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1.
Tetraphenylantimony(V) O,O′-di-sec-butyl dithiophosphate (I) and tetraphenylantimony(V) O,O′-dicyclohexyl dithiophosphate (II) [Sb(C6H5)4{S2P(OR)2}] (R = sec-C4H9 or cyclo-C6H11) were obtained. Their structures and spectroscopic properties were studied by X-ray diffraction analysis and 13C and 31P CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in complexes I and II were found to be coordinated in S-monodentate and S,S′-bidentate fashions, respectively (MAS NMR data). According to X-ray diffraction data, the coordination polyhedron of antimony in molecular structure I is a trigonal bipyramid with unusual monodentate coordination of the Dtph group in the axial position.  相似文献   

2.
Visible light irradiation of the dicarbollide complex [(η-9-SMe2-7,8-C2B9H10)Fe(η-C6H6)]+ (2a) in the presence of the benzene derivatives in CH2Cl2/MeNO2 resulted in cations [(η-9-SMe2-7,8-C2B9H10)Fe(η-C6R6)]+ (2b-g; arene is anisole (b), toluene (c), m-xylene (d), mesitylene (e), durene (f), and hexamethylbenzene (g)) due to the arene exchange. The structures of [2g]PF6 and related tricarbollide complex [(η-1-ButNH-1,7,9-C3B8H10)Fe-(η-C6H6)]PF6 (1) were confirmed by X-ray diffraction analysis. The nature of bonding in cations 1, 2a, and [CpFe(η-C6H6)]+ was analyzed by an energy decomposition analysis.  相似文献   

3.
The reactions of [Ru3(CO)10(μ-dppm)] 4 with quinolines afforded [Ru3 (μ-CO)(CO)732-P(C6H5)CH2P(C6H5)2)}{μ-η2-C9H5(R)N}] (8, R = 4-Me; 9, R = H) as the major products along with small amounts of known compound [Ru3(CO)933-P(C6H5)CH2P(C6H5)(C6H4)}] 5. The molecular structure of 8 has been determined by single crystal X-ray studies. The reaction of 5 with 4-methylquinoline in refluxing cyclohexane afforded 8 and two known dinuclear compounds, [Ru2(CO)6{μ-CH2P(C6H5)(C6H4)P(C6H5}] 10 and [Ru2(CO)6 {μ-(C6H4)P(C6H5)(CH2)P(C6H5}] 11, in 40, 12, and 10% yields, respectively. The compounds 10 and 11 are also formed from the thermolysis of 4 in addition to the major compound 5. The solid state structure of the previously reported [Ru3(CO)10(η-H){μ-η2-C9H6N}] 2a is also reported for comparison.  相似文献   

4.
Thermolysis of [Ru3(CO)12] in cyclohexene for 24 h affords the complexes [Ru(CO)34-C6H8)] (1), [Ru3H2(CO)92121-C6H8)] (2), [Ru4(CO)124-C6H8)] (3) [Ru4(CO)94-C6H8)(η6-C6H6)] (4a and 4b, two isomers) and [Ru5(CO)1242-C6H8)(η4-C6H8)] (5), where 1, 3, 4a and 4b have been previously characterised as products of the thermolysis of [Ru3(CO)12] with cyclohexa-1,3-diene. The molecular structures of the new clusters 2 and 5 were determined by single-crystal X-ray crystallography, showing that two conformational polymorphs of 5 exist in the solid state, differing in the orientation of the cyclohexa-1,3-diene ligand on a ruthenium vertex.  相似文献   

5.
Photoionization mass spectrometry was used to investigate the dynamics of ion-neutral complex-mediated dissociations of the n-pentane ion (1). Reinterpretation of previous data demonstrates that a fraction of ions 1 isomerizes to the 2-methylbutane ion (2) through the complex CH3CH+CH 3 · CH2CH3 (3), but not through CH3CH+CH2CH 3 · CH3 (4). The appearance energy for C3Hin 7 + formation from 1 is 66 kJ mol?1 below that expected for the formation of n-C3H 7 + and just above that expected for formation of i-C3H 7 + . This demonstrates that the H shift that isomerizes C3H 7 + is synchronized with bond cleavage at the threshold for dissociation to that product. It is suggested that ions that contain n-alkyl chains generally dissociate directly to more stable rearranged carbenium ions. Ethane elimination from 3 is estimated to be about seven times more frequent than is C-C bond formation between the partners in that complex to form 2, which demonstrates a substantial preference in 3 for H abstraction over C-C bond formation. In 1 → CH3CH+CH2CH3 + CH3 by direct cleavage of the C1–C2 bond, the fragments part rapidly enough to prevent any reaction between them. However, 1 → 2 → 4 → C4H 8 + + CH4 occurs in this same energy range. Thus some of the potential energy made available by the isomerization of n-C4H9 in 1 is specifically channeled into the coordinate for dissociation. In contrast, analogous formation of 3 by 1 → 3 is predominantly followed by reaction between the electrostatically bound partners.  相似文献   

