共查询到20条相似文献,搜索用时 437 毫秒
1.
Reaction of (NEt 4) 2MS 4 (M = Mo, W) with CuCl and KSCN (or NH 4SCN) in acetone or acetonitrile affords a new set of mixed metal–sulfur compounds: infinite anionic chains Cu 4(NCS) 5MS 43− (1,2), (CuNCS) 3WS 42− (3) and two dimensional polymeric dianions (CuNCS) 4MS 42− (4,5). Crystal of 1 (M = W) and 3 are triclinic, space group P1(1: a = 10.356(2), b = 15.039(1), c = 17.356(2)Å, = 78.27(1)°, β = 88.89(2)° and γ = 88.60(1)°, Z = 2, R = 0.04 for 3915 independent data;3: a = 8.449(2), b = 14.622(4), c = 15.809(8)Å, = 61.84(3)°, β = 73.67(3)° and γ = 78.23(2)°, Z = 2, R = 0.029 for 6585 independent data). Crystals of 4 (M = W) and 5 (M = Mo) are monoclinic, space group P2 1/ m, Z = 2 (4: a = 12.296(4), b = 14.794(4), c = 10.260(3)Åand β = 101.88(3)°, R = 0.034 for 4450 independent data;5: a = 12.306(2), b = 14.809(3), c = 10.257(2)Åand β = 101.99(3)°, R = 0.043 for 3078 independent data). The crystal structure determinations of 4 and 5 show that four edges of the tetrahedral MS 42− core are coordinated by copper atoms forming WS 4Cu 4 aggregates linked by eight-membered Cu(NCS) 2Cu rings. A two-dimensional network is thus formed in the diagonal (101) plane. The space between the anionic two-dimensional networks is filled with the NEt 4+ cations. Additional NCS groups lead to the [Cu 4(NCS) 5WS 4] 3− (1) trianion connected by NCS bridges forming pseudo-dimers. These latter are held together by weak CuS(NCS) interactions giving rise to infinite chains along a direction parallel to [100]. In contrast complex3 develops infinite chains from WS 4Cu 3 aggregates with the same Cu(NCS) 2Cu bridges as in 4 and 5. These chains are running along a direction parallel to [010]. The structural data of the different types of polymeric compounds containing MS 42− and CuNCS have been used to interpret vibrational spectroscopic data of the thiocyanate groups. 相似文献
2.
Cycloaddition of cyclopentadiene with a
-arabinose-derived cis-dienophile, methyl ( Z)-4,5,6,7-tetra- O-acetyl-2,32-dideoxy-
- arabino-hept-2-enonate (2), under thermal conditions gave essentially a single norbornene aduct, isolated crystaline in 81% yield and identified by NMR spectroscopy and X-ray crystallography as methyl (5R,6S)-6- endo-(1,2,3,4-tetra- O-acetyl-
- arabino-tetritol-1-yl) bicyclo[2.2.1]-hept-2-ene-5- endo-carboxylate (3). The diene adds exclusively from the si-face of the dienophile and give only the endo product. The same sequence starting from
-arabinose gave the enantiomer (7) of 3. In contrast, a related cis-dienophile (9) having a butenolide ring with cyclopentadiene from the opposite ( re) face giving mainly the endo adduct (5S,6R)-6- endo-(2,3,4-tri- O-acetyl)-
- arabino-tetritol-1-yl) bicyclo[2.2.1]hept-2-ene-5- endo-carboxylic acid 1,4-lactone (10), isolated crystalline in 70% yield, whose structure was again established by NMR spectroscopy, and firmly consolidated by X-ray crystallography. The minor (11%) product was the exo(5S,6R)isomer 11. A cis-enonate 14, analogous to 2 but deoxygenated at the allylic position, showed negligible diastereofacial selectivity ans reacted with cyclopentadiene to give a mixture of all four possible adducts. A 6-membered ring dienophile 16 was also subjected to the same cycloaddition for comparison with the butenolide 9; it gave principally the two endo products 17 and 19 in 31 and 38% yields, respectively, accompanied by 12% of a mixture of the two exo products (18 and 20). The quantitative distribution of cycloaddition products as a function of dienophile stereochemistry is discussed. The high degree of asymmetric induction observed, especially with the readily accesible dienophiles 2 and 7, providesa valuable route of access to enantiomerically pure tetra- C-substituted cycloalkanes. 相似文献
3.
