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1.
The stable carbon and oxygen isotopic compositions of soil carbonate were measured on an eolian loess and red clay sequence at Lingtai, the Chinese Loess Plateau. This sequence is composed of 130 m of Tertiary red clay deposits with a basal age of 7.05 Ma overlain by 175 m of Pleistocene loess. In the field we identified ca. 110 carbonate nodule horizons in the red clay and 27 nodule horizons in the loess. These carbonate nodule horizons are formed by leaching and re-precipitation of carbonate from the eolian material. The δ 13C record of soil carbonate indicates a major expansion of C 4 plants at ca. 4.0 Myr in the Loess Plateau. This event is comparable in timing with the expansion of C 4 plants in northern North America ( Cerling et al., 1997. Nature 389, 153–158) but is ca. 3 million years later than the C 4 biomass expansion in Pakistan ( Quade et al., 1989. Nature 342, 163–166). The pedogenic characteristics of the soils and the δ 18O record in the red clay suggest that the C 4 plant expansion in the Loess Plateau was not driven by local climatic changes, which may support Cerling et al.'s (1997) assertion that the decline of atmospheric CO 2 levels in the Neogene is responsible for this global vegetation change. Our record also implies that the Tibetan Plateau could have been uplifted to a critical height in the late Miocene, thus resulting in the formation of the atmospheric Great East-Asia Trough. 相似文献
2.
[NBu n4] 2[W(C 3Se 5) 3] (C 3Se 52− = 1,3-diselenole-2-selone-4,5- diselenolate(2−)) was prepared by the reaction of Na 2[C 3Se 5] with WCl 6 in ethanol, followed by addition of [NBu n4]Br. The cyclic voltammogram in dichloromethane exhibits two oxidation peaks at −0.04 and +0.03 V (versus SCE). The complex reacted with [Fe(C 5Me 5) 2][BF 4], iodine or [TTF] 3[BF 4] 2 (TTF ·+ = the tetrathiafulvalenium radical cation) in acetonitrile to afford the oxidized complexes [Fe(C 5Me 5) 2] 0.5[W(C 3Se 5) 3], [NBu n4] 0.1[W(C 3Se 5) 3] and [TTF] 0.5[W(C 3Se 5) 3], respectively. Current-controlled electrochemical oxidation of the complex in acetonitrile gave [NBu n4] 0.6[W(C 3Se 5) 3]. The oxidized complexes exhibit electrical conductivities of 4.7×10 −5−1.5×10 −3 S cm −1 at room temperature measured for compacted pellets. Electronic absorption, IR and ESR spectra of these complexes are discussed. 相似文献
3.
Panicum milioides, a naturally occurring species with C 4-like Kranz leaf anatomy, is intermediate between C 3 and C 4 plants with respect to photorespiration and the associated oxygen inhibition of photosynthesis. This paper presents direct evidence for a limited degree of C 4 photosynthesis in this C 3-C 4 intermediate species based on: 1. (a) the appearance of 24% of the total 14C fixed following 4 s photosynthesis in 14CO2-air by excised leaves in malate and aspartate and the complete transfer of label from the C4 acids to Calvin cycle intermediates within a 15 s chase in 12CO2-air; 2. (b) pyruvate- or alanine-enhanced light-dependent CO2 fixation and pyruvate stimulation of oxaloacetate- or 3-phosphoglycerate-dependent O2 evolution by illuminated mesophyll protoplasts, but not bundle sheath strands; and 3. (c) NAD-malic enzyme-dependent decarboxylation of C4 acids at the C-4 carboxyl position, C4 acid-dependent O2 evolution, and 14CO2 donation from [4-14C]C4 acids to Calvin cycle intermediates during photosynthesis by bundle sheath strands, but not mesophyll protoplasts.
However, P. milioides differs from C4 plants in that the activity of the C4 cycle enzymes is only 15 to 30% of a C4 Panicum species and the Calvin cycle and phosphoenolpyruvate carboxylase are present in both cell types. From these and related studies (Rathnam, C.K.M. and Chollet, R. (1979) Arch. Biochem. Biophys. 193, 346–354; (1978) Biochem. Biophys. Res. Commun. 85, 801–808) we conclude that reduced photorespiration in P. milioides is due to a limited degree of NAD-malic enzyme-type C4 photosynthesis permitting an increase in pCO2 at the site of bundle sheath, but not mesophyll, ribulosebisphosphate carboxylase-oxygenase. 相似文献
4.