6.
The synthesis and characterization of novel amidoamine-based metallodendrimers with heterobimetallic end-grafted amidoferrocenyl-palladium-allyl chloride units is described. Dendrimer (Fe((η5-C5H4PPh2)(η5-C5H4))C(O)HNCH2CH2NHC(O)CH2CH2)N[CH2CH2N(CH2CH2C(O)NHCH2CH2NH-C(O)(Fe(η5-C5H4)(η5-C5H4PPh2)))2]2 (9-Fe) and the corresponding metal species (Fe((η5-C5H4PPh2(Pd(η3-C3H5)Cl))(η5-C5H4))C(O)HNCH2CH2NHC(O)CH2CH2)N[CH2CH2N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(η5-C5H4)(η5-C5H4PPh2(Pd(η3-C3H5)Cl))))2]2 (9-Fe-Pd) were prepared by a consecutive divergent synthesis methodology including addition-amidation cycles, standard peptide coupling, and coordination procedures. For comparative reasons also the monomeric and dimeric molecules (Fe(η5-C5H4PPh2)(η5-C5H4C(O)NHnC3H7)) (5-Fe) and [Fe(η5-C5H4PPh2)(η5-C5H4C(O)NHCH2)]2 (6-Fe) as well as N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(η5-C5H4)(η5-C5H4PPh2)))3 (7-Fe) and [CH2N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(η5-C5H4)(η5-C5H4PPh2)))2]2 (8-Fe) were prepared from Fe(η5-C5H4PPh2)(η5-C5H4CO2H) (3). Using [Pd(η3-C3H5)Cl]2 (4) as palladium source heterobimetallic metallodendrimers (Fe(η5-C5H4PPh2(Pd(η3-C3H5)Cl))(η5-C5H4C(O)NHnC3H7)) (5-Fe-Pd), [Fe(η5-C5H4PPh2(Pd(η3-C3H5)Cl))(η5-C5H4C(O)NHCH2)]2 (6-Fe-Pd), N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(η5-C5H4)(η5-C5H4PPh2(Pd(η3-C3H5)Cl))))3 (7-Fe-Pd) and [CH2N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(η5-C5H4)(η5-C5H4PPh2(Pd(η3-C3H5)Cl))))2]2 (8-Fe-Pd) were synthesized. Additionally, seleno-phosphines of 5-Fe-Se and 9-Fe-Se, respectively, were prepared by addition of elemental selenium to 5-Fe or 9-Fe to estimate their σ-donor properties.The palladium-containing amidoamine supports are catalytically active in the Heck-Mizoroki cross-coupling of iodobenzene with tert-butyl acrylate. The catalytic data are compared to those obtained for the appropriate mononuclear and dinuclear compounds 5-Fe-Pd and 6-Fe-Pd. This comparison confirms a positive cooperative effect. The mercury drop test showed that (nano)particles were formed during catalysis, following on heterogeneous carbon-carbon cross-coupling.  相似文献   

