Home About us Contact
|
Home About us Contact | ||
|
|
||
Single-crystal X-ray Structure Analysis (single-crystal + x-ray_structure_analysis)
Selected AbstractsSynthesis and Characterization of Novel Titanium, Germanium, and Tin Silazane Complexes Bearing a Cyclohexasilazanetriido LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2007Christian Lehnert Abstract Novel heterometallic silazane complexes were synthesized by the reaction of 1-lithio-2,2,4,4,6,6-hexamethylcyclotrisilazane Li(HMCTS)H2 with the tetrachloride salts of titanium and germanium as well as by the reaction of 1,1,3,3,5,5-hexamethylcyclotrisilazane H3(HMCTS) with tin tetrachloride and excess triethylamine. The products [H3(DMCHS)TiCl] (1), [H3(DMCHS)GeCl] (2), and [H3(DMCHS)SnCl] (3) {H3(DMCHS) = 2,2,4,4,6,6,8,8,10,10,12,12-dodecamethylcyclohexasilazane-1,5,9-triido} were characterized by 1H-, 13C-, 14N-, and 29Si NMR spectroscopy, elemental analyses and single-crystal X-ray structure analyses. The complexes have a surprising and interesting structure, that of a new dodecamethylcyclohexasilazane system with the Ti, Ge, or Sn atom in the center. These metal atoms are coordinated by one chlorine atom and three nitrogen atoms. The metal centers are part of three six-membered hetero-silazane rings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Molecular Structures and NMR Studies of Lithium and Germanium(II) Complexes of a New Chelating Amido,Imino Ligand Obtained by Addition of nBuLi to 1,2-Bis(arylimino)acenaphthene,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2006Igor L. Fedushkin Abstract The reaction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian, 1) with 1 equiv. of nBuLi in diethyl ether or with 2 equiv. of nBuLi in hexane produces [{dpp-bian(nBu)}Li(Et2O)] (3) and [{dpp-bian(nBu)Li}nBuLi]2 (4), respectively. Complexes 3 and 4 are formed by the transfer of an nBu anion to one of the imine carbon atoms of the dpp-bian ligand. Treatment of 3 and 4 with H2O affords the C -alkylated N -protonated amino-imino compound dpp-bian(H)(nBu) (5). The reaction of 3 with GeCl2(dioxane) affords the three-coordinate germylene complex [{dpp-bian(nBu)}GeCl] (6). The molecular structures of 3,6 were determined by single-crystal X-ray structure analysis. The lack of symmetry in the alkylated bian system in 3,6 causes the non-equivalence of all protons except those of the CH3 groups of the iPr substituents. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] An iterative strategy for the synthesis of oligothiophenes by catalytic cross-coupling reactionsHETEROATOM CHEMISTRY, Issue 2 2004Thomas Pinault An iterative strategy for the synthesis of new sulfur-functionalized oligothiophenes by Suzuki or Stille cross-coupling reactions was applied to the reaction of 4-bromo-tert-butylphenylthioether with thiophene derivatives. The planarity of the oligothiophenes obtained was confirmed by the single-crystal X-ray structure analysis of 2-(4,-tert-butylthiophenyl)thiophene, which shows a potentially large electronic conjugation length. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:121,126, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10224 [source] The reaction of 3,4-dihydro-2H-pyran with oxalyl chloride: Formation and crystal structure analysis of an unexpected bicyclic productJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2010Bernd Schmidt 3,4-Dihydro-2-H-pyran and oxalyl chloride react, depending on the conditions, to keto esters, a pyran-3-carboxylic acid or derivatives thereof, or to an hitherto unknown bicyclic acetal containing a vinyl chloride moiety. The structure of the latter product has been unambiguously elucidated by single-crystal X-ray structure analysis. A mechanism for its formation is proposed. J. Heterocyclic Chem., (2010). [source] 1-(,-Aminobenzyl)-2-naphthol: A New Chiral Auxiliary for the Synthesis of Enantiopure ,-Aminophosphonic AcidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2009Kirill Abstract Ooh Betti! A new diastereoselective synthesis of ,-aminophosphonates has been developed based on the reaction of trialkyl phosphites with chiral imines derived from (R)- or (S)-1-(,-aminobenzyl)-2-naphthol (Betti base; see scheme, X=H, CH3, or Br). The reaction proceeds with high diastereoselectivity. Treatment with HCl results in the formation of the desired ,-aminophosphonic acids. A new diastereoselective synthesis of ,-aminophosphonates has been developed, based on the reaction, in the presence of trifluoroacetic acid, of trialkyl phosphites with chiral imines derived from (R)- or (S)-1-(,-aminobenzyl)-2-naphthol. The reaction proceeds at room temperature in toluene with high diastereoselectivity. The major diastereomer can be separated by crystallization from an appropriate solvent. The relative configuration of both chiral centers of the major diastereomer was determined by single-crystal X-ray structure analysis. The desired ,-aminophosphonic acids can be obtained in enantiopure form by treatment of the corresponding diastereomers with HCl. [source] Mixed-Transition-Metal Acetylides: Synthesis and Characterization of Complexes with up to Six Different Transition Metals Connected by Carbon-Rich Bridging UnitsCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2008Rico Packheiser Dipl.