The preparation and structural characterization of dirhodium(II) tetrakis[ N,N-dimethyl-2-pyrrolidone-5( S)-carb- oxamide], Rh 2(5 S-DMAP) 4, a new sterically-demanding catalyst for enantioselective metal carbene transformations, is described. The pyrrolidone ligands are arrayed around the dirhodium(II) core with two oxygen and two nitrogen donor atoms, each oriented cis, bound to each octahedral rhodium. The crystal structure of this compound has been determined to be that of Rh 2(5 S-DMAP) 4(CH 3CN) 2·CH 3CN·6H 2O: space group P2 12 12 1 with cell constants a= 12.685(4), b=15.050(3), c=24.035(4) Å; V=4588.5(1.9) Å 3, Z=4, R=0.0316, Rh---Rh DISTANCE =2 4538(5) Å. Decreased activity for diazodecomposition catalyzed by Rh 2(5 S-DMAP) 4 is observed, and enantiocontrol for cyclopropanation and carbon-hydrogen insertion is lower than expected by analogy to the corresponding di- rhodium(II) tetrakis[methyl 2-pyrrolidone-5( S)-carboxylate], Rh 2(5 S-MEPY) 4 Electronic stabilization of the in- termediate metal carbene is absent in reactions catalyzed by Rh 2(5 S-DMAP) 4. 相似文献
4.
The molecular structure of trans-[Pd(PhC(O)CHP(n-C 4H 9) 3) 2Cl 2] has been determined via a single crystal X-ray diffraction study: triclinic, P1, a = 8.876(2), b = 10.908(3), c = 11.938(4)Å, = 97.06(2)°, β = 102.79(2)°, γ = 100.51(2)°, V= 1092.1(5)Å 3, Z = 1 and R( F) = 4.61%. The phosphorus ylide molecules are bound to the palladium atom through their methine carbon atoms, the overall coordination geometry about the palladium being square planar. The protons in the ortho-positions of the two phenyl group are poised above and below the palladium atom, suggesting that the complex is a precursor of the ortho-metalated complex [Pd(μ-Cl)(C 6H 4C(O)CHP(n-C 4H 9) 3)] 2 synthesized earlier in our laboratory. 相似文献
5.
The reaction of [Re(NMe)Cl 3(PPh 3) 2] with the pentadentate [N 3S 2] ligand pyN 2H 2S 2---H 2 [2,6-bis(2-mercaptophenylamino)dimethylpyridine] (1) in the presence of triethylamine did not yield the anticipated six-coordinate complex [Re(NMe)(η 5-pyN 2HS 2)] (2), but rather resulted in cleavage of the Re(V)=NMe bond. A novel six-coordinate Re(IV) [N 3S]/[NS] complex [Re(η 4-SC 6H 4---2-NCH 2---C 5H 3N---C=NC 6H 4---2-S)(η 2-NHC 6H 4---2-S)] (4) was thus obtained with the simultaneous coordination of 2-aminothiophenol, a dianionic bidentate [NS] donor resulting from the decomposition of the parent ligand and ligand 3, a dianionic tetradentate [N 3S] donor formed by partial self-condensation and subsequent oxidation of the parent ligand 1. Crystal data for 4: C 25H 18N 4S 3Re·CH 2Cl 2, monoclinic, space group P2 1/ n, a=9.255(2) Å, b=11.181(2) Å, c=25.316(4) Å, β=97.434(3)°, V=2587.8(7) Å 3 and Z=4. 相似文献
6.
