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1.
Two new spin-crossover complexes, [Fe(Medpq)(py) 2(NCS) 2] · py · 0.5H 2O (1) and [Fe(Medpq)(py) 2(NCSe) 2] · py (2) (Medpq = 2-methyldipyrido[3,2- f:2′,3′- h]-quinoxaline, py = pyridine), have been synthesized. The crystal structures were determined at both room temperature (298 K) and low temperature (110 K). Complexes 1 and 2 crystallize in the orthorhombic space group Pbca and monoclinic space group P2 1/ n, respectively. In both complexes, the distorted [FeN 6] octahedron is formed by six nitrogen atoms from Medpq, the trans pyridine molecules and the cis NCX − groups. The thermal spin transition is accompanied by the shortening of the mean Fe–N distances by 0.194 Å for 2. The mononuclear [Fe(Medpq)(py) 2(NCS) 2] and [Fe(Medpq)(py) 2(NCSe) 2] neutral species interact each other via π-stacking, resulting in a one-dimensional extended structure for both 1 and 2. There exist C–HX (X = S, Se) hydrogen bonds for both complexes. Variable-temperature magnetic susceptibility measurements and Mössbauer spectroscopy reveal the occurrence of a gradual spin transition. The transitions are centered at T1/2 = 120 K for 1 and T1/2 = 180 K for 2, respectively. 相似文献
2.
The metal ion complexing properties of the ligand HQC (8-hydroxyquinoline-2-carboxylic acid) are reported. The structures of [Zn(HQCH) 2] · 3H 2O (1) and [Cd(HQCH) 2] · 3H 2O (2) were determined (HQCH = HQC with phenol protonated). Both 1 and 2 are triclinic, space group , with Z = 2. For 1 a = 7.152(3), b = 9.227(4), c = 15.629(7) Å, = 103.978(7)°, β = 94.896(7)°, γ = 108.033(8)°, R = 0.0499. For 2 a = 7.0897(5), b = 9.1674(7), c = 16.0672(11) Å, = 105.0240(10)°, β = 93.9910(10)°, γ = 107.1270(10)°, R = 0.0330. In 1 the Zn has a distorted octahedral coordination geometry, with Zn–N of 2.00 and 2.15 Å, and Zn–O to the protonated phenolic oxygens of 2.431 and 2.220 Å. The structure of 2 is similar, with Cd–N bonds of 2.220 and 2.228 Å, with Cd–O bonds to the protonated phenolate oxygens of 2.334 and 2.463 Å. The structures of 1 and 2, and isomorphous Ni(II) and Co(II) HQC complexes reported in the literature, show very interesting short (<2.5 Å) O–O distances in H-bonds involving the protons on the coordinated phenolates and lattice water molecules. These are discussed in relation to the possible role of short low-energy H-bonds in alcohol dehydrogenase in mediating the transfer of the hydroxyl proton of the alcohol to an adjacent serine oxygen. The formation constants for HQC are determined by UV–Visible spectroscopy at 25 °C in 0.1 M NaClO4 with Mg(II), Ca(II), Sr(II), Ba(II), La(III), Gd(III), Zn(II), Cd(II), Ni(II), Cu(II), and Pb(II). These show greatest stabilization with metal ions with an ionic radius above 1.0 Å. This is as would be expected from the fact that HQC forms two five-membered chelate rings on complex-formation, which favors larger metal ions. The ligand design concept of using rigid aromatic backbones in ligands to achieve high levels of preorganization, and hence the high log K values (for a tridentate ligand) and strong metal ion selectivities observed for HQC, is discussed. 相似文献
3.
The crystal structure of tri- O-ethylamylose has been solved by stereochemical conformation and packing analysis and by X-ray fibre diagram analysis. The unit cell is orthorhombic, space group P2 12 12 1, with = 16.13 (± 0.04) Å, b = 11.66 (± 0.02) Å, and c (fibre repeat) = 15.48 (± 0.02) Å. Density measurements, together with the observation of only a fourth-order meridional reflection, indicated that portions of two four-fold helices pass through the unit cell. The actual chain conformation is that of a 4 3 helix with the EtO-6 group in the tg (trans to O-5, and gauche to C-4) position. The tri- O-ethylamylose structure is compared with those of other amylose derivatives. 相似文献
4.