-Chem. Abstract The synthesis and reaction chemistry of heteromultimetallic transition-metal complexes by linking diverse metal-complex building blocks with multifunctional carbon-rich alkynyl-, benzene-, and bipyridyl-based bridging units is discussed. In context with this background, the preparation of [1-{(,2 -dppf)(,5 -C5H5)RuCC}-3-{(tBu2bpy)(CO)3ReCC}-5-(PPh2)C6H3] (10) (dppf=1,1,-bis(diphenylphosphino)ferrocene; tBu2bpy=4,4,-di- tert -butyl-2,2,-bipyridyl; Ph=phenyl) is described; this complex can react further, leading to the successful synthesis of heterometallic complexes of higher nuclearity. Heterotetrametallic transition-metal compounds were formed when 10 was reacted with [{(,5 -C5Me5)RhCl2}2] (18), [(Et2S)2PtCl2] (20) or [(tht)AuCC-bpy] (24) (Me=methyl; Et=ethyl; tht=tetrahydrothiophene; bpy=2,2,-bipyridyl-5-yl). Complexes [1-{(,2 -dppf)(,5 -C5H5)RuCC}-3-{(tBu2bpy)(CO)3ReCC}-5-{PPh2RhCl2(,5 -C5Me5)}C6H3] (19), [{1-[(,2 -dppf)(,5 -C5H5)RuCC]-3-[(tBu2bpy)(CO)3ReCC]-5-(PPh2)C6H3}2PtCl2] (21), and [1-{(,2 -dppf)(,5 -C5H5)RuCC}-3-{(tBu2bpy)(CO)3ReCC}-5-{PPh2AuCC-bpy}C6H3] (25) were thereby obtained in good yield. After a prolonged time in solution, complex 25 undergoes a transmetallation reaction to produce [(tBu2bpy)(CO)3ReCC-bpy] (26). Moreover, the bipyridyl building block in 25 allowed the synthesis of Fe-Ru-Re-Au-Mo- (28) and Fe-Ru-Re-Au-Cu-Ti-based (30) assemblies on addition of [(nbd)Mo(CO)4] (27), (nbd=1,5-norbornadiene), or [{[Ti](,-,,,-CCSiMe3)2}Cu(NCMe)][PF6] (29) ([Ti]=(,5 -C5H4SiMe3)2Ti) to 25. The identities of 5, 6, 8, 10,12, 14,16, 19, 21, 25, 26, 28, and 30 have been confirmed by elemental analysis and IR, 1H, 13C{1H}, and 31P{1H} NMR spectroscopy. From selected samples ESI-TOF mass spectra were measured. The solid-state structures of 8, 12, 19 and 26 were additionally solved by single-crystal X-ray structure analysis, confirming the structural assignment made from spectroscopy. [source] Highly Selective Hydrogenation of Carbon,Carbon Multiple Bonds Catalyzed by the Cation [(C6Me6)2Ru2(PPh2)H2]+: Molecular Structure of [(C6Me6)2Ru2(PPh2)(CHCHPh)H]+, a Possible Intermediate in the Case of Phenylacetylene HydrogenationCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2007Mathieu J.-L. Abstract The dinuclear cation [(C6Me6)2Ru2(PPh2)H2]+ (1) has been studied as the catalyst for the hydrogenation of carbon,carbon double and triple bonds. In particular, [1][BF4] turned out to be a highly selective hydrogenation catalyst for olefin functions in molecules also containing reducible carbonyl functions, such as acrolein, carvone, and methyljasmonate. The hypothesis of molecular catalysis by dinuclear ruthenium complexes is supported by catalyst-poisoning experiments, the absence of an induction period in the kinetics of cyclohexene hydrogenation, and the isolation and single-crystal X-ray structure analysis of the tetrafluoroborate salt of the cation [(C6Me6)2Ru2(PPh2)(CHCHPh)H]+ (2), which can be considered as an intermediate in the case of phenylacetylene hydrogenation. On the basis of these findings, a catalytic cycle is proposed which implies that substrate hydrogenation takes place at the intact diruthenium backbone, with the two ruthenium atoms acting cooperatively in the hydrogen-transfer process. [source] Polymorphism Versus Thermochromism: Interrelation of Color and Conformation in Overcrowded Bistricyclic Aromatic EnesCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2006P. Ulrich Biedermann Dr. Abstract The nature of the thermochromic form of overcrowded bistricyclic aromatic enes (BAEs) has been controversial for a century. We report the single-crystal X-ray structure analysis of the deep-purple and yellow polymorphs of 9-(2,7-dimethyl-9H -fluoren-9-ylidene)-9H -xanthene (11), which revealed the molecules in a twisted and a folded conformation, respectively. Therefore, the deeply colored thermochromic form B of BAEs is identified as having a twisted conformation and the ambient-temperature form A as having a folded conformation. This relationship between the color and the conformation is further supported by the X-ray structures of the deep-purple crystals of the twisted 9-(9H -fluoren-9-ylidene)-9H -xanthene (10), and of the yellow crystals of the folded 9-(11H -benzo[b]fluoren-11-ylidene)-9H -xanthene (12). Based on this conclusive crystallographic evidence, eleven previously proposed rationales of thermochromism in BAEs are refuted. In the twisted structures, the tricyclic moieties are nearly planar and the central double bond is elongated to 1.40 Å and twisted by 42°. In the folded structures, the xanthylidene moieties are folded by 45° and the fluorenylidene moieties by 18,20°. Factors stabilizing the twisted and folded conformations are discussed, including twisting of formal single or double bonds, intramolecular overcrowding, and the significance of a dipolar aromatic "xanthenylium-fluorenide" push,pull structure. [source] | ||||||||||