Cp #2Yb (Cp #=C 5H 4(CH 2) 2NMe 2) has been obtained by reaction of YbI 2(THF) 2 with 2 equiv. of C 5H 4(CH 2CH 2NMe 2)K in THF. The X-ray structure analysis shows a bent structure with intramolecular coordination of both nitrogen atoms to ytterbium. The reaction of C 60-fullerene with Cp #2Yb leads to the formation of the fullerenide derivative [Cp #2Yb] 2C 60, which shows an ESR signal in the solid state and in THF solution at room temperature (solid: Δ H = 50 G, G = 1.9992; solution: Δ H = 10 G, G = 2.0001) and a magnetic moment of 3.6 BM. The lutetium fullerenides CpLu(C 60)(DME) (3) and Cp *Lu(C 60)(DME)(C 6H 5CH 3) (4), (Cp = η 5−C 5H 5, Cp * = η 5−C 5Me 5), were obtained by reaction of C 60 with CpLu(C 10H 8) (DME) and Cp *Lu(C 10H 8) (DME) in toluene. Both complexes are paramagnetic (μ eff = 1.4 and 0.9 BM) and exhibit temperature-dependent ESR signals (293 K: g = 1.992 and 2.0002 respectively). 相似文献
5.
用5种实验方法对东北草原区233种植物光合类型进行鉴定,并对其相对分布随纬度变化关系及其与土壤含盐量和PH值的关系进行分析.在此基础上对几种典型C 3、C 4牧草适应于盐碱环境的生理特点进行深入研究结果表明,在所鉴定的233种植物中,C 3植物有144种,隶属于28科94属,C 4植物有89种;隶属于17科55属,在高纬度地区C 3植物表现出更高的生长优势,在纬度较低和盐碱化区域,C 4植物分布具相对优势.尤其在盐碱化程度较重的地区,C 4植物成为明显的优势种,分布上的差别决定于它们对环境适应机制上的差异C 3植物对盐碱环境适应机制主要通过积累脯氨酸等有机溶质进行渗透调节,而C 4植物主要通过液泡中离子区域化积累作用进行调节,并且与C 3植物相比对盐碱环境具更强的适应能力. 相似文献
6.
The characteristic surface lipid compositions of several C 3 and C 4 plants are discussed. C 4 plants produce surface lipids (epicuticular waxes) made up of the ubiquitous classes of aliphatic compounds: free fatty acids, aldehydes, primary alcohols, alkanes and aliphatic linear esters. C 3 plants synthesize surface lipids comprising the ubiquitous classes and either of the two following groups of compound: (i) lβ-diketones, hydroxy lβ-diketones, alkan-2-ol esters; (il) ketones and secondary alcohols with the functional group in the middle of the hydrocarbon chain. These features are suggested to represent physioIogical characteristics of the plant and to be related to ecological adaptations. Wax class compositions might also be an ancillary method for defining the C 3 or C 4 mechanism of CO 2 assimilation in cases where uncertainty exists. 相似文献
7.
The North American tallgrass prairie is composed of a diverse mix of C 3 and C 4 plant species that are subject to multiple resource limitations. C 4 grasses dominate this ecosystem, purportedly due to greater photosynthetic capacity and resource-use efficiency associated with C 4 photosynthesis. We tested the hypothesis that intrinsic physiological differences between C 3 and C 4 species are consistent with C 4 grass dominance by comparing leaf gas exchange and chlorophyll fluorescence variables for seven C 4 and C 3 herbaceous species (legumes and non-legumes) in two different settings: experimental mesocosms and natural grassland sites. In the mesocosms, C 4 grasses had higher photosynthetic rates, water potentials and water-use efficiency than the C 3 species. These differences were absent in the field, where photosynthetic rates declined similarly among non-leguminous species. Thus, intrinsic photosynthetic advantages for C 4 species measured in resource-rich mesocosms could not explain the dominance of C 4 species in the field. Instead, C 4 dominance in this ecosystem may depend more on the ability of the grasses to grow rapidly when resources are plentiful and to tolerate multiple limitations when resources are scarce. 相似文献
8.
We have integrated two cDNAs expressing Sorghum photosynthetic phosphoenolpyruvate carboxylase (C 4-PEPC) and NADP-malate dehydrogenase (cpMDH), two key enzymes involved in the primary carbon fixation pathway of NADP-malic enzyme-type C 4 plants, separately or together into a C 3 plant (potato). Analysis of the transgenic plants showed a 1.5-fold increase in PEPC and cpMDH activities compared to untransformed plants. Immunolocalization confirmed an increase at the protein level of these two enzymes in the transgenic plants and indicated that the Sorghum cpMDH was specifically addressed to the chloroplasts of potato mesophyll cells. However, integration of either or both of the cDNAs into the potato genome did not appear to significantly modify either tuber starch grain content or the rate of photosynthetic O 2 production compared to control untransformed plants. The low level of transgene expression probably explains the lack of influence on carbon metabolism and photosynthetic rates. This general observation suggests that some complex mechanism may regulate the level of production of foreign C 4 metabolism enzymes in C 3 plants. 相似文献
9.
