Search results for "force"
showing 10 items of 3423 documents
Synthesis of chiral β-disulfoxides and their racemization with strong bases
1997
Abstract β-Disulfoxides can be obtained from different α-sulfunylcarbanions and sulfinates. While α-unsubstituted and monosubstituted β-disulfoxides are configurationally stable in the presence of strong bases, α,α-disubstituted β-disulfoxides epimerize through an intermolecular mechanism.
New strategies in the development of polynuclear complexes. Crystal structure of the tetranuclear copper(II) complex [Cu4(L1)2(OH)4Cl2(H2O)2]2(H3O2)(…
2000
Abstract The preparation and interaction of the new polyaza[n]naphthalenophanes 2,5,8,11-tetraaza[12](1,4)naphthalenophane (L1) and 2,6,9,13-tetraaza[14](1,4)naphthalenophane (L2) with hydrogen ions and Cu2+ is described. The crystal structure of the new tetranuclear copper(II) complex [Cu4(L1)2(OH)4Cl2(H2O)2]2(H3O2)(ClO4)2Cl·2H2O (L1=2,5,8,11-tetraaza[12](1,4)naphthalenophane) is presented and discussed. A variety of intra- and intermolecular forces contribute to the particular organisation of the crystal. The solution studies indicate the formation of similar tetranuclear species for L1 while for L2 just mononuclear 1:1 species are detected.
Magneto-structural studies on heterobimetallic malonate-bridged M(II)Re(IV) complexes (M = Mn, Co, Ni and Cu).
2010
The mononuclear Re(IV) compound of formula (PPh(4))(2)[ReBr(4)(mal)] (1) was used as a ligand to obtain the heterobimetallic species [ReBr(4)(μ-mal)Co(dmphen)(2)]· MeCN (2), [ReBr(4)(μ-mal)Ni(dmphen)(2)] (3), [ReBr(4)(μ-mal)Mn(dmphen)(2)] (4a), [ReBr(4)(μ-mal)Mn(dmphen)(H(2)O)(2)]·dmphen·MeCN·H(2)O (4b), [ReBr(4)(μ-mal)Cu(phen)(2)]·1/4H(2)O (5) and [ReBr(4)(μ-mal)Cu(bipy)(2)] (6) (mal = malonate dianion, dmphen = 2,9-dimethyl-1,10-phenanthroline, phen = 1,10-phenanthroline and bipy = 2,2'-bipyridine). The structures of 2 and 5 (single-crystal X-ray diffraction) are made up of neutral [ReBr(4)(μ-mal)M(AA)] dinuclear units [AA = dmphen with M = Co (2) and AA = phen with M = Cu (5)] where the …
N-methyl-1,2-dihydro-2-benzoylmethylenequinolines: configurational dissimilarity with unmethylated congeners
2000
Abstract Twelve 1-methyl-1,2-dihydro-2-benzoylmethylenequinolines have been synthesized and their structures elucidated by 1 H, 13 C and 15 N NMR, UV–Vis and X-ray methods. The results unambiguously show that these compounds and the corresponding 1,2-dihydro-2-benzoylmethylenequinolines both in crystalline and in solution state are the Z and E isomers, respectively. Comparison of the X-ray structures reveal that ( Z )-1,2-dihydro-2-benzoyl-methylenequinolines are less twisted as compared to their 1-methyl derivatives. This difference is caused by formation of the quasi-aromatic six-membered ring stabilized by an intramolecular hydrogen bond in unmethylated congeners, prevented by N -methyla…
Synthesis, Structural, Thermal and Magnetic Characterization of a Pyrophosphato‐Bridged Cobalt(II) Complex
2008
The reaction in water of CoII sulfate heptahydrate with 1,10-phenanthroline (phen) and sodium pyrophosphate (Na4P2O7) in a 2:4:1 stoichiometric ratio resulted in the crystallization of a neutral dinuclear CoII complex, {[Co(phen)2]2(μ-P2O7)}·6MeOH (1), as revealed by a single-crystal X-ray diffraction study. The bridging pyrophosphato ligand between the two [Co(phen)2]2+ units in a bis(bidentate) coordination mode places the adjacent metal centers at 4.857 A distance, and its conformation gives rise to intramolecular π–π stacking interaction between adjacent phen ligands. Indeed, intermolecular π–π stacking interactions between phen ligands from adjacent dinuclear complexes create a supramo…