1. Succinate-cytochrome c reductase activity was reconstituted by incubating a mixture of succinate dehydrogenase, cytochrome c1, ubiquinone-10, phospholipid and a preparation of cytochrome b, made by the method of
. 2. Preparations of cytochrome b active in reconstitution contained 5–28% native cytochrome b, as adjudged by reducibility with succinate in the reconstituted preparation and by lack of reaction with CO. Preparations of cytochrome b containing no native cytochrome b according to this criterion were inactive in reconstitution. 3. With a fixed amount of cytochrome b, the activity of the reconstituted preparation increased with increasing amounts of cytochrome c1 until a ratio of about 2b (total): 1c1 (allowing for the cytochrome c1 present in the cytochrome b preparation) was reached. 4. The amount of antimycin necessary for maximal inhibition of the reconstituted enzyme is a function of the amount of the cytochrome b and is independent of the amount of cytochrome c1. It is equal to about one half the amount of native cytochrome b. 5. Preparations of intact or reconstituted succinate-cytochrome c reductase or of cytochrome b completely quench the fluorescence of added antimycin, until an amount of antimycin equal to onehalf the amount of native cytochrome b present was added. Antimycin added in excess of this amount fluoresces with normal intensity. The quenching is only partial in the presence of Na2S2O4. Denatured cytochrome b does not quench the fluorescence. 6. Since preparations of cytochrome b active in reconstitution contained cytochrome c1 in an amount exceeding one half the amount of native cytochrome b present in the preparation, there is no evidence that native cytochrome b has been resolved from cytochrome c1. The stimulatory action of cytochrome c1 may be due to the restoration of a damaged membrane conformation. 7. Based on the assumption that the bc1 segment of the respiratory chain contains 2b:1c1:1 antimycin-binding sites, the specific quenching of antimycin fluorescence by binding to cytochrome b enables an accurate determination of the absorbance coefficients of cytochromes b and c1. These are 25.6 and 20.1 mM−1×cm−1 for the wavelength pairs 563–577 nm and 553–539 nm, respectively, in the difference spectrum reduced minus oxidized. 相似文献
7.
Treatment of the A-ring aromatic steroids estrone 3-methyl ether and β-estradiol 3, 17-dimethyl ether with Mn(CO) 5+BF 4− in CH 2Cl 2 yields the corresponding [(steroid)Mn(CO) 3]BF 4 salts 1 and 2 as mixtures of and β isomers. The X-ray structure of [(estrone 3-methyl ether)Mn(CO) 3]BF 4 · CH 2Cl 2 (1) having the Mn(CO) 3 moiety on the side of the steroid is reported: space group P2 1 with a=10.3958(9), b=10.9020(6), c=12.6848(9) Å, β=111.857(6)°, Z=2, V=1334.3(2) Å 3, calc=.481 cm −3, R=0.0508, and wR=0.0635. The molecule has the traditional ‘piano stool’ structure with a planar arene ring and linear Mn---C---O linkages. The nucleophiles NaBH 4 and LiCH 2C(O)CMe 3 add to [(β-estradiol 3,17-dimethyl ether)Mn(CO) 3]BF 4 (2) in high yield to give the corresponding - and β-cyclohexadienyl manganese tricarbonyl complexes (3). The nucleophiles add meta to the arene -OMe substituent and exo to the metal. The and β isomers of 3 were separated by fractional crystallization and the X-ray structure of the β isomer with an exo-CH 2C(O)CMe 3 substituent is reported (complex 4): space group P2 12 12 1 with a=7.5154(8), b=15.160(2), c=25.230(3) Å, Z=4, V=2874.4(5) Å 3, calc=1.244 g cm −3, R=0.0529 and wR2=0.1176. The molecule 4 has a planar set of dienyl carbon atoms with the saturated C(1) carbon being 0.592 Å out of the plane away from the metal. The results suggest that the manganese-mediated functionalization of aromatic steroids is a viable synthetic procedure with a range of nucleophiles of varying strengths. 相似文献
8.
The crystal structures of Li[Fe(trtda)]·3H 2O and Na[Fe(eddda)]·5H 2O (trtda = trimethylenediaminetetraacetate and eddda = ethylenediamine- N,N′-diacetate- N,N′-di-3-propionate) have been determined by single crystal X-ray diffraction techniques. The former crystal was monoclinic with the space group P2 1/ n, a = 17.775(3), b = 10.261(1), c = 8.883(2)Å, β = 95.86(4)° and Z = 4. The latter was also monoclinic with the space group P2 1/ n, a = 6.894(2), b = 20.710(6), c = 13.966(3)Å, β = 101.44(2)° and Z = 4. Both complex anions were found to adopt an octahedral six-coordinated structure with all of six ligand atoms of trdta 4− or eddda 4− coordinated to the Fe(III) ion, unlike the corresponding edta 4− complex which is usually seven-coordinate with the seventh coordination site occupied by H 2O. Of the three geometrical isomers possible for the eddda complex, the trans(O 5) isomer was actually found in the latter crystal. Factors determining the structural types of metal–edta complexes are discussed in detail. 相似文献
9.