7.
The acid-mediated reaction of [{Co2(CO)6(μ-η2-HOCH2CC-)}2] (1) with the meta- and para-substituted aminothiophenols, 3-NH2-C6H4SH and 4-NH2-C6H4SH, affords the straight chain species, [{Co2(CO)6(μ-η2-(3-NH2-C6H4S)CH2CC-)}2] (2) and [{Co2(CO)6(μ-η2-(4-NH2-C6H4S)CH2CC-)}2] (3), respectively. The molecular structure of 3 reveals the presence of two isomeric forms differing in the relative disposition of the S-aryl groups. Conversely, reaction of 1 with the ortho-substituted aminothiophenol, 2-NH2-C6H4SH, furnishes the 10-membered macrocyclic species [{Co2(CO)6}2{cyclo-μ-η2:μ-η2-CH2C2C2CH2SC6H3-NH-2}] (4) along with the linear chain complex [{Co2(CO)6(μ-η2-(2-NH2-C6H4S)CH2CC-)}2] (5). On the other hand, treatment of 1 with the ortho-substituted mercaptopyridine, 2-SH-C5H4N, in the presence of HBF4 gives the salt [{Co2(CO)6(μ-η2-(2-S-C5H4NH)CH2CC-)}2](BF4)2 (6a) in good yield; work-up in the presence of base affords the neutral complex [{Co2(CO)6(μ-η2-(2-S-C5H4N)CH2CC-)}2] (6b). Single crystal X-ray diffraction studies have been reported on 3-5 and 6a.  相似文献   

8.
The complex trans-[RuPy4(CN)2] cleaves chloride bridges in the binuclear rhodium(i) and palladium(ii) complexes [Rh(CO)2Cl]2, [Rh(η4-C8H12)Cl]2, [(η4-C8H12)Rh(μ-Cl)2Rh(CO)2], [Pd(η3-C3H5)Cl]2, and [(η3-C3H5)Pd(μ-Cl)2Rh(CO)2] to form heterometallic triad complexes [(CO)2ClRh(NC)RuPy4(CN)RhCl(CO)2] (1), [(η4-C8H12)ClRh(NC)RuPy4(CN)RhCl-(η4-C8H12)] (2), [(CO)2ClRh(NC)RuPy4(CN)RhCl(η4-C8H12)] (3), [(η3-C3H5)ClPd(NC)-Ru(Py)4(CN)PdCl(η3-C3H5)] (4), and [(CO)2ClRh(NC)Ru(Py)4(CN)PdCl(η3-C3H5)] (5), respectively. In solutions, complex 3 coexists with equilibrium amounts of compounds 1 and 2; complex 5 is in the equilibrium with compounds 4 and 1. In both cases, the ratio of concentrations is close to binomial. Complexes 2 and 5 treated with [Rh(CO)2Cl]2 are converted into 1 with the simultaneous formation of [Rh(η4-C8H12)Cl]2 and [Pd(η3-C3H5)Cl]2, respectively. The δH and δC values for the ligands η4-C8H12, η3-C3H5, and CO are sensitive to the nature of the remote triad unit. The ligand effects are shown to be transmitted along the chain L′-M′-(NC)-Ru-(CN)-M″-L″.  相似文献   

9.
Multiple stage MS2 and MS3 mass spectrometric experiments, performed using a pentaquadrupole instrument, are employed to explore the gas-phase ion-molecule chemistry of several nitrilium [R-C≡N+-H (1), R-C≡N+-CH3 (2), and H-C≡N+-C2H5 (3)] as well as immonium ions RR1C=N+R2R3 (4) with the neutral diene isoprene. Polar [4+2+] Diels-Alder cycloaddition is observed for nitrilium ions when the energy gap between the lowest unoccupied molecular orbital (LUMO) of the ion and the highest occupied molecular orbital (HOMO) of the isoprene is small and the competing proton transfer reaction is endothermic. Thus, C-protonated methyl isonitrile H-C≡N+-CH3 (2a) and its higher homolog H-C≡N+-C2H5 (3a) form abundant [4+2+] cycloadducts with isoprene, but several protonated nitriles 1 do not; instead they show exothermic proton transfer as the main ion-molecule reaction. Replacement of the methyne hydrogen in 2a by a methyl, ethyl, or phenyl group (2b–d) raises the LUMO-HOMO gap, which greatly decreases the total yield of ion-molecule products and precludes cycloaddition. On the other hand, the electron-withdrawing acetyl and bromine substituents in 2e and 2f substantially lower the LUMO energy of the ions and cycloaddition reaction occurs readily. The simplest member of the immonium ion series, CH2=NH 2 + (4a), reacts readily by cycloaddition, whereas alkyl substitution on either the carbon or nitrogen (4b–f) dramatically lowers the overall reactivity, which substantially decreases or even precludes cycloaddition. In strong contrast, the N-phenyl (4g) and N-acetyl (4h) ions and the N-vinyl-substituted immonium ion, N-protonated 2-aza-butadiene (4i), react extensively with isoprene, mainly by [4+2+] cycloaddition. However, the isomeric C-vinyl-substituted ion (4j) displays only modest reactivity in both the proton-transfer and the cycloaddition channels. Collision-induced dissociation (CID) of the cycloadducts performed by on-line MS3 experiments demonstrates that they are covalently bound and supports their assignments as cycloaddition products. Retro Diels-Alder fragmentation is a major process for cycloadducts of both the immonium and the nitrilium ions, but other fragmentation processes also are observed. The cycloadduct of 4a with butadiene displays CID fragmentation identical to that of the authentic ion produced by protonation of 1,2,3,6-tetrahydropyridine, which thus strengthens the [4+2+] cycloaddition proposal. AM1 calculations also support the formation of the [4+2+] cycloadducts, which are shown in several cases to be much more stable than the products of simple addition, that is, the ring-open isomers.  相似文献   

