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1.
We analyzed chemical bonding in low-lying isomers of the recently computationally predicted B(6)H(6)Li(6) molecule. According to our calculations the benzene-like B(6)H(6)Li(6) (D(2h), (1)A(1g)) arachno structure with the planar aromatic B(6)H(6)(6-) anion is the most stable one. A nido isomer with two aromatic B(6)H(6)(4-) (pentagonal pyramid) and Li(3)(+) (triangular) moieties, which can be considered as derived from the global minimum structure through a two-electron intramolecular transfer from B(6)H(6)(6-) to three Li(+) cations, was found to be 10.7 kcal/mol higher in energy. A closo isomer with three aromatic moieties (octahedral B(6)H(6)(2-) and two Li(3)(+)) was found to be 31.3 kcal/mol higher in energy than the global minimum. Another isomer with three aromatic moieties (two B(3)H(3)(2-) and Li(3)(+)) was found to be substantially higher in energy (74.4 kcal/mol). Thus, the intramolecular electron transfers from the highly charged B(6)H(6)(6-) anion to cations are not favorable for the B(6)H(6)Li(6) molecule, even when a formation of three-dimensional aromatic B(6)H(6)(2-) anion and two sigma-aromatic Li(3)(+) cations occurs in the closo isomer.  相似文献   

2.
Rate constants were measured for electron attachment to MoF(6), ReF(6), and WF(6) in 133 Pa of helium gas using a flowing-afterglow Langmuir-probe apparatus. The experiment is a thorny one because the molecules tend to form oxide impurities on feedline surfaces and because of thermal decomposition of MoF(6) on surfaces as the gas temperature is increased. The electron attachment rate constant for MoF(6) is (2.3+/-0.8)x10(-9) cm(3) s(-1) at 297 K; only MoF(6) (-) is formed in the temperature range of 297-385 K. The rate constant increases with temperature up to the point where decomposition becomes apparent. Electron attachment to ReF(6) occurs with a rate constant of (2.4+/-0.8)x10(-9) cm(3) s(-1) at 297 K; only ReF(6) (-) is produced. MoF(6) (-) reacts with ReF(6) to form ReF(6) (-) on essentially every collision, showing definitively that the electron affinity of ReF(6) is greater than that of MoF(6). A rate constant of (5.0+/-1.3)x10(-10) cm(3) s(-1) was measured for this ion-molecule reaction at 304 K. The reverse reaction is not observed. The reaction of Ar(+) with MoF(6) was found to produce MoF(5) (+)+F, with a rate constant of (1.8+/-0.5)x10(-9) cm(3) s(-1). WF(6) attaches electrons so slowly at room temperature that the attachment rate was below detection level (< or =10(-12) cm(3) s(-1)). By 552 K, the attachment rate constant reaches a value of (2+/-1)x10(-10) cm(3) s(-1).  相似文献   

3.
The Cs3Mo6Ii6Ii2-xSeixIa6 series has been obtained by a solid-state route. There is evidence for a solid solution between the compositions Cs3Mo6Ii6Ii0.8Sei1.2Ia6 and Cs3Mo6Ii6Ii0.4Sei1.6Ia6 (space group: R3c, Z=6; a=16.7065(4), c=20.5523(4) A, V=4967.8(2) A3 and a=16.6354(3), c=20.5444(4) A, V=4923.7(2) A3, respectively). The structure of this new series is based on magnetic [Mo6Ii6Sei2Ia6]3- and diamagnetic [Mo6Ii7SeiIa6]3- units with 23 and 24 valence electrons per Mo6 cluster, respectively. For a particular x, the structure of Cs3Mo6Ii6Ii2-xSexIa6 is based on a mixture of (x-1) [Mo6Ii6Sei2Ia6]3- with (2-x) [Mo6Ii7SeiIa6]3-. This leads to an average [Mo6Ii6Ii2-xSexIa6]3- ionic unit deduced from single-crystal X-ray diffraction investigations. The two inner positions of the average face-capped [Mo6Ii8-xSeixIa6]3- ionic units (located on the threefold axis of the unit) are randomly occupied by iodine and selenium, whereas the other ligand positions are fully occupied by iodine. Low-temperature electron paramagnetic resonance (EPR) studies reveal a signal split into two components with g||>gperpendicular. The reciprocal double integration intensity of the EPR signal versus T graph reveals a typical Curie law behavior. A density functional theory (DFT) study indicates that occupation of the inner position on the threefold axis by selenium atoms is preferred energetically among the three possible distributions of selenium atoms. The comparison of experimental and theoretical g values confirms the crystallographic analysis and agrees with the axial elongation of the Mo6 cluster within the crystal structure.  相似文献   