In this paper, we report the crystal and molecular structure of μ-oxo-bis(5,10,15,20)tetrakispentafluorophenyl)porphinatoiron(III) [(TPP(F 5)Fe) 2O]. The crystals belong to the tetragonal system, space group I4 1/ a, with a = b = 26.362(7), c = 30.886(8)Å, V = 21465Å 3, Z = 8 and Dcalc = 1.496. Discrepancy indices are R1 = 0.084 and R2 = 0.104 for 3320 reflections having I3σ( I). The FeN p average distance, 2.088(11)Å, is at the long end of the range of high-spin ferric porphyrin while the FeO distances (1.775(1)Å) are similar to those of the non-halogenated analog (TPPFe) 2O. The FeOFe angle of 178.4(5)° shows an essentially linear oxo bridge. The 0.673(2)Ådisplacement of the iron atom from the porphyrin mean plane is unusually large. The facing porphyrin rings are twisted 47° with respect of each other giving the molecule nearly exact D4d symmetry. 相似文献
10.
Tricarbonyl(η 6-1-oxobenzocyclobutene)chromium(0) (1) can be transformed to tricarbonyl(η 6-1- endo-hydroxybenzocyclobutene) chromium(0) derivatives with substituents R (R=CH 3, CH=CH 2, (CH 2) 4CH=CH 2, (CH 2) 4OSi(Me) 2tBu) at Cl on the exo face of the complex. The relative configuration is proven by an X-ray crystal structure analysis of the trimethylsilyl ether 8 (C 16H 18CrO 4Si: a=8.693(1), b=9.490(1), c=11.063(1) Å, =97.51(1), β=110.32(1), γ=95.38(1)°, triclinic, space group P
(No.2), R=0.037, Rw=0.052 for 4609 observed reflections. Attempts directed at an intramolecular cycloaddition of the ortho-quinodimethane complex derived from 17 by anion promoted ring opening unexpectedly resulted in the formation of 12 as the product of an opening of the proximal bond of the anellated ring located between the hydroxy group and the coordinated aromatic ring in 16. The fact that the intermolecular cycloaddition reaction for 16 is possible in the presence of a dienophile is taken as evidence for an equilibrium between the alcoholate 17 and the two ring opened products 16 and 18. The proximal ring opening of 6 is not observed when the free organic ligand 21 is used as the educt. Ketone complexes 1 and 25 undergo proximal ring opening reaction when treated with alcoholate or primary amines. 相似文献
11.
1. 1. Three b-type cytochromes (b557.5, b560, and b562.5), plus a chromophore with an absorption peak at 558 nm at 77 °K, have been found to be associated with the electron transport system of bovine heart mitochondria. The reduced minus oxidized spectra of these components at 77 °K, as well as that of cytochrome c1, have been recorded with a wavelength accuracy of ± 0.1 nm and presented to the nearest 0.5 nm. All the major and β absorption peaks of cytochromes b557.5, b560, b562.5, c1 and c have been shown by fourth derivative analysis to be present in the dithionite-reduced minus oxidized spectra of mitochondria and submitochondrial particles. 2. 2. The distribution of the above components has been studied in the four electron transfer complexes of the respiratory chain. Cytochromes b560, b562.5 and c1, as well as chromophore-558, were found to fractionate into Complex III (reduced ubiquinone-cytochrome c reductase), whereas cytochrome b557.5 was found in Complex II (succinate-ubiquinone reductase). 3. 3. Cytochrome b560 was readily reduced by NADH or succinate, but b562.5 was not reduced by substrates unless the preparation was treated with antimycin A. In antimycin-treated preparations pre-reduction of c1 with ascorbate inhibited the subsequent reduction of b562.5 by substrates. These results indicate that b560 and b562.5 correspond, respectively, to bK and bT previously described by Chance et al.14 (1970, Proc. Natl. Acad. Sci. U.S. 66, 1175–1182). 4. 4. Similar to b560, chromophore-558 can be reduced by substrates in the absence or presence of antimycin A. However, in antimycin-treated preparations, pre-reduction of c1 inhibits its subsequent reduction by substrates. This property is similar to that of b562.5. 5. 5. Cytochrome b557.5, which occurs in Complex II, appears to have a low mid-point potential. It can be reduced with dithionite and oxidized by fumarate or ubiquinone. CO treatment of dithionite-reduced b557.5 neither modified the spectrum of this cytochrome nor diminished the extent of b557.5 reoxidation by fumarate. 6. 6. Antimycin A treatment does not appear to alter the spectra of the above cytochromes. However, small amounts (< 4%) of ethanol or methanol, which are usually added to particles as solvent for antimycin A, have a pronounced effect on the peaks of cytochrome c1. The spectrum of cytochrome c1 at 77 °K as modified by 3% (v/v) ethanol is shown.
