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131.
132.
The pyrazole derivatives of aminoethane N,N-bis(3,5-dimethyl-1-pyrazolyl- methyl)aminoethane (aebd) and N,N-bis(1-pyrazolylmethyl)aminoethane (aebp) form co- ordination compounds with copper(I) of stoichiometry [Cu(L)X], with X = Cl, Br, I and SCN, and [Cu(L)2X], with X = CF3SO3 and BF4. The ligands chelate in a bidentate manner, with only the pyrazole groups coordinating. The crystal structures of two representative examples have been determined: [Cu(aebp)Cl]2 is triclinic, space group P
, with a = 8.711(2), b = 9.351(1) and c = 9.528(1) Å, = 68.57(1)°, β = 61.47(1)° and γ = 77.82(1)°, and Z = 2. Standard least-squares refinement gave R = 0.029 (Rw = 0.038) for 1804 reflections. [Cu(aebp)2]CF3SO3 is monoclinic, space group P21/n, with a = 13.352(5), b = 14.663(3) and c = 15.752(4) Å, β = 117.49(3)°, and Z = 4. Standard least-squares refinement gave R = 0.029 (Rw = 0.032) for 1786 reflections. In both cases the copper environment is slightly-distorted tetrahedral. The chloride compound is dimeric with one ligand molecule (Cu---N distances of 2.011(2) and 2.047(2) Å) and two bridging chlorides per copper (Cu---Cl distances of 2.3874(8) and 2.4094(8) Å). With the non- coordinating triflate anion, a monomeric compound with two ligand molecules per copper was obtained (Cu---N distances of 2.018(4), 2.028(4), 2.049(4) and 2.050(4) Å). 相似文献
133.
Deuteration of Zr2Cu leads to a reconstruction of its MoSi2-type metal atom arrangement. While the tetragonal alloy contains isolated copper atoms (Cu-Cu = 3.22 angstroms) in a cubic zirconium atom environment, the monoclinic deuteride Zr2CuD4.71 contains Cu2 dumbbells (Cu-Cu = 2.39 angstroms), of which each copper atom has a trigonal-prismatic zirconium atom environment. Deuterium occupies five sites, of which four have tetrahedral metal configurations (two Zr4-type and two Zr3Cu-type) and are fully occupied while one has a trigonal-bipyramidal metal configuration (Zr3Cu2-type) and is partially occupied (71%). Copper is bonded to four deuterium atoms in a saddle-like configuration (Cu-D = 1.73-1.87 angstroms). Two of the ligands connect copper in a nearly linear Cu-D-Cu arrangement to partially interrupted dimeric [Cu2D6](n)() ribbons running perpendicular to the Cu2 dumbbell direction. At the upper phase limit, the ribbons are presumably no longer interrupted and the deuteride can be described by the limiting ionic formula 2Zr2+[Cu(+)D3](2-)2D-. 相似文献
134.
Peptide retention in reversed-phase chromatography depends mainly on the amino acid composition of peptides and can therefore be predicted by summing the relative hydrophobic contributions of each constitutive amino acid residue. The prediction is correct for small peptides but overestimates the retention times of peptides larger than 10-15 residues. A new prediction model is proposed in which the contribution to peptide retention of each amino acid residue is not a constant but a decreasing function of peptide length. From the retention times of 104 peptides, the parameters of decreasing functions were estimated by a non-linear multiple regression analysis. The contribution to peptide retention of charged, polar and non-polar residues appears to be differently affected by peptide length. The secondary structure of most peptides during reversed-phase high-performance liquid chromatography could be responsible for this. The high correlation between the predicted and observed retention times of peptides which were not used to establish the model indicates a good predictive accuracy of the new model. 相似文献
135.
Organotin enolates and α-organotin substituted nitriles or esters which are generally easy to obtain, can be used to alkylate α to functional groups.In the case of organotin enolates, heating with alkylating agents, usually gives monoalkylated products in very good yields: numerous examples with ketones and aldehydes are described.With α-organotin substituted nitriles and esters, direct alkylation does not occur, but good results can be obtained in the presence of either magnesium or lithium bromide, or after a metal exchange reaction with a Grignard or lithium reagent. 相似文献
136.
137.
The title compounds and their deuterides have been prepared by solid-state and solid-gas reactions from the elements and investigated by X-ray and neutron powder diffraction as a function of temperature. At room temperature they crystallize with an anion-deficient cubic K2PtCl6-type structure (space group ) in which five hydrogen (deuterium) atoms surround iridium randomly on six octahedral sites with average bond distances of Ir-D=169-171 pm. At low temperature they undergo a tetragonal deformation (space group I4/mmm) to the partially ordered Sr2IrD5 (T=4.2K)-type structure in which four hydrogen (deuterium) atoms occupy planar sites with full occupancy (Ir-D=166-170 pm) and two hydrogen (deuterium) atoms axial sites (Ir-D=174-181 pm) with ∼50% occupancy, i.e., the data are consistent with a mixture of square-pyramidal [IrD5]4− complexes pointing in two opposite directions. The transitions occur at ∼240 K (Eu0.5Ca1.5IrD5, Eu0.5Sr1.5IrD5), ∼210 K (EuSrIrD5), ∼200 K (EuCaIrD5, Eu2IrD5), and are presumably of first order. 相似文献
138.
The deuterated C15-type Laves phase ZrV2D3.6 undergoes a structural phase transition near room temperature (T ≈ 325 K). In the cubic high-temperature phase the deuterium atoms are disordered over two types of tetrahedral interstices, the centres of which are 1.3 Å apart. In the tetragonal low-temperature phase the D atoms are ordered and occupy only the energetically more favourable interstices. The tetragonal structure is isotypic with the low-temperature phase of HfV2D4. The shortest D—D distance is 2.1 Å. 相似文献
139.
Superconducting Mo3S4(Tc=1.8 K) was prepared from the ternary sulfides MMo3S4 (M=Cu, Ni) by the acid extraction method, and was studied by neutron diffraction and NMR spectroscopy. In contrast to earlier reports no significant amounts of hydrogen could be found in the rhombohedral structure. However, large proton concentrations were found in samples which had been exposed to moist air. 相似文献
140.