The trinuclear complexes [Ag(PR 3) 2] 2[Ni(mnt) 2] and [AgL] 2[Ni(mnt) 2] have been prepared by reactions of (NEt 4) 2[Ni(mnt) 2] and Ag 2SO 4 with alkyl phosphines (PR 3=P(CH 3) 3 (PMe 3) for 1, P(C 2H 5) 3 (PEt 3) for 2 and P(C 6H 11) 3 (PCy 3) for 3), or with chelating diphosphines (L=1,1′-bis(diphenylphosphino)ferrocene (dppf) for 4 and bis(diphenylphosphino)methane (dppm) for 5). The structures of all the complexes have been determined by X-ray crystallography. Interactions between the [Ag(PR 3) 2] + and [Ni(mnt) 2] 2− groups occur in compounds 1 and 2 with Ni---Ag distances of 3.063(4) and 2.9311(6) Å, respectively. Only one sulfur atom of each mnt ligand bridged [Ag(PR 3) 2] + cations and [Ni(mnt) 2] 2− anions in compound 1 through 3 with Ag---S distances of about 2.7 Å. There is no interaction between Ag and Ni in compound 3 due to the flexibility of the cyclohexyl groups. Interactions between [AgL] + and [Ni(mnt) 2] 2− groups also occur in compound 4 with a much shorter Ag---Ni distance of 2.7213(7) Å, while silver atoms and the NiS 4 plane in compound 4 make a chair conformation with Ag---S distances of about 2.8 Å. In compound 5, dppm bridges two silver atoms, and interaction between silver atoms occurs at a distance of 2.9859(11) Å, and only one sulfur atom of mnt is used to bridge Ni and Ag atoms with Ag---S distances of 2.582(3) and 2.663(3) Å. 相似文献
5.
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
6.
The methanothermal reactions of M(CO) 6 (M = Mo, W) with Na 2S 2 gave a series of homonuclear clusters [{M(CO) 4} n(MS 4)] 2− (M=Mo, W; N=1, 2), i.e. (Ph 4P) 2[(CO) 4Mo(MoS 4)] (I), (Ph 4P) 2[(CO) 4W(WS 4)] (II), (Ph 4P) 2[(CO) 4Mo(MoS 4)Mo(CO) 4] (III) and (Ph 4P) 2[(CO) 4W(WS 4)W(CO) 4] (IV). The two dimers, I and II, as well as the two trimers, III and IV, are isostructural to each other, respectively. All compounds crystallize in the triclinic space group
with Z=2. The cell dimensions are: a=12.393(8), b=19.303(9), c=11.909(6) Å, =102.39(5), β=111.54(5), γ=73.61(5)°, V=2522(3) Å 3 at T=23 °C for I; a=12.390(3), b=19.314(4), c=11.866(2) Å, =102.66(2), β=111.49(1), γ=73.40(2)°, V=2511(1) Å 3 at T=23 °C for II; a=11.416(3), b=22.524(4), c=10.815(4) Å, =91.03(2), β=100.57(3), γ=88.96(2)°, V=2733(1) Å 3 at T=−100 °C for III, a=11.498(1), b=22.600(4), c=10.864(3) Å, =90.92(2), β=100.85(1), γ=88.58(1)°, V=2771(2) Å 3 at T=23 °C for IV. The dimers are each formed by the coordination of the tetrathiometalate as a bidentate chelating ligand to an M(CO) 4 fragment while addition of another M(CO) 4 fragment to the dimers results in the trimers. All compounds contain both tetrahedral and octahedral metal centers with the formal 6+ and 0 oxidation states, respectively. 相似文献
7.