Abbreviations: ETP, non-phosphorylating electron transport particle preparation; ETPH, phosphorylating electron transport particle preparation; TMPD, tetramethylphenylenediamine; Complexes I, preparations of NADH-ubiquinone reductase; Complexes II, succinate-ubiquinone reductase; Complexes III, reduced ubiquinone-cytochrome c reductase; Complexes I-III, NADH-cytochrome c reductase; Complexes II-III, succinate-cytochrome c reductase 相似文献
12.
Complexes of type A 4[VO(tart)] 2· nH 2O, where A = Rb or Cs and tart = d, l-tartrate(4−) ( n = 2) or d,d-tartrate(4−) ( n = 2 for Rb and n = 3 for Cs), were prepared from an aqueous mixture of V 2O 5, AOH and H 4tart. These complexes were studied by single-crystal X-ray diffraction methods: Rb 4[VO( d, l-tart)] 2·2H 2O, space group P1 with a = 8.156(1), b = 8.246(1), c = 8.719(1)Å, = 66.09(1)°, β = 65.07(1)°, γ = 82.40(1)°, Z = 2, 1917 observed reflections, and final Rw = 0.035; Cs 4[VO( d, l-tart)] 2·2H 2O, space group P21/ c with a = 9.350(1), b = 13.728(2), c = 8.479(1)Å, β = 106.77(1)°, Z = 4, 2235 observed reflections, and final Rw = 0.054; Rb 4[VO( d, d-tart)] 2·2H 2O, space group P4122 with a = 8.072(1), c = 32.006(3)Å, Z = 8, 1014 observed reflections and final Rw = 0.038; Cs 4[VO( d, d-tart)] 2·3H 2O, space group P122 with a = 8.184(1), c = 33.680(5)Å, Z = 8, 1310 observed reflections, and final Rw = 0.063. Bulk magnetic susceptibility data (1.5–300 K) for these compounds and A 4[VO l, l-tart)] 2· nH 2O (A = Rb, Cs) were obtained on polycrystalline samples. These data were analyzed in terms of a Van Vleck exchange coupled S = 1/2 model which was modified to include an interdimer exchange parameters Θ. Analysis of the low-temperature (1.5–20 K) susceptibility data gave 2 J = +1.30 cm −1 and Θ = −1.86 K for Rb 4[VO( d, l-tart)] 2·2H 2O, 2 J = +1.16 cm −1 and Θ = −1.69 K for Cs 4[VO( d, l-tart)] 2·2H 2O, 2 J = +1.90 cm −1 and Θ = −0.82 K for Rb 4[VO( d, d-tart)] 2·2H 2O, 2 J = +2.04 cm −1 and Θ = −0.80 K for Rb 4[VO( l, l-tart)] 2·2H 2O, 2 J = +1.52 cm −1 and Θ = −0.25 K for Cs 4[VO( d, d-tart)] 2·3H 2O, and 2 J = +1.64 cm −1 and Θ = −0.31 K for Cs 4[VO( l, l-tart)] 2·3H 2O. These results suggest the magnitudes of intradimer (ferromagnetic and interdimer (antiferromagnetic) exchange interactions are similar in these complexes, as observed for the analogous Na salts. 相似文献
13.