4.
5.
《Tetrahedron: Asymmetry》1999,10(16):3189-3196
Optically active 3-alkoxy-6-hydroxymethyl-6-methyl-2-cyclohexenone and 6-acetoxymethyl-3-alkoxy-6-methyl-2-cyclohexenone were efficiently obtained by lipase-catalyzed kinetic resolution. (R)-6-Acetoxymethyl-3-(methoxymethoxy)-6-methyl-2-cyclohexenone was converted to the synthetic intermediate of cassiol.  相似文献   

6.
4-(3-Alkylureido)-2, 2, 6, 6-tetramethylpiperidine-1-oxyls are rapidly oxidized by N2O4 or NOCl to 4-(3-alkylureido)-2, 2, 6, 6-tetramethyl-1-oxopiperidinium nitrates and chlorides, which are then nitrosated to 4-(3-alkyl-3-nitrosoureido)-2, 2, 6, 6-tetramethyl-1-oxopiperidinium salts. The perchlorates of the latter were prepared by an exchange reaction with HClO4. The nitrosation of alkylureidooxoammonium salts is the first example of chemical modification of oxoammonium derivatives in which the highly reactive >N+=O group is inert toward the reagent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 542–547, March, 1993.  相似文献   

7.
The first face-capped octahedral clusters with 25 metal-based valence electrons are shown to provide versatile building units capable of engaging in magnetic exchange coupling. Reactions of [Re(5)OsSe(8)Cl(6)](3-) and [Re(4)Os(2)Se(8)Cl(6)](2-) with NaCN in a melt of NaNO(3) or KCF(3)SO(3) afford the 24-electron clusters [Re(5)OsSe(8)(CN)(6)](3-) and [Re(4)Os(2)Se(8)(CN)(6)](2-). The 13C NMR spectrum of a 13C-labeled version of the latter species indicates a 1:2 mixture of cis and trans isomers. Cyclic voltammograms of the clusters in acetonitrile display reversible [Re(5)OsSe(8)(CN)(6)](3-/4-), cis-[Re(4)Os(2)Se(8)(CN)(6)](2-/3-), and trans-[Re(4)Os(2)Se(8)(CN)(6)](2-/3-) couples at E(1/2) = -1.843, -0.760, and -1.031 V vs FeCp(2)(0/+), respectively, in addition to other redox processes. Accordingly, reduction of [Re(5)OsSe(8)(CN)(6)](3-) with sodium amalgam and [Re(4)Os(2)Se(8)(CN)(6)](2-) with cobaltocene produces the 25-electron clusters [Re(5)OsSe(8)(CN)(6)](4-) and [Re(4)Os(2)Se(8)(CN)(6)](3-). EPR spectra of these S = 1/2 species in frozen DMF solutions exhibit isotropic signals with g = 1.46 for the monoosmium cluster and g = 1.74 and 1.09 for the respective cis and trans isomers of the diosmium cluster. In each case, results from DFT calculations show the unpaired spin to delocalize to some extent into the pi* orbitals of the cyanide ligands, suggesting the possibility of magnetic superexchange. Reaction of [Re(5)OsSe(8)(CN)(6)](3-) with [Ni(H(2)O)(6)](2+) in aqueous solution generates the porous Prussian blue analogue Ni(3)[Re(5)OsSe(8)(CN)(6)](2).32H(2)O; however, the tendency of the 25-electron clusters to oxidize in water prohibits their use in reactions of this type. Instead, a series of cyano-bridged assemblies, [Re(6-n)Os(n)Se(8)[CNCu(Me(6)tren)](6)](9+) (n = 0, 1, 2; Me(6)tren = tris(2-(dimethylamino)ethyl)amine), were synthesized to permit comparison of the exchange coupling abilities of clusters with 23-25 electrons. As expected, the results of magnetic susceptibility measurements show no evidence for exchange coupling in the assemblies containing the 23- and 24-electron clusters, but reveal the presence of weak ferromagnetic coupling in [Re(4)Os(2)Se(8)[CNCu(Me(6)tren)](6)](9+). Assuming all cluster-Cu(II) exchange interactions to be equivalent, the data were fit to give an estimated coupling strength of J = 0.4 cm(-1). To our knowledge, the ability of such clusters to participate in magnetic exchange coupling has never previously been demonstrated.  相似文献   