Reactions of [Rh(COD)Cl] 2 with the ligand RN(PX 2) 2 (1: R = C 6H 5; X = OC 6H 5) give mono- or disubstituted complexes of the type [Rh 2(COD)Cl 2{ν 2−C 6H 5N(P(OC 6H 5) 2) 2}] or [RhCl{ν 2−C 6H 5 N(P(OC 6H 5) 2) 2 }] 2 depending on the reaction conditions. Reaction of 1 with [Rh(CO) 2Cl] 2 gives the symmetric binuclear complex, [Rh(CO)Cl{μ−C 6H 5N(P(OC 6H 5) 2) 2} 2, whereas the same reaction with 2 (R = CH 3; X = OC 6H 5) leads to the formation of an asymmetric complex of the type [Rh(CO)(μ−CO)Cl{μ−CH 3N(P(OC 6H 5) 2) 2} 2 containing both terminal and bridging CO groups. Interestingly the reaction of 3 (R = C 6H 5, X = OC 6H 4Br− p with either [Rh(COD)Cl] 2 or [Rh(CO) 2Cl] 2 leads only to the formation of the chlorine bridged binuclear complex, [RhCl{ν 2−C 6H 5N(P(OC 6H 4Br− p) 2) 2}] 2. The structural elucidation of the complexes was carried out by elemental analyses, IR and 31P NMR spectroscopic data. 相似文献
10.
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
11.
The loess/paleosol sequence in loess layer L1 (Malan Loess) is investigated in three regions of the Western Chinese Loess Plateau. Nine pedogenic layers are found in L1 and three proxy climate indices, magnetic susceptibility (MS), grain size (GS) and CaCO 3 content, are measured at intervals of 0.2 kyr in order to recover records of monsoon climate variations. Time series of MS, GS and CaCO 3 content document the high resolution history of summer and winter monsoon climate variations over the last 75 kyr. The records show a high degree of similarity to the warm interstadials recorded in ice cores from Greenland and the Antarctic, and with Heinrich events in the North Atlantic, during the last glacial cycle. Bond cycles are also recorded by the Chinese loess records. Overall, our results indicate that numerous rapid changes in climate occurred in China during the last glacial cycle, but that the range of climate variations was smaller than recorded in Greenland. 相似文献
12.
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
13.
The effects of a novel leukotriene (LT) C 4/D 4 antagonist, BAY-x-7195 on experimental allergic reactions in airway and skin were compared to that of ONO-1078. BAY-x-7195 showed an antagonistic action to LTD 4-induced bronchoconstriction in vitro and in vivo. In in vitro experiments, BAY-x-7195 inhibited LTD 4-induced contraction of isolated guinea pig tracheal muscle (pA2=8.03). BAY-x-7195 at doses of 3 – 30 mg/kg clearly inhibited LTD 4-induced increases in respiratory resistance (Rrs) in guinea pigs. In contrast, BAY-x-7195 inhibited significantly U-46619-induced increases in Rrs at a dose of 30 mg/kg in guinea pigs. BAY-x-7195 at doses of 3 — 30 mg/kg inhibited the aerosolized antigen-induced biphasic increase in Rrs in guinea pigs. Moreover BAY-x-7195 inhibited repeated aeroantigen-induced airway hyperreactivity in guinea pigs. In mice, aeroantigen-induced airway inflammation were clearly inhibited by BAY-x-7195. These results show the efficacy of BAY-x-7195 against the antigen-induced increase in airway resistance and antigen-induced airway hyperreactivity in guinea pigs and mice, probably due to anti-LTD 4 antagonistic action and the inhibition of antigen-induced airway inflammation. 相似文献
14.