Cobalt(III) complexes with a thiolate or thioether ligand, t-[Co(mp)(tren)] + (2), t-[Co(mtp)(tren)] 2+ (1Me) and t-[Co(mta)(tren)] 2+ (2Me), (mp = 3-mercaptopropionate, MA = 3-(methylthio)propionate and MTA = 2-(methylthio)acetate) have been prepared in aqueous solutions. The crystal structures of 1, 2, 1Me and 2Me were determined by X-ray diffraction methods. The crystal data are as follows, t-[Co(mp)(tren)]ClO 4 (1CIO 4): monoclinic, P2 1/ n, A = 10.877(8), B = 11.570(4), c = 12.173(7) Å, β = 92.20(5)°, V = 1531(1) Å 3, Z = 4 and R = 0.060; t-[Co(ma)(tren)]Cl·3H 2O (2Cl·3H 2O): monoclinic, P2 1/ n, a = 7.7688(8), B = 27.128(2), C = 7.858(1) Å, β = 100.63(1)°, V = 1627.7(3) Å 3, Z = 4 and R = 0.066; (+) 465CD- t-[ Co( mtp)( tren)]( ClO4) 2 ((+) 465CD-1Me(ClO 4) 2): orthorhombic, P2 12 12 1, A = 10.6610(7), B = 11.746(1), C = 15.555(1) Å, V = 1947.9(3) Å 3, Z = 4 and R = 0.068; (+) 465CD- t-[Co(mta)(tren)](ClO 4) 2 ((+) 465CD-2Me(ClO 4) 2): orthorhombic, P2 12 12 1, a = 10.564(1), B = 11.375(1), C = 15.434(2) Å, V = 1854.7(4) Å 3, Z = 4 and R = 0.047. All central Co(III) atoms have approximately octahedral geometry, coordinated by four N, one O, and one S atoms. All of the complexes are only isomer, of which the sulfur atom in the didentate-O,S ligands are located at the trans position to the tertiary amine nitrogen atom of tren. 1 and 1Me contain six-membered chelate ring, and 2 and 2Me do five-membered chelate ring in the didentate ligand. The chirality of the asymmetric sulfur donor atom in (+) 465CD-1Me is the S configuration and that in (+) 465CD-2Me is the R one. The 1H NMR, 13C NMR and electronic absorption spectral behaviors and electrochemical properties of the present complexes are discussed in relation to their stereochemistries. 相似文献
14.
The synthesis of the tetradentate pendant arm macrocycles 1,4,7-triazacyclononane- N-acetate (L 1) and N-(2-hydroxybenzyl)-1,4,7-triazacyclononane (HL 2) and their coordination chemistry with vanadium(IV) and (V) are reported. The following mononuclear species have been prepared and characterized by UV-Vis, IR spectroscopy: [L 1V IVO(NCS)] (1), [L 1VO 2]·H 2O (2), [L 2VO(NCS)] (3), [L 2VO(NCS)]Cl (4), and [L 2VO 2] (5). In addition, the dinuclear, mixed valent complexes [L 21V 2O 3]Br (6), [L 22V 2O 3](ClO 4)·0.5acetone (7), and the homovalent complex [L 22V 2O 3](ClO 4) 2 (8) have been synthesized. Complexes 2, 3, 6 and 7 have been characterized by single crystal X-ray crystallography. Crystal data: 2, space group P2 1c, a=9.944(4), b=6.701(3), c=18.207(8)Å, β=102.88(3)°, V=1182.7 Å 3, Z=4, Dcalc=1.51 g cm −3, R=0.049 based on 4760 reflections; 3, space group Pbca, A=11.003(6), b=14.295(7), C=20.21(1) Å, V=3178.8 Å 3, Z=8, Dcalc=1,50 g cm −3, R=0.057 based on 1049 reflections; 6, space Pbcn, a=12.922(3), B=13.852(3), C=12.739(3) Å, V=2280.3 Å 3, Z=4, Dcalc=1,75 g cm −3, R=0.047 based on 1172 reflections; 7, space group C2/ c, A=23.553(9), B=13.497(5), C=20.951(8) Å, β=90.03(3)°, V=6660.2 Å 3, Z=8, Dcalc=1.49 g cm −3, R=0.053 based on 3698 reflections. Complexes 6 and 7 are mixed valent V(IV)/(V) complexes containing the [OV---O---VO] 3+ core. In the solid state 6 belongs to class III (delocalized) and 7 to class I (localized) according to the Robin and Day classification of mixed valent compounds. A rationale for these differing electronic structures is given. 相似文献
15.