8.
<正> Guanidinium bis (o - aminophenylarsenic) hexamolybdate belongs to monoclinic space group P21/c,with a=10. 217(2),b= 18. 870(2),c= 10. 939(2)A,β = 102. 82(3)°,Z = 2,V=2056. 4A3,and Dc=2. 477 g·cm-3. Each molecule contains one [(o-NH2C6H4As)2Mo6O24]4- anion and four CN3H6+ cations. In the anion,six distorted MoO6 octahedra are connected with edges-sharing to form a six-membered Mo ring which is capped above and below by two o - aminophenylarsenic groups. There is half a molecule in an asymmetric unit. It is interesting that both phenyl planes are almost perpendicular to the plane of the Mo atoms. The structure of the anion is similar to that of [ (CH3 As)2Mo6O24]4-,[(n-C3H7As)2Mo6O24]4- or [(C6H5CH2As)2Mo6O24]4-. This is the first example of this type of compounds in which the As atom is directly connected to a substituted phenyl group.  相似文献   

9.
The Vilsmeier reaction of nickel(II) chlorin P6 trimethyl ester with 3-dimethyl-aminoacrolein yielded nickel(II) chlorin P6 20-(2-formylvinyl) trimethyl ester and nickel(II) chlorin P6 3-(1-hydroxyethyl)-3-devinyl-20-(2-formylvinyl) trimethyl ester. Also, the outgrowths of nickel(II) chlorin P6 20-(2-formyl) trimethyl ester and nickel(II) chlorin P6 3-(2-formylvinyl)-3-devinyl-20-(2-formyl) trimethyl ester were obtained by Vilsmeier reaction with dimethylformamide. By treating the derivatives of nickel(II) 20-(2-formyl)-chlorin and nickel(II) 3-(2-formylvinyl)-20-(2-formyl)-chlorin with trifluoracetic acid, the removal of the central nickel(II) ion was accomplished. The derivatives of 20-(2-formyl)-chlorin and 3-(2-formylvinyl)-20-(2-formyl)-chlorin demonstrated considerable bathochromic shift of the major absorption band in the red region of the optical spectrum.  相似文献   

10.
Synthesis and Crystal Structure of LiPdAlF6 and PdZrF6 . For the first time single crystals of the new compounds LiPdAlF6 and PdZrF6 have been obtained. LiPdAlF6 (blue) crystallizes trigonal, space group P3 1c—D (No. 163; LiCaAlF6-type [2]), in an ordered structure variant of the Li2[ZrF6]-structure [3], with a=497.21(9) pm, c=914.0(9) pm and Z=2. PdZrF6 (also blue) is isotypic with LiSbF6 [4] and crystallizes trigonal-rhomboedric with a=552,3(1) pm, c=1 447,5(4) pm, space group R 3 —C (No. 148) and Z=3.  相似文献   

11.
A new strategy for the synthesis of 6-hydroxyalkyl- and 6-hydroxyaralkyl-6H-dibenz[c,e][1,2]oxaphosphorin 6-oxides 3 was achieved by the reaction of 2-(2-hydroxyphenyl)phenylphosphonic acid ( 1 ) with various carbonyl compounds 2 . The desired products 3 were obtained in acceptable yields.  相似文献   

12.
Anotation to Compounds MPtF6 (M = Ni, Cd) Yellow single crystals of M11PtF6 (M11 = Ni, Cd) have been obtained for the first time and investigated by X-ray methods. The powder data of the compounds are confirmed. Both samples are isostructural to LiSbF6, space group R3 -C (Nr. 148) with a = 500.5(3) pm, c = 1375.6(7) pm for NiPtF6 and a = 511.56(9) pm, c = 1460.3(4) pm for CdPtF6, Z = 3.  相似文献   