The complex [(NH 3) 5CoO 3SCF 3](CF 3SO 3) 2 reacts with excess NaNCO in warm acetone solution to give, stereoselectively, a Schiff base complex (40%) which has been characterized by standard NMR techniques as one of the six isomers of [Co{NH 2C(CH 3) 2CH 2C(CH 3)=NH} 2(NH 3)NCO](ClO 4) 2 · H 2O, confirmed by a single crystal X-ray structural analysis. Schiff base formation in non-basic conditions for kinetically inert Co(III) complexes is unprecedented. Also, this is only the second cyanate complex of pentaaminecobalt(III) to be structurally characterized (CoNCO: Co–N, 1.908 Å; N–C, 1.152 Å; C–O, 1.206 Å; Co–N–C, 170°; N–C–O, 177°). 相似文献
8.
The hydrothermal reactions of (Ph 4P)[VO 2Cl 2] and H 2C 2O 4 at 150 and 125°C yield (Ph 4P) 2[V 2O 2(H 2O) 2(C 2O 4) 3]·4H 2O (1) and (Ph 4P)[VOCl(C 2O 4)] (2), respectively. The structure of the molecular anion of 1 consists of a binuclear unit of oxovanadium(IV) octahedra bridged by a bisbidentate oxalate group. The VO 6 coordination geometry at each vanadium site is defined by a terminal oxo group, an aquo ligand, and four oxygen donors — two from the bisbidentate bridging oxalate and two from the terminal bidentate oxalate. The structure of 2 consists of discrete Ph 4P + cations occupying regions between [VOCl(C 2O 4)] −∞ spiral chains. The structure of the one-dimensional anionic chain exhibits V(IV) octahedra bridged by bisbidentate oxalate groups. Crystal data: 1·4H 2O, monoclinic P2 1/ n, A = 12.694(3), B = 12.531(3), C = 17.17(3) Å, β = 106.32(2)°, V = 2621.3(13) Å 3, Z = 2, Dcalc = 1.501 g cm −3, structure solution and refinement converged at a conventional residual of 0.0518; 2, tetragonal P4 3, A = 12.145(2), C = 15.991(3) Å, V = 2358.7(12) Å 3, Z = 4, R = 0.0452. 相似文献
9.
New mixed metal complexes SrCu 2(O 2CR) 3(bdmap) 3 (R = CF 3 (1a), CH 3 (1b)) and a new dinuclear bismuth complex Bi 2(O 2CCH 3) 4(bdmap) 2(H 2O) (2) have been synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction analyses. Thermal decomposition behaviors of these complexes have been examined by TGA and X-ray powder diffraction analyses. While compound 1a decomposes to SrF 2 and CuO at about 380°C, compound 1b decomposes to the corresponding oxides above 800°C. Compound 2 decomposes cleanly to Bi 2O 3 at 330°C. The magnetism of 1a was examined by the measurement of susceptibility from 5–300 K. Theoretical fitting for the susceptibility data revealed that 1a is an antiferromagnetically coupled system with g = 2.012(7), −2 J = 34.0(8) cm −1. Crystal data for 1a: C 27H 51N 6O 9F 9Cu 2Sr/THF, monoclinic space group P2 1/ m, A = 10.708(6), B = 15.20(1), C = 15.404(7) Å, β = 107.94(4)°, V = 2386(2) Å 3, Z = 2; for 1b: C 27H 60N 6O 9Cu 2Sr/THF, orthorhombic space group Pbcn, A = 19.164(9), B = 26.829(8), C = 17.240(9) Å, V = 8864(5) Å 3, Z = 8; for 2: C 22H 48O 11N 4Bi 2, monoclinic space group P2 1/ c, A = 17.614(9), B = 10.741(3), C = 18.910(7) Å, β = 109.99(3)°, V = 3362(2) Å 3, Z = 4. 相似文献
10.
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
11.
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
12.
With exposure to trace amounts of air and moisture, the Cr 2(II, II) complex Cr 2(μ-3,5Cl 2-form) 4, where 3,5Cl 2-form is [(3,5-Cl 2C 6H 3)NC(H)N(3,5-Cl 2C 6H 3) −], undergoes an oxidative addition reaction. Structural information from the X-ray crystal structure of the edge-sharing bioctahedral (ESBO) Cr 2(III, III) product Cr 2(μ-OH) 2(μ-3,5Cl 2-form) 2(η 2-3,5Cl 2-form) 2 (1) indicates 1 has a significantly longer Cr–Cr distance [2.732(2) Å] than Cr 2(μ-3,5Cl 2-form) 4 [1.9162(10) Å], but the shortest Cr–Cr distance in an ESBO Cr 2(III, III) complex recorded to date. 相似文献
13.