Chicken liver basic fatty acid-binding protein (p I = 9.0) has been purified with a high yield by a modification of a method originally applied to rat liver. The final product is highly homogeneous and can be used to grow crystals that belong to two different space groups. The crystals are either tetragonal, space group P4 22 12 with a = b = 60.2 Å and c = 138.1 Å or orthorhombic, space group P2 12 12 1 with a = 60.7 Å, b = 40.1 Å and c = 66.7 Å. The second form appears to be more suitable for X-ray diffraction studies, it diffracts to at least 2.8 Å resolution and it is believed to contain one protein molecule in the crystallographic asymmetric unit. 相似文献
16.
Two novel, weakly antiferromagnetically coupled, tetranuclear copper(II) complexes [Cu 4(PAP) 2(μ 2-1,1-N 3) 2(μ 2-1,3-N 3) 2(μ 2-CH 3OH) 2(N 3) 4 (1) (PAP = 1,4-bis-(2′-pyridylamino)phthalazine) and [Cu 4(PAP3Me) 2 (μ 2-1,1-N 3) 2(μ 2-1,3-N 3) 2(H 2O) 2(NO 2) 2]- (NO 3) 2 (2) (PAP3Me = 1,4-bis-(3′-methyl-2′-pyridyl)aminophthalazine) contain a unique structural with two μ 2-1,1-azide intramolecular bridges, and two μ 2-1,3-azide intermolecular bridges linking pairs of copper(II) centers. Four terminal azide groups complete the five-coordinate structures in 1, while two terminal waters and two nitrates complete the coordination spheres in 2. The dinuclear complexes [Cu 2(PPD)(μ 2-1,1-N 3)(N 3) 2(CF 3SO 3)]CH 3OH) (3) and [Cu 2(PPD)(μ 2-1,1-N 3)(N 3) 2(H 2O)(ClO 4)] (4) (PPD = 3,6-bis-(1′-pyrazolyl)pyridazine) contain pairs of copper centers with intramolecular μ 2-1,1-azid and pyridazine bridges, and exhibit strong antiferromagnetic coupling. A one-dimensional chain structure in 3 occurs through intermolecular μ 2-1,1-azide bridging interactions. Intramolecular Cu-N 3-Cu bridge angles in 1 and 2 are small (107.9 and 109.4°, respectively), but very large in 3 and 4 (122.5 and 123.2°, respectively), in keeping with the magnetic properties. 2 crystallizes in the monoclinic system, space group C2/ c with a = 26.71(1), b = 13.51(3), c = 16.84(1) Å, β = 117.35(3)° and R = 0.070, Rw = 0.050. 3 crystallizes in the monoclinic system, space group P2 1/ c with a = 8.42(1), b = 20.808(9), c = 12.615(4) Å, β = 102.95(5)° and R = 0.045, Rw = 0.039. 4crystallizes in the triclinic system, space group P1, with a = 10.253(3), b = 12.338(5), c = 8.072(4) Å, = 100.65(4), β = 101.93(3), γ = 87.82(3)° and R = 0.038, Rw = 0.036 . The magnetic properties of 1 and 2 indicate the presence of weak net antiferromagnetic exchange, as indicated by the presence of a low temperature maximum in χ m (80 K (1), 65 K (2)), but the data do not fit the Bleaney-Bowers equation unless the exchange integral is treated as a temperature dependent term. A similar situation has been observed for other related compounds, and various approaches to the problem will be discussed. Magnetically 3 and 4 are well described by the Bleaney-Bowers equation, exhibiting very strong antiferromagnetic exchange (− 2 J = 768(24) cm −1 (3); − 2 J = 829(11) cm −1 (4)). 相似文献
17.
