) and LAlF2 (7), respectively. The former was obtained in a reaction of LAl(Me)Cl with Me3SnF while the latter was isolated in a reaction of LAlH2 with BF3.OEt2. Similarly reaction of LGaI2 (8) with Me3SnF affords LGaF2 (9). Compounds reported herein have been characterized by elemental analyses, IR, NMR, EI-MS, and single-crystal X-ray diffraction techniques.
Inorganic Chemistry 03/2006; 45(4):1853-60. · 4.60 Impact Factor
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ABSTRACT: The reactions of potassium Rf-amide [Rf = tris(trifluoromethyl)phenyl](2) with PCl3, AsC13, and GeC12 · dioxane yield new four-membered inorganic heterocycles [RfNPCl]2(3), [RfNAsC1]2(4), and [RfNGe]2(5), respectively. On the other hand, the reaction of Rf-amide 2 with two equivalents of RfPCl2 leads to the formation of the imino-γ3-phosphane RfN=PRf(6) and the diamino-γ3-phosphane (RfNH)2PRf(7). The iminophosphane 6 reacts with Ni(CO)2(PPh3)2 and forms the complex [Ni(PPh3)2(RfN=PRf)] (9), in which the imino- phosphane coordinates to the metal through the phosphorus lone pair. Treatment of lithium amide 2 with transition metal chlorides ZnCl2 and FeCl2 yields the imido/amido spirocyclic metal derivatives 9 and 10, respectively. Compounds 3–10 have been extensively characterized by their analytical and mass, IR, and NMR (1H, 19F, and 31P) spectroscopy. Further, the molecular structures of all the compounds have been unambiguously determined by single-crystal X-ray diffraction studies. The diazadigermetidine 5 crystallizes in a fluorescent-yellow orthorhombic and a yellow monoclinic crystal modification. The results obtained reveal the role of Rf, group in stabilizing new multiple bonded systems and inorganic heterocycles. A skeletal rearrangment of the Rf ligand is observed in the reactions leading to compounds 9 and 10. Moreover, the preparation of compounds 9 and 10 indicates the limitation of the use of this ligand in the preparation of new metal-amide systems, especially where the metal atoms have a strong tendency for the formation of strong MF bonds.
Berichte der deutschen chemischen Gesellschaft 01/2006; 130(8):1113 - 1121. · 2.94 Impact Factor
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ABSTRACT: Ausgehend von FcPCl2 (1), FcPH2 (2), FcAsCl2 (3) und Fe(C5H4AsCl2)2 (4) werden drei-, vier-, fünf- und achtgliedrige Heterocyclen mit Ferrocenyl-Substitutenten synthetisiert (Fc = Ferrocenyl). Durch Umsetzung von 1 mit 2 in Gegenwart von DBU entsteht (FcP)n, das mit (Ph3P)2Pt(C2H4) zu (7) reagiert. Der analoge As2Pt-Ring 9 ist über (FcAs)3 (8) in guter Ausbeute zugänglich. Die Reduktion von 1 mit LiAlH4 liefert (FcP)4 (10). Ein fünfgliedriger Arsen-Schwefel-Heterocyclus, Fc2As2S3 (12), entsteht durch Umsetzung von FcAs=P(2,4,6-tBu3C6H2) (11) mit Schwefel. FcAsCl2 (3) reagiert mit Me3SiNSNSiMe3 zu FcAs(NSN)2AsFc (13), das einen achtgliedrigen As2S2N4-Ring enthält. Dessen Komplexierung mit (Norbornadien)M(CO)4 führt zu den Tetracarbonyl-Komplexen [FcAs(NSN)2AsFc]M(CO)4 (14, 15; M = Cr, Mo). Ein Arsenüberbrücktes Ferrocenophan 16 kann bei der Reaktion von Fe(C5H4Li)2 × TMEDA mit AsCl3 isoliert werden. Auch die Umsetzung von 4 mit Me3SiNSNSiMe3 liefert ein kondensiertes Ferrocenophan-Derivat der Zusammensetzung (C5H4)2FeAs2N6S4 (17). Die Molekülstrukturen von 13 und 17 wurden röntgenographisch bestimmt.Inorganic Ring System Containing Ferrocenyl SubstituentsThree-, four-, five-, and eight-membered heterocycles are synthesized starting from FcPCl2 (1), FcPH2 (2), FcAsCl2 (3) and Fe(C5H4AsCl2)2 (4) (Fc = Ferrocenyl). Treatment of 1 with 2 in the presence of DBU yields (FcP)n, which reacts with (Ph3P)2Pt(C2H4) to give (7). The corresponding As2Pt ring system 9 is available in high yield via (FcAs)3 (8). The reduction of 1 with LiAlH4 yields (FcP)4 (10). A five-membered arsenic sulfur heterocycle, Fc2As2S3 (12), is formed in the reaction of FcAs=P(2,4,6-tBu3C6H2) (11) with sulfur. FcAsCl2 (3) reacts with Me3SiNSNSiMe3 to give FcAs(NSN)2AsFc (13), which contains an eight-membered As2S2N4 ring. Its complexation with (norbornadiene)M(CO)4 leads to the tetracarbonyl complexes [FcAs(NSN)2AsFc]M(CO)4 (14, 15; M = Cr, Mo). An arsenic-bridged ferrocenophane 16 can be isolated from the reaction of Fe(C5H4Li)2 x TMEDA with AsCl3. The reaction of 4 with Me3SiNSNSiMe3 also produces a condensed ferrocenophane derivative, (C5H4)2FeAs2N6S4 (17). The molecular structures of 13 and 17 have been determined by X-ray diffraction.