Four complexes of the type [Cu 4I 4(CH 3CN) 2(L) 2], L = aniline derivative: Cu 4I 4(CH 3CN) 2(2,6-dimethylaniline) 2 (I), triclinic,
, a = 12.449(3), B = 14.108(6), C = 10.606(4) Å, = 73.46(3), β = 95.00(2), γ = 73.42(3)°, V = 1682.3(10) Å 3; Cu 4I 4(CH 3CN) 2( o-ethylaniline) 2 (II), triclinic, , V = 1734.0(8) Å 3; Cu 4I 4(CH 3CN) 2(6-ethyl- o-toluidine) 2 (III), orthorhombic, Pnam, a = 14.976(6), b = 21.187(6), C = 12.545(2) Å, V = 3980.7(2) Å 3; Cu 4I 4(CH 3CN) 2( p-anisidine) 2 (IV), monoclinic, A2/ a, A = 20.032(10), B = 7.863(1), C = 18.715(9) Å, β = 101.56(4)°, V = 2888.0(2) Å 3; were examined by single crystal X-ray diffraction. Complexes I and II have no internal symmetry elements, III has an internal mirror and IV has a two-fold axis. Ab initio calculations based on the atomic positional parameters of complexes containing the three types of symmetry elements reveal HOMO orbitals to be dominated by the p orbitals of the iodine atoms whereas the LUMO orbitals contain major contributions from copper based p orbitals. 相似文献
14.
The chloro complexes trans-[Pt(Me)(Cl)(PPh 3) 2], after treatment with AgBF 4, react with 1-alkynes HC---C---R in the presence of NEt 3 to afford the corresponding acetylide derivatives trans-[Pt(Me) (C---C---R) (PPh 3) 2] (R = p-tolyl (1), Ph (2), C(CH 3) 3 (3)). These complexes, with the exception of the t-butylacetylide complex, react with the chloroalcohols HO(CH 2) nCl ( n = 2, 3) in the presence of 1 equiv. of HBF 4 to afford the alkyl(chloroalkoxy)carbene complexes trans-[Pt(Me) {C[O(CH 2) nCl](CH 2R) } (PPh 3) 2][BF 4] (R = p-tolyl, N = 2 (4), N = 3 (5); R=Ph, N = 2 (6)). A similar reaction of the bis(acetylide) complex trans-[Pt(C---C---Ph) 2(PMe 2Ph) 2] with 2 equiv. HBF 4 and 3-chloro-1-propanol affords trans-[Pt(C---CPh) {C(OCH 2CH 2CH 2Cl)(CH 2Ph) } (PMe 2Ph) 2][BF 4] (7). T alkyl(chloroalkoxy)-carbene complex trans-[Pt(Me) {C(OCH 2CH 2Cl)(CH 2Ph) } (PPh 3) 2][BF 4] (8) is formed by reaction of trans-[Pt(Me)(Cl)(PPh 3) 2], after treatment with AgBF 4 in HOCH 2CH 2Cl, with phenylacetylene in the presence of 1 equiv. of n-BuLi. The reaction of the dimer [Pt(Cl)(μ-Cl)(PMe 2Ph)] 2 with p-tolylacetylene and 3-chloro-1-propanol yields cis-[PtCl 2{C(OCH 2CH 2CH 2Cl)(CH 2C 6H 4- p-Me}(PMe 2Ph)] (9). The X-ray molecular structure of (8) has been determined. It crystallizes in the orthorhombic system, space group Pna2 1, with a = 11.785(2), B = 29.418(4), C = 15.409(3) Å, V = 4889(1) Å 3 and Z = 4. The carbene ligand is perpendicular to the Pt(II) coordination plane; the PtC(carbene) bond distance is 2.01(1) Å and the short C(carbene)-O bond distance of 1.30(1) Å suggests extensive electronic delocalization within the Pt---C(carbene)---O moietry. 相似文献
15.