Crystals of ribosomal protein L6 from Bacillus stearothermophilus suitable for high resolution structural studies have been obtained. Crystals are hexagonal with space group P6 122 (or the enantiomorph P6 522) and cell dimensions a = b = 72.7 Å, c = 124.9 Å. A search for heavy atom derivatives is in progress. 相似文献
18.
Compounds of formula [Al(CH 3CN) 6][MCl 6] 3(CH 3CN) 3 (M=Ta (1); Nb (2); Sb (3)) have been synthesized from the reactions of MCl 5 and AlCl 3 in acetonitrile and characterized by X-ray crystallography. Complex 1 crystallizes in the tetragonal space group P4/ mbm with a = B = 10.408(2), C = 7.670(3) Å, V = 830.9(4) Å 3 and Z = 2/3. Complex 2 crystallizes in the tetragonal space group P4/mnc with a = B = 330( a), C = 15.320(3) Å 3 V = 1634.8(4) Å 3 and Z = 4/3. Complex 3 also crystallizes in the tetragonal space group P4/ mnc with a = B = 10.313(1), C = 15.238(2) Å, V = 1621.0(1) Å 3 and Z = 4/3. The non-integer Z values for complexes 1–3 result unusual problems of disorder and/or twinning in these crystal structures due to their high symmetry. The M---Cl distances range from 2.329(3) Å in the Ta complex to 2.355(1) Å in the Sb complex, while the Al---N distances are similar in all three complexes, ranging from 1.92(1) to 1.97(1) Å, respectively. Complexes 1–3 are the first structurally characterized complexes that contain a (hexaacetonitrile)aluminum(III) cation. 相似文献
19.
Based on the new ligand bis(1-methyl-2-benzimidazolyl) propane (abbreviated as mtbz) several new copper(II) coordination compounds have been prepared and characterized structurally and spectroscopically. Two representative compounds, i.e. [Cu 2(mtbz) 2(CH 3) 2- (CF 3SO 3)](CF 3SO 3) (1) and [Cu 2(mtbz) 2(CH 3O) 2](ClO 4) 2 (4) were characterized structurally by X-ray diffraction. Crystal data for 1: monoclinic, space group P2 1/ c, a=13.6585(5), B=39.981(3), C=20.919(1) Å, β=125.98(1)°, Z=8. Crystal data for 4: monoclinic, space group P2 1/ c, a=13.115(2), B=9.523(2), C=17.908(4) Å, β=111.71(1)°, Z=2. Structures 1 and 4 each consist of a dinuclear unit with bridging methoxo groups and one ligand linked to each copper via an N atom. Structure 1 (which consists of two dinuclear, crystallographically independent, but chemically identical units) has the two copper atoms bridged by a triflate anion, providing each copper atom a square-pyramidal coordination, while the copper atoms in structure 4 have an almost a square-planar geometry. The Cu---Cu distances (Å) within the dinuclear units are: 1, 2.9775(13), 2.9751(13); 4, 2.9872(16); the Cu---O---Cu bridging angles (°) are: 1, 101.7(3), 101.7(3), 100.9(3), 102.1(3); 4, 103.2(2). The mid-IR section focused on the vibrations of the triflate anion reveals interesting results concerning the assignments of that anion related to the vas(S---O) band. Characteristic Cu---O vibrations in the far-IR section were found at 386 and 230 cm −1 for the methoxo-bridged and 454 and 332 cm −1 for the ethoxo-bridged compounds. These dinuclear species are EPR silent, and only a weak signal of monomeric impurities is observed. They also show a diamagnetic behavior below room temperature. 相似文献
20.
The molecular and crystal structure of
- glycero-
- allo-heptitol has been determined. It crystallises in the orthorhombic space-group P2 12 12 with a = 8.399(2), b = 23.484(8), c = 4.664(2) Å, = β = γ = 90°, and Z = 4. The heptitol was found to be in the 3G− form, which has a 1,3-parallel interaction between C-2 and O-5. In solution, as determined by 1H-n.m.r. spectroscopy, the heptitol and its hepta-acetate also assume conformations which have a C,O parallel interaction. Such an interaction has also been found to occur in several other heptitols and in hexose dialkyl acetals. Because conformers with such an interaction had been disregarded in the past, the conformations of several heptitols had been wrongly assigned. 相似文献
|