植物种内变异对草地表层有机质碳同位素组成预测C 3/C 4植被比的影响植物群落中C 3和C 4植物的比例和组成对诸多生态系统过程具有重要影响。解析C 3和C 4植物碳同位素的环境驱动过程与调控因子,对于从土壤碳同位素的角度来预测C 3/C 4植被比和组成具有重要意义。本研究旨在评估草原植物碳同位素特征的种内变异将如何影响C 3和C 4植物的碳同位素组成以及C 3/C 4植被比的预测。沿中国北方草原的自然干旱梯度选择26个植物群落,通过分析植物和土壤的碳同位素组成,采用混合模型来预测C 4植物对土壤有机碳的相对贡献。本研究对比分析了如下3种情境:(1)考虑C 3和C 4植物碳同位素的种内和种间效应;(2)仅考虑碳同位素的种间变异;(3)忽略碳同位素的种内和种间变异。研究结果表明,植物碳同位素组成沿中国北方草原自然干旱梯度的变化具有物种特异性。C 3和C 4植物的碳同位素组成与干旱指数之间呈显著负相关关系,但C 3植物比C 4植物对环境的干旱变化更为敏感。植物碳同位素特征的种内变异在驱动C 3植物功能群碳同位素沿干旱梯度的分布格局中发挥着重要作用。如果忽略植物碳同位素特征的种内变异将会显著高估C 4植物的相对贡献。本研究结果表明,草原植物碳同位素特征的种内变异对于准确预测C 3/C 4植被组成具有重要意义。 相似文献
15.
Following a series of continuous exposures to 14CO 2 for different lengths of time, leaves from Neurachne munroi (C 4), N. minor (C 3-C 4) and N. tenuifolia (C 3| were estimated to assimilate 100%, 9% and 2–4%, respectively, of atmospheric CO 2 by the C 4 pathway. The percentage of 14C-label appearing in malate and aspartate in leaves of N. minor progressively increased with longer exposure times indicating that a significant proportion of its C 4 acids are formed as secondary products. In 14CO 2/ 12CO 2 pulse/chase experiments, the 14C-label in leaves of N. munroi was rapidly transferred from C 4 acids to sugar monophosphates plus sugar diphosphates, and finally to sucrose. In leaves of N. minor, the 14C-label was slowly metabolized from the C-4 carboxyl of malate and asparate (apparent half-time = 250 s), and the formation of C 4 acids as secondary products was again evident. 14C-label in serine/glycine accumulated to comparable magnitudes in both N. minor and in N. tenuifolia, but there was an initial lag phase in the accumulation of label in N. minor. C 4 photosynthesis is apparently of minimal importance in reducing photorespiration in N. minor, but leaf anatomical specializations and a possible compartmentation of photorespiratory metabolism may be of considerable importance. 相似文献
16.
The amino-functionalized metallocene (C 5H 4CH(Me)NMe 2) 2ZrCl 2, [(Cp N) 2ZrCl 2] was synthesized by salt metathesis of ZrCl 4 and 2 equiv. of C 5H 4CH(Me)NMe 2Li. The metallocene was obtained in good yield as a mixture of rac and meso diastereomers as established by NMR spectroscopy. The addition of 2 equiv. of n-BuLi to the metallocene (Cp N) 2ZrCl 2 produced a co-catalyst system which was active, at a 1.0 mol% loading, in the dehydropolymerization of PhSiH 3 to poly(phenylsilane), PPSi. The PPSi was obtained as a 9:1 linear–cyclic mixture ( Mw=3850, Mn=2300) as established by GPC analysis; 29Si{ 1H} NMR spectroscopy revealed an atactic polymer microstructure. 相似文献
17.
The aqueous chemistry of vanadium with physiologically relevant ligands constitutes a subject of burgeoning research, extending from bacterial metalloenzymic functions to human-health physiology. Vanadium, in the form of VCl 3 and V 2O 5, reacted expediently with citric acid, in a 1:2 molar ratio in water at pH4, and, in the presence of various cations, afforded crystalline materials bearing the general formula (Cat) 2[V 2O 4(C 6H 6O 7) 2]· nH 2O (A) (Cat +=Na +, NH 4 +, n=2; Me 4N +, K +, n=4). Exploration of the reactivity of A toward H 2O 2 yielded the peroxo-containing complexes (Cat) 2[V 2O 2(O 2) 2(C 6H 6O 7) 2]·2H 2O (B) (Cat +=K +, NH 4 +). Both classes of compounds were characterized analytically and spectroscopically. The X-ray structures of complexes A and B emphasize the exceptional stability of the dimeric rhombic unit V V 2O 2, which is retained upon H 2O 2 reaction, and the preserved mode of coordination of the citrate ligand as a doubly deprotonated moiety. In these complexes, typical six and eight coordination numbers were observed for the Na + and K + counter-ions, respectively. The variety of synthetic approaches leading to A, along with the stepwise and direct assembly and isolation of peroxo-compounds (B), denotes the significance of reaction pathways and intermediates in vanadium(III–V)–citrate synthetic chemistry. Hence, a systematic investigation of reactivity modes in aqueous vanadium–citrate systems emerges as a crucial tool for the establishment of chemical interconnectivity among low MW complex species, potentially participating in the intricate biodistribution of that metal ion in biological fluids. 相似文献
18.