1-emthylimidazoline-2(3H)-thione (mimtH) reacts with copper(II) sulphate pentahydrate in aqueous acetone to produce the dinuclear complex, Cu 2(mimtH) 5SO 4 · 3H 2O; the formula has been established by a combination of chemical and thermal analysis. The monoclinic crystals, (space group Pc, Z = 2), contain dinuclear cations, sulphate ions and water molecules. The dinuclear cation, Cu 2(mimtH) 52+, consists of two trigonal copper(I) atoms, four terminal, monodentate, S-donating mimtH molecules and one S-bridging (μ 2) mimtH molecule. Some average dimensions are:Cu---S, 2.258 Å and S---Cu---S, 120.0°; the Cu---S---Cu bridging angle is 94.8° and the Cu---Cu separation distance is 3.308 Å. 相似文献
16.
PufX organises the photosynthetic reaction centre–light harvesting complex 1 (RC–LH1) core complex of Rhodobacter sphaeroides and facilitates quinol/quinone exchange between the RC and cytochrome bc1 complexes. The structure of PufX in organic solvent reveals two hydrophobic helices flanked by unstructured termini and connected by a helical bend. The proposed location of basic residues and tryptophans at the membrane interface orients the C-terminal helix along the membrane normal, with the GXXXG motifs in positions unsuitable as direct drivers of dimerisation of the RC–LH1 complex. The N-terminal helix is predicted to extend 40 Å along the membrane interface. 相似文献
17.
An improved synthetic procedure for pentabenzylcyclopentadiene Bz 5C 5H was developed. Six new organomolybdenum and organotungsten halides η 5-Bz 5C 5M(CO) 3X(M = Mo, W; X = Cl, Br, I) were syntesized through the reaction of η 5-Bz 5C 5M(CO) 3Li (derived from Bz 5C 5H, n-BuLi and M(CO) 6) with PCl 3, PBr 3 or I 2 and characterized by elemental analysis, IR and 1H NMR spectroscopy. The structure of η 5-Bz 5C 5Mo(CO) 3I was determined by single-crystal X-ray diffraction techniques. It crystallized in the monoclinic space groupp P2/ c with cell parameters a = 13.294(4), B = 15.147(4), C = 19.027(3) Å, β = 108.32(2)°, V = 3637(2) Å 3, Z = 4 and Dx = 1.50 g cm −3. The final R value was 0.035 for 4564 observed reflections. 相似文献
18.
Reaction of LaCl 3·7H 2O containing small amounts of La(NO 3) 3·7H 2O as an impurity with 12-crown-4 or 18-crown-6 in 3:1 CH 3CN:CH 3OH resulted in the isolation of the mixed anion complexes [LaCl 2(NO 3)(12-crown-4)] 2, [La(NO 3)(OH 2) 4(12-crown-4)]Cl 2·CH 3CN and [LaCl 2(NO 3)(18-crown-6)]. The nine-coordinate dimer, [LaCl 2(NO 3)(12-crown-4)] 2, has all of the anions in the inner coordination sphere and La 3+ has a capped square antiprismatic geometry. It crystallizes in the orthorhombic space group Pbca with (at −150 °C) a = 12.938(6), B = 15.704(3), C = 13.962(2) Å, and Dcalc = 2.08 g cm −3 for Z = 4. The second complex isolated from the same reaction, [La(NO 3)(OH 2) 4(12-crown-4)]Cl 2·CH 3CN, has the bidentate nitrate anion in the inner coordination sphere but the two chloride anions are in a hydrogen bonded outer sphere. This complex is ten-coordinate 4A,6B-expanded dodecahedral and crystallizes in the monoclinic space group P2 1 with (at 20 °C) A = 7.651(2), B = 11.704(7), C = 11.608(4) Å, β = 95.11(2)°, and Dcalc = 1.80 g cm −3 for Z = 2. The 18-crown-6 complex, [LaCl 2(NO 3)(18-crown-6)], has all inner sphere anions and has ten-coordinate 4A,6B-expanded dodecahedral La 3+ centers. It crystallizes in the orthorhombic space group Pbca with (at 20 °C) a = 14.122(7), B = 13.563(5), C = 19.311(9) Å, and Dcalc = 1.89 g cm −3 for Z = 8. 相似文献
19.