13.
Sun C  Li Y  Wang E  Xiao D  An H  Xu L 《Inorganic chemistry》2007,46(5):1563-1574
By synthesizing the novel molybdenum arsenate complexes, we have obtained eight new structures, namely, (4,4'-bipy)[Zn(4,4'-bipy)2(H2O)2]2[(ZnO6)(AsIII3O3)2Mo6O18].7H2O, 1, [Zn(phen)2(H2O)]2[(ZnO6)(AsIII3O3)2Mo6O18].4H2O, 2, [Zn(2,2'-bipy)2(H2O)]2[(ZnO6)(AsIII3O3)2Mo6O18].4H2O, 3, [Zn(H4,4'-bipy)2(H2O)4][(ZnO6)(AsIII3O3)2Mo6O18].8H2O, 4, (H24,4'-bipy)[CuI(4,4'-bipy)]2[H2AsV2Mo6O26].H2O, 5, (H24,4'-bipy)3[AsV2Mo6O26].4H2O, 6, (H24,4'-bipy)3[AsV2Mo6O26(H2O)].4H2O, 7, and (H24,4'-bipy)2.5(H3O)[AsV2Mo6O26(H2O)].1.25H2O, 8 (4,4'-bipy = 4,4'-bipyridine, 2,2'-bipy = 2,2'-bipyridine, phen = 1,10-phenanthroline). These structures were determined by single-crystal X-ray diffraction analysis and were further characterized by elemental analysis, IR, XPS spectroscopy, and TG analysis. The structure of 1 is constructed from two-dimensional square gridlike sheets linked by the polyanions [(ZnO6)(AsIII3O3)2Mo6O18]4- via hydrogen-bonding interactions to form a three-dimensional supramolecular framework with two types of channels. Compounds 2 and 3 display similar bisupported structures. Compound 4 features a three-dimensional supramolecular architecture. Compound 5 possesses a 1D infinite ladderlike ribbon. Compounds 6-8 are discrete structures exhibiting three isomeric forms of [HxAs2Mo6O26](6-x)-. Furthermore, compound 8 represents a new isomer B'-[As2Mo6O26(H2O)]6-. In addition, the fluorescent properties of compounds 1-3 are reported.  相似文献   

14.
Two intramolecular stabilized arylaluminum dihydrides, (2-(NEt2CH2)-6-MeC6H3)AlH2 (1) and (2,6-(NEt2CH2)2C6H3)AlH2 (2), were prepared by reducing the corresponding dichlorides with an excess of LiAlH4 in diethyl ether. Reactions of 1 and 2 with elemental selenium afforded the dimeric arylaluminum selenides [(2-(NEt2CH2)-6-MeC6H3)AlSe]2 (3) and [(2,6-(NEt2CH2)2C6H3)AlSe]2 (4). Reaction of 2 with metallic tellurium gave the dimeric arylaluminum telluride [(2,6-(NEt2CH2)2C6H3)AlTe]2 (5). The possible reaction pathway is discussed, and molecular structures determined by single-crystal X-ray analyses are presented for 3 and 5.  相似文献   

15.
Reaction of copper(I) iodide with pyridine-2-thione (2-SC5H4NH) and 1,2-bis(diphenylphosphino)ethane (dppe) in a CH3CN-CHCl3 mixture yielded a triangular cluster, [Cu3I3(mu2-P,P-dppe)3 (eta1-SC5H4NH)], 1. Similar reaction with 2-SC5H4NH and a series of diphosphanes, Ph2P-X-Ph2P {X = -CH2- (dppm), -(CH2)3- (dppp), -(CH2)4- (dppb), -CH=CH- (dppen)}, gave a novel iodo-bridged hexanuclear Cu(I) linear polymer,{Cu6(mu3-SC5H4NH)4 (mu2-SC5H4NH)2 (I4)(mu-I)2-}n x 2nCH3CN, 2. Reactions of copper(I) iodide/copper(I) bromide with 1,3-imidazolidine-2-thione (SC3H6N2) in a CH3CN-CHCl3 mixture yielded hexanuclear Cu(I) linear chain polymers, [{Cu6(mu3-SC3H6N2)2 (mu2-SC3H6N2)4X2 (mu-X)4}n] (X = Br, 4; I, 5). In compound 1, two iodide atoms and one dppe form the dinuclear Cu(mu2-I)2 (mu2-dppe)Cu core, and two dppe ligands bridge this core with the third Cu(I) center coordinated to 2-SC5H4NH via the S atom. The chain polymer 2 has a centrosymmetric hexanuclear central core, Cu6S6I4 (mu-I)2--, formed by dimerization of six-membered trinuclear motifs, Cu3(mu2-SC3H6N2)3I3 via (mu3-S) bonding modes of the thione ligand, and has four terminal and two bridging iodine atoms in trans-orientations. Linear chains are separated by the nonbonded acetonitrile molecules. In 4 and 5, three copper(I) bromide or copper(I) iodide moieties and three SC3H6N2 ligands combined via bridging S donor atoms to form the six-membered trinuclear Cu3(mu2-SC3H6N2)3I3 cores which polymerized via S and X atoms in a side-on fashion to form linear chain polymers, [{Cu6(mu3-SC3H6N2)2 (mu2-SC3H6N2)4X2(mu-X)4}n]. The (mu3-S) modes of bonding of neutral heterocyclic thioamides are first examples, as are trinuclear cluster and linear polymers rare examples in copper chemistry.  相似文献   

