Search results for "Dimer"
showing 10 items of 558 documents
CCDC 252683: Experimental Crystal Structure Determination
2006
Related Article: R.D.Willett, C.J.Gomez-Garcia, B.L.Ramakrishna, B.Twamley|2005|Polyhedron|24|2232|doi:10.1016/j.poly.2005.03.088
CCDC 252684: Experimental Crystal Structure Determination
2006
Related Article: R.D.Willett, C.J.Gomez-Garcia, B.L.Ramakrishna, B.Twamley|2005|Polyhedron|24|2232|doi:10.1016/j.poly.2005.03.088
Stepwise synthesis and selective dimerisation of bis- and trisloop tetra-urea calix[4]arenes.
2008
Tetra-urea calix[4]arenes substituted with four mono- or bisalkenyl residues have been converted into bis- or tetraloop compounds by intramolecular olefin metathesis, with use of a tetratosylurea calix[4]arene as template. The same strategy has now been used to synthesise trisloop compounds and bisloop compounds with adjacent loops, completing the series of the loop-containing tetra-urea derivatives. A tetra-urea calix[4]arene of the AABB type, where A stands for a bisalkenyl- and B for a monoalkenyl-substituted urea unit, was used as precursor for the three loops. It was easily synthesised from a tetraamino calix[4]arene in which two adjacent amino groups were Boc-protected. The ABCB-type …
The yttrium chloride-1,10-phenanthroline interaction: Synthesis and X-ray crystal structure of the complex [Y(OH)(H2O)2(phen)2]2Cl4·2(phen)·MeOH
1991
Abstract Investigations on the reaction between YCl3·H2O and phen (1,10-phenanthroline) led to the isolation of the title compound. The synthesis, IR and X-ray structural characterization are described. The crystal contains centrosymmetric binuclear dications [Y2(phen)4(μ-OH)2(H2O)4]4+, uncoordinated chloride anions, two clathrated phen molecules and a disordered methanol molecule. The yttrium ions are eight-coordinated with square antiprismatic geometry to the nitrogen atoms of two phen molecules, to bridging hydroxyl groups and to two water molecules. The Y ⋯ YI separation in the dimer is 3.651(2)A˚.
On the dimerization of the primitive tRNAs: implications in the origin of genetic code.
2002
RNAs that catalyse their own aminoacylation have been recently selected in vitro. These findings support the notion that the primitive aminoacyl-tRNA synthetases may have been RNAs. In this paper, we propose a structural model for the first aminoacyl-tRNA synthetase consisting of an RNA complex formed between two primitive tRNA molecules through two intermolecular loop-strand interactions, and with implications in the origin of the genetic code.
Mono- and di-nuclear complexes of ortho-palladated and -platinated 4,4′-dimethylazobenzene with bis(diphenylphosphino)methane. More data on transphob…
2002
Abstract Complexes [Pd(κ2-R)(μ-Cl)]2 [κ2-R=κ2-C,N′-C6H3(NNC6H4Me-4′)-2-Me-5 (1)] and [Pd(κ1-R)Cl(κ1-dppm)(κ2-dppm)]TfO [dppm=bis(diphenylphosphino)methane (2)] have been used to prepare new palladium derivatives containing dppm. Thus, complex 1 reacts with one equivalent of dppm to afford [{Pd(κ2-R)Cl}2(μ-dppm)] (3) and with AgClO4 and dppm (1:2:2 molar ratios) to give [Pd(κ2-R)(κ2-dppm)]ClO4 (4·ClO4). The triflate salt of this complex (4·TfO) reacts with PPh3 to yield [Pd(κ1-R)(PPh3)(κ2-dppm)]TfO (5). Dinuclear complexes were obtained by reacting 2, (i) with [AuCl(PPh3)] or [AuCl(tht)] (tht=tetrahydrothiophene) (1:1, −60 °C) and (ii) with 1 (2:1) to give, respectively, [Pd(κ1-R)Cl(μ-dppm…