The reactions of cadmium halides with the 15-membered macrocyclic crown ethers, 15-crown-5 and benzo-15-crown-5, have been carried out and six new complexes have been isolated and structurally characterized. Metal to ligand stoichiometries of 1:1, 2:1, 3:1 and 3:2 have been observed with a variety of different formulations. Examples of charge separated ion pairs ([(NH 4)(benzo-15-crown-5) 2] 2[Cd 2I 6]), halogen bridged monomers, dimers or polymers ([Cd(15-crown-5)(OHMe)(μ-Br)CdBr 3], [Cd(15-crown-5)(μ-Br) 2CdBr(μ-Br)] 2(isolated from the same reaction mixture) and [(CdCl 2) 2CdCl 2(15-crown-5)] n), and hydrogen bonded finite chains or polymers ([(Cd(OH 2) 2(15-crown-5)][CdI 3(OH 2)] 2·2(15-crown-5)·2CH 3CN and [CdI 2(OH 2) 2(THF)]·benzo-15-crown-5) have been isolated. Three different types of 15-crown-5 coordination modes have been observed in these complexes. In-cavity coordination resulting in pentagonal bipyramidal geometries about Cd 2+ was observed in [(CdCl 2) 2CdCl 2(15-crown-5)] n, [Cd(15-crown-5)(OHMe)(μ-Br)CdBr 3], and [Cd(OH 2) 2(15-crown-5)][CdI 3(OH 2)] 2·2(15-crown-5)·2CH 3CN, [Cd(15-crown-5)(μ-Br) 2CdBr(μ-Br)] 2 displays out-of-cavity coordination with one etheric donor distorted into an axial position of a distorted pentagonal bipyramid. The third coordination mode is secondary sphere coordination via hydrogen bonding which is observed for [Cd(OH 2) 2(15-crown-5)][CdI 3(OH 2)] 2·2(15-crown-5)·2CH 3CN. The good fit of Cd 2+ within the cavity of 15-crown-5 results in shorter bonding contacts and a more narrow distribution in Cd---O values (2.273(7)-2.344(6) Å) than observed for cadmium halide complexes of 18-crown-6 (Cd---O = 2.69(1)–2.81(1) Å). 相似文献
20.
Kinetic results are reported for intramolecular PPh 3 substitution reactions of Mo(CO) 2(η 1-L)(PPh 3) 2(SO 2) to form Mo(CO) 2(η 2-L)(PPh 3)(SO 2) (L = DMPE = (Me) 2PC 2H 4P(Me) 2 and dppe=Ph 2PC 2H 4PPh 2) in THF solvent, and for intermolecular SO 2 substitutions in Mo(CO) 3(η 2-L)(η 2-SO 2) (L = 2,2′-bipyridine, dppe) with phosphorus ligands in CH 2Cl 2 solvent. Activation parameters for intramolecular PPh 3 substitution reactions: Δ H≠ values are 12.3 kcal/mol for dmpe and 16.7 kcal/mol for dppe; Δ S≠ values are −30.3 cal/mol K for dmpe and −16.4 cal/mol K for dppe. These results are consistent with an intramolecular associative mechanism. Substitutions of SO 2 in MO(CO) 3(η 2-L)(η 2-SO 2) complexes proceed by both dissociative and associative mechanisms. The facile associative pathways for the reactions are discussed in terms of the ability of SO 2 to accept a pair of electrons from the metal, with its bonding transformations of η 2-SO 2 to η 1-pyramidal SO 2, maintaining a stable 18-e count for the complex in its reaction transition state. The structure of Mo(CO) 2(dmpe)(PPh 3)(SO 2) was determined crystallographically: P2 1/ c, A=9.311(1), B = 16.344(2), C = 18.830(2) Å, ß=91.04(1)°, V=2865.1(7) Å 3, Z=4, R( F)=3.49%. 相似文献
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