Synthesis, crystal structures and magnetic properties of cyanide- and phenolate-bridged [MIIINiII]2tetranuclear complexes (M = Fe and Cr)
2005
The binuclear complex NiII2L(H2O)2(ClO4)2 (1) and the neutral tetranuclear bimetallic compounds [{MIII(phen)(CN)4}2{NiII2L(H2O)2}]·2CH3CN with M = Fe (2) and Cr (3) [H2L = 11,23-dimethyl-3,7,15,19-tetraazatricyclo[19.3.1.19,13]hexacosa-2,7,9,11,13(26),14,19,21(25),22,24-decaene-25,26-diol] have been synthesized and the structures of 2 and 3 determined by single crystal X-ray diffraction. 2 and 3 are isostructural compounds whose structure is made up of centrosymmetric binuclear cations [Ni2(L)(H2O)2]2+ and two peripheral [M(phen)(CN)4]− anions [M = Fe (2) and Cr (3)] acting as monodentate ligands towards the nickel atoms through one of their four cyanide nitrogen atoms. The environment of t…
A Novel Dinuclear Fe II Spin‐Crossover Complex Based on a 2,2‐Bipyrimidine Bridge Ligand: [Fe(CH 3 bipy)(NCS) 2 ] 2 bpym
2004
The dinuclear iron(II) complex {[Fe(CH3bipy)(NCS)2]2bpym} has been synthesised and its crystal structure determined at 293 K. The magnetic properties display intramolecular antiferromagnetic coupling at 1 bar (J = −4.2 cm−1), and the onset of a pressure-induced spin conversion is observed at 11 kbar. Magnetic field Mossbauer measurements have been carried out at 4.2 K, and indicate that the HS species correspond to [HS-HS] pairs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Conformation versus coordination: synthesis and structural investigations of tellurium(II) dithiolates derived from beta-donor-substituted thiols.
2002
New methods of preparing tellurium(II) dithiolates, Te(SR)(2), are presented. Te(SCH(2)CH(2)OAc)(2), 1, was made from Te(SCH(2)CH(2)OH)(2) by acetylation of the hydroxyl groups. Te(SCH(2)CH(2)SAc)(2), 2, [Te(SCH(2)CH(2)NH(3))(2)]Cl(2), 3, and Te(SC(6)H(4)(o-NH(2)))(2), 4, were synthesized by ligand exchange reactions of Te(S(t)Bu)(2) with 2 equiv of HSCH(2)CH(2)SAc, [HSCH(2)CH(2)NH(3)]Cl, and HSC(6)H(4)(o-NH(2)), respectively. Of all compounds, 4 exhibits the strongest thermal sensitivity toward decomposition and the largest low-field shift of the (125)Te NMR signal, two features that are attributed to weak Te.N interactions. The structural parameters of the CSTeSC unit exhibit very similar…
Unexpected magnetic topology in the heterobimetallic [ReIVBr4(μ-ox)CuII(bpy)2] compound
2011
Abstract A novel oxalato-bridged rhenium(IV)-copper(II) compound, namely [ReIVBr4(μ-ox)CuII(bpy)2] (1), has been obtained by reacting (PPh4)2[ReBr4(ox)] with Cu(CF3SO3)2 and 2,2′-bpy in CH3CN, and its crystal structure determined by single-crystal X-ray diffraction. Intermolecular Br⋯Br interactions and nonbonding Cu⋯Br type contacts between the heterobimetallic dinuclear units lead to a two-dimensional supramolecular structure. Compound 1 behaves magnetically as a [ReIVCuII]2 tetranuclear species with weak antiferromagnetic interactions through the oxalato bridge and intermolecular Br⋯Br contacts.
Magnetic properties and molecular structures of binuclear (2-pyrazinecarboxylate)-bridged complexes containing Re(iv) and M(ii) (M = Co, Ni)
2007
Three novel Re(iv) compounds, the mononuclear complex Bu(4)N[ReBr(5)(Hpyzc)] (1) and the heterobimetallic complexes [ReBr(5)(mu-pyzc)M(dmphen)(2)].2CH(3)CN [M = Co (2), Ni (3)] (Hpyzc = 2-pyrazinecarboxylic acid, dmphen = 2,9-dimethyl-1,10-phenanthroline), have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. The structure of 1 consists of [ReBr(5)(Hpyzc)](-) complex anions and tetrabutylammonium cations, Bu(4)N(+). The Re(iv) is surrounded by five bromide anions and a N-donor Hpyzc monodentate ligand, in a distorted octahedral environment. The structures of 2 and 3 consist of dinuclear units [ReBr(5)(mu-pyzc)M(dmphen)(2)], with the metal ions li…