Crystal structure, magnetic and spectroscopic properties of the bis(dimethyl sulfoxide) adduct of tetra-μ-formato-dicopper(II), a new tetracarboxylat…
1994
The crystal and molecular structure of a new tetracarboxylato-bridged copper(II) dimer, the bis(dimethyl sulfoxide)tetrakis(μ-formato)dicopper(II) has been determined by X-ray diffraction methods. It crystatlizes in the tetragonal space group I41/a, with Z=8 in a cell of dimensions a=17.688(2), c=10.408(1) Å. The structure is built up of centrosymmetric neutral dimers [Cu2(HCOO)4(dmso)2], where four bidentate carboxylate anions form syn-syn bridges between the metal atoms which are in a 4 + 1 environment. Magnetic susceptibility data show that the copper atoms are strongly antiferromagnetically coupled with J=-434 cm-1. The obtained triplet-singlet energy gap is compared with those reported…
Enlarging the family of ferrocenylphosphine dinuclear rhodium complexes: synthesis and X-ray structure of a novel “A-frame”-type trimetallic Rh/Fe/Rh…
2004
Abstract The symmetrically substituted ligand 1,1 ′ -bis[di(5-methyl-2-furyl)phosphino]ferrocene ( 1 ) has been obtained from the bromophosphine BrP(Fu Me ) 2 and the dilithioferrocene/TMEDA adduct. The quantitative addition of this ferrocene derivative to the tetracarbonyl dimer [(CO) 4 Rh 2 {μ-(S t Bu) 2 }] leads, through decarbonylation, to the dinuclear rhodium complex [(CO) 2 Rh 2 {μ-(S t Bu) 2 }{μ- P , P -Fc[P(Fu Me ) 2 ] 2 }] ( 2 ) in high yield. A X-ray structure [ orthorhombic , space group P 2 1 2 1 2 1 ; a =11.2982(2) A, b =13.3165(3) A, c =27.2687(7) A] and the solution multinuclear NMR characterization are reported, which show that the rare “quasi-closed bridging” A-frame struc…
Recognition of Li+ by a Salophen−UO2 Homodimeric Complex
2009
Self-assembly via mutual U-coordination of the salophen-UO(2) complex 1 creates a dimeric species which is shown to be useful for metal binding. Indeed, the 1 dimer has affinity for alkali metal cations and, interestingly, a marked selectivity for Li(+), determined by electrospray ionization mass spectrometry and (1)H NMR techniques. X-ray diffraction helped in the elucidation of the dimeric complex structure, which presents a crown-ether-type coordination site, in analogy to the more familiar 12-crown-4, responsible for the metal interaction. Comparison with isomer 2, and the salen derivative 3, increases the understanding of the behavior of such systems in solution and in the solid state.
Synthesis and crystal structure of {Rh2(O2CCH3)4·P(o-CH3OH6H4)Ph2}2. A novel dirhodium(II) monoadduct with intermolecular μ-oxo interactions
1997
Abstract We have investigated the reaction of dirhodium tetraacetate with the phosphine P( o -CH 3 OH 6 H 4 )Ph 2 (P) under different experimental conditions. From these reactions we have been able to isolate the dirhodium tetraacetate phosphine mono-adduct. The crystal structure shows that in the solid state this compound forms a centrosymmetric dimer of the dimer, {Rh 2 (O 2 CCH 3 ) 4 ·P(0-CH 3 OC 6 H 4 )Ph 2 } 2 , in which we oxygen atom from one acetate group in one Rh 2 (O 2 CCH 3 ) 4 ·P unit is axially coordinating one Rh atom on another Rh 2 (O 2 CCH 3 ) 4 · P unit (Rh⋯) 2.347(3) A intermolecular versus Rh⋯O 2.455(3) A intermolecular), and vice versa. The RhRh bond distance is 2.414…