Berichte der deutschen chemischen Gesellschaft 01/2006; 122(7):1247 - 1254. · 2.94 Impact Factor
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ABSTRACT: The silanediols RN(SiMe3)Si(OSiMe3)(OH)2 (R = 2,4,6-Me3C6H24, 2,6-Me2C6H35, and 2,6-iPr2C6H36) were prepared by the reactions of the respective silanetriols RN(SiMe3)-Si(OH)31 – 3 with SiMe3Cl in THF/hexane. Silanetriol 1 in CH2Cl2/hexane solution converts over a period of 4 weeks into the silanediol (2,4,6-Me3C6H2)N(SiMe3)Si(OSiMe2 R)-(OH)2 [R = CH2(2-NH2-3,5-Me2C6H2)] (7). Compounds 4 – 7 were characterized by means of mass, IR and NMR (1H and 29Si) spectroscopy. Additionally, the molecular structures of 4 and 7 were determined by single-crystal X-ray diffraction studies. Compound 4 forms O H…O hydrogen-bonded tetramers in the solid state. A nine-membered ring formed by an intermolecular OH…N hydrogen bond is found in the solid-state structure of 7.
Berichte der deutschen chemischen Gesellschaft 01/2006; 129(4):391 - 395. · 2.94 Impact Factor
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ABSTRACT: Syntheses and Structures of Cyclic and Acyclic Compounds Containing Vanadium(V) and Molybdenum(VI)The reaction of (C2F5)2P(Cl)NSiMe3 (2) with Cl3VNSiMe3 in CH2Cl2 yields the eight-membered ring [(C2F5)2PN2VCl2]2 (3). (CF3)2P(Cl)NSiMe3 (1) reacts with VOCl3 to form the eight-membered ring [(CF3)2PN]3NVCl2 (4). A six-membered ring [Ph2PN]2NVCl2 (5) can be isolated from the reaction of Ph2P(Cl)NSiMe3 with VOCl3. 1 reacts quantitatively with MoO2Cl2 and MoOCl4 to form [MoOCl3-O-P(CF3)2N-SiMe3]4 (6) and (CF3)2P(Cl)N-MoOCl3 (7), respectively. The molecular structures of 3, 5, and 6 have been determined by X-ray diffraction.
Berichte der deutschen chemischen Gesellschaft 01/2006; 124(12):2655 - 2661. · 2.94 Impact Factor
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ABSTRACT: Synthesis and Structures of (Monoorganyl)amides and -imides of Zirconium and HafniumThe tetrahalides MCl4 (M = Zr 1 a, Hf 1 b) react with LiNHtBu with elimination of LiCl to yield [(tBuNH)2MNtBu]2 (3) (M = Zr 3a, Hf 3b). Compounds 3 are thermally instable and oli-gomerise above 100 °C with elimination of H2NtBu. The reactions of (η5-C5Me5)MCl3 (M = Zr 1 c, Hf 1 d) with LiNHR (R = tBu 2 a,2,4,6-Me3C6H22 b, 2, 6-iPr2C6H32 c) lead to (η5-C5Me5)M(NHR)3 (4) (R = tBu, M = Zr 4 a, Hf 4 b; R = 2, 4,6-Me3C6H2, M = Zr 4 c, Hf 4 d; R = 2,6-iPr2C6H3, M = Zr 4 e, Hf 4 f). Compounds 4 are thermally very stable and melt without decomposition. When 1 c and 1 d react with LiNHPh (2 d), dimers of composition [(η5-C5Me5)M(NHPh)NPh]2 (M = Zr 5 a, Hf 5 b) are obtained. The complexes (η5-C5Me5)2MCl2 (M = Zr 1 e, Hf 1 f) react with 2 b to form (η5-C5Me5)2M(NHR)2 (6) (M = Zr 6 a, Hf 6 b). Pyridine reacts with 4 e at 85 °C and replaces one molecule of 2,6-iPr2C6H3NH2 to give (η5-C5Me5)Zr-(NHR)NR · Py (7). The single crystal X-ray structures of 4 a, 4 f, 5 b and 7 are described.
Berichte der deutschen chemischen Gesellschaft 01/2006; 125(4):825 - 831. · 2.94 Impact Factor
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ABSTRACT: Function of Di(tert-butyl)silanediolate as an Anchor for Metal Fragments in High and Medium Oxidation States. Synthesis and Structures of (tBu)2SiO2(TeCl2 – μ-Cl2 – TeCl2) and (tBu)2Si(OReO3))2The compounds (tBu)2SiO2(TeCl2 – μ-Cl2 – TeCl2) (2) and (tBu)2Si(OReO3)2 (3) have been prepared by the reactions of (tBu)2Si(OH)2 (1) with TeCl4 and Re2O7. The single-crystal X-ray structures of 2 and 3 are reported. The (tBu)2SiO2 group functions as an anchor for the metal fragments TeCl3 and ReO3.
Berichte der deutschen chemischen Gesellschaft 01/2006; 124(3):519 - 521. · 2.94 Impact Factor
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Annalen der Chemie und Pharmacie 01/2006; 1996(6):899 - 911. · 3.10 Impact Factor