The binuclear cyanoferrate, tetraphenylphosphonium pentacyanoiron(III)-μ-cyano-amminetetracyanoiron(III), [(C 6H 5) 4P] 4[Fe 2(CN) 10NH 3] 4−, was synthesized by air oxidation of aqueous solutions of Na 3[Fe(CN) 5NH 3] · 3H 2O. Single crystal X-ray diffraction studies show the compound to contain the binuclear, cyano-bridged anion, [(NC) 5Fe---NC---Fe(CN) 4NH 3] 4−. This compound is structurally identical to the one prepared by A. Ludi et al., [Inorg. Chim. Acta, 34, 113 (1979)], with the exception that [Fe(CN) 6] 3− is not required for the synthesis of this compound. The Fe(III) atoms are antiferromagnetically coupled through the CN − bridge, as shown by a maximum in the magnetic susceptibility at 50 K. The electronic and IR spectra of the complex in the solid state and in solution are discussed. 相似文献
19.
1. Cyclic photophosphorylation driven by white light, as followed by 14CO 2 fixation by mesophyll chloroplast preparations of the C 4 plant Digitaria sanguinalis, was specifically inhibited by disalicylidenepropanediamine (DSPD), antimycin A, 2,5-dibromo-3-methyl-6-isopropyl- p-benzoquinone (DBMIb), 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide (EDAC), and KCN suggesting that ferredoxin, cytochrome b563, plastoquinone, cytochrome f, and plastocyanin are obligatory intermediates of cyclic electron flow. It was found that 0.2 μM DCMU and 40 μM o-phenanthroline blocked noncyclic electron flow, stimulated cyclic photophosphorylation, and caused a partial reversal (40–100%) of the inhibition by DBMIB and antimycin A, but not DSPD. 2. Cyclic photophosphorylation could also be activated using only far-red illumination. Under this condition, however, cyclic photophosphorylation was much less sensitive to the inhibitors DBMIB, EDAC and antimycin A, but remained completely sensitive to DSPD and KCN. Inhibition in far-red light was not increased by preincubating the chloroplasts with the various inhibitors for several minutes in white light. 3. The striking correspondence between the effects of photosystem II inhibitors, DCMU and o-phenanthroline, on cyclic photophosphorylation under white light and cyclic photophosphorylation under far-red light (in the absence of photosystem II inhibitors) suggests that electrons flowing from photosystem II may regulate the pathway of cyclic electron flow. 相似文献
20.
The reactions of the polysulfur and selenium cationic clusters S 82+ and Se 82+ with various iron carbonyls were investigated. Several new chalcogen containing iron carbonyl cluster cations were isolated, depending on the nature of the counteranion. In the presence of SbF 6− as a counterion, the cluster [Fe 3(E 2) 2(CO) 10] [SbF 6] 2·SO 2 (E = S, Se) could be isolated from the reaction of E 82+ and excess iron carbonyl. The cluster is a picnic-basket shaped molecule of two iron centers linked by two Se 2 groups, with the whole fragment capped by an Fe(CO) 4 group. Crystallographic data for C 10O 12Fe 3Se 4Sb 2F 12S (I): space group monoclinic P2 1/ c, A = 11.810(9), b = 24.023(6), c = 10.853(7) Å, β = 107.15(5)°, V = 2942(3) Å 3, Z = 4, R = 0.0426, Rw = 0.0503. When Sb 2F 11− is present as the counterion, or Se 4[Sb 2F 11] 2 is used as the cluster cation source, a different cluster can be isolated, which has the formula [Fe 4(Se 2) 3(CO) 12] [SbF 6] 2·3SO 2. The dication contains two Fe 2Se 2 fragments bridged by an Se 2 group. Crystallographic data for C 12O 18Fe 4Se 6Sb 2F 12S 3 (III): space group triclinic
, b = 18.400(9), C = 10.253(4) Å, = 93.10(4), β = 103.74(3), γ = 93.98(3)°, V = 1995(1) Å 3, Z = 2, R = 0.0328, Rw = 0.0325. The CO stretches in the IR spectrum all show a large shift to higher wavenumbers, suggesting almost no τ backbonding from the metals. This also correlates with the observed bond distances. All the compounds are extremely sensitive to air and water, and readily lose SO 2 when removed from the solvent. Thus all the crystals were handled at −100°C. The clusters seem to be either insoluble or unstable in all solvents investigated. 相似文献
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