16.
Starting from tetraacetylribofuranose and 6-chloropurine, in the presence of was synthesized for the first time under microwave irradiation. The title compound 6-chloro-9-β-D-purinenucleoside (Ⅳ) and 6-methoxy-9-β-D-purinenucleoside (Ⅴ) was easily obtained by treatment of the intermediate (Ⅲ) with Na2CO3 in CH3OH solution refluxing for 8min and 2hr respectively.  相似文献   

17.
以鸟嘌呤为核苷为原料,经酯化、再在缩合剂4-氯苯磷酰二氯和1,2,4-三氮唑存在下与吡啶反应,得鸟嘌呤核苷N-6吡啶盐中间体(2),该中间体2分别与NH~3/CH~3OH、Et~3N/CH~3OH、Et~EN/CH~3CH~2OH在室温反应,可方便的合成6-NH~2、6-OCH~3和6-OCH~2CH~3-9-(β-D-呋喃核糖)鸟嘌呤衍生物。  相似文献   

18.
By reaction of 6-[N-(2-hydroxyethyl)-N-methyl]aminopurine ( 2a ) and of the corresponding 3-hydroxypropyl derivative 2b with thionyl chloride a bridge to N(1) is formed yielding 5 and 6 , respectively, whereas from 6-[N-(4-hydroxybutyl)-N-methyl]aminopurine ( 2c ) the 4-chlorobutyl compound 4 is obtained, which cyclizes in alkaline medium to the C(6)-N(7) bridged compound 7 . A related cyclization to 11a–11f is observed when 6-chloropurines are reacted with 3-alkyl-1,3-oxazolidines or 3-methyl-1,3-thiazolidine.  相似文献   

19.
The preparation of 6(A)-deoxy-6(A)-(6-(2-(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)acetamido)hexylamino)-alpha-cyclodextrin, 3, 6(A)-deoxy-6(A)-(6-(2-(1,4,7,10,13-pentaoxa-16-azacyclooctadecan-16-yl)acetamido)hexylamino)-alpha-cyclodextrin, 4, and their beta-cyclodextrin analogues, 5 and 6, are described. (1)H (600 MHz) ROESY NMR spectra of the C(6) substituted beta-cyclodextrins, 5 and 6, are consistent with the intramolecular complexation of their azacyclopentadecanyl- and azacyclooctadecanyl(acetamido)hexylamino substituents in the beta-cyclodextrin annulus in D(2)O at pD = 8.5 whereas those of their alpha-cyclodextrin analogues, 3 and 4 are not complexed in the alpha-cyclodextrin annulus. This is attributed to the monoazacoronand components of the substituents being able to pass through the beta-cyclodextrin annulus whereas they are too large to pass through the alpha-cyclodextrin annulus. However, the substituents of 3 and 4 are intermolecularly complexed by beta-cyclodextrin to form pseudo [2]-rotaxanes. Metallocyclodextrins are formed by 5 through complexation by the monoazacoronand substituent component for which log (K/dm(3) mol(-1))= <2, 6.34 and 5.38 for Ca(2+), Zn(2+) and La(3+), respectively, in aqueous solution at 298.2 K and I= 0.10 mol dm(-3)(NEt(4)ClO(4)).  相似文献   

20.
IntroductionTheshikimatepathwayisanimportantbiosyn theticsequencein plants ,fungiandmicroorganismsfortheconversionofcarbohydratestothearomaticaminoacids (L phenylalanine ,L tyrosineandL tryptophan)andprecursorstothefolatecoenzymes ,alkaloidsandvitamins[1] .As…  相似文献   

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