10.
Reaction of [VO(OPr i )3] (1) with [O(CH2CH2OH)2] in 1:1 molar ratio in anhydrous benzene yield glycol-modified precursor, [VO{OCH2CH2OCH2CH2O}{OPr i }] (2). Further reactions of (2) with internally functionalized oximes in anhydrous benzene yield heteroleptic complexes of the type [VO{OCH2CH2OCH2CH2O}{ON=C(R)(Ar)}] (3–8) {where R=CH3, Ar=C4H3O-2 (3), C4H3S-2 (4), C5H4N-2 (5); and when R=H, Ar=C4H3O-2 (6), C4H3S-2 (7), C5H4N-2 (8)}. All these derivatives have been characterized by elemental analyses, molecular weight measurements and spectroscopic techniques. The crysoscopic molecular weight measurement as well as FAB mass study suggests dimeric nature of (2). However, FAB mass spectrum of (4), and the crysoscopic molecular weight measurements of (3), (4), (5) and (6) indicate the monomeric behavior of the oximato derivatives (3–8). Hexa-coordination around vanadium(V) has been proposed for both monomeric and dimeric derivatives. Sol–gel transformations of (1), (2) or (4) to vanadia [(a), (b) or (c), respectively] have been carried out at low sintering temperature (600 °C). The XRD patterns of (a), (b) or (c) indicate formation of a single orthorhombic phase in all the three cases. The SEM images suggest grain like [for (a) and (b)] and rod like [for (c)] morphology of the crystallites. IR, Raman spectra as well as EDX analyses indicate formation of pure vanadia. Absorption spectra of the vanadia (b) and (c) suggest energy band gaps of 2.53 and 2.65 eV, respectively.  相似文献   

11.
Cationic complexes [(diene)Co(??-C6Me6)]+ (diene is buta-1,3-diene (2a), 5-isopropyl-2-methylcyclohexa-1,3-diene (2b), cycloocta-1,3-diene (2c), and cyclohexa-1,5-diene (2d)) were synthesized by the reaction of [Co(??-C6Me6)2]+ (1) with dienes in a CH2Cl2-Me2CO mixture. In the absence of dienes, cation 1 undergoes hydrogenation to form [(1,2,3,4,5,6-HMCD-1,3)-Co(??-C6Me6)]+ (HMCD is hexamethylcyclohexadiene, 2e). Structures [2c?Ce]PF6 were determined by X-ray diffraction analysis. According to the DFT calculations, the Co-C6H6 bond in the complexes with conjugated dienes is stronger than that in the complexes with nonconjugated dienes.  相似文献   

12.
The alkenyl-substituted titanocene complex [Ti(η5-C5H5)(η5-C5H4{CMe2(CH2CH2CHCH2)})Cl2] (1) has been synthesized and characterized using traditional methods. The reaction of 1 with 9-BBN gave the boryl substituted complex [Ti(η5-C5H5)(η5-C5H4{CMe2(CH2CH2CH2CH2BC8H14)})Cl2] (2). The cytotoxic activity of 1 and 2 was tested against tumour cell lines human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x, human breast carcinoma MDA-MB-361 and normal immunocompetent cells peripheral blood mononuclear cells PBMC and compared with those of the reference complexes [Ti(η5-C5H5)2Cl2] (R1), [Ti(η5-C5H4Me)2Cl2] (R2) and [Ti(η5-C5H5)(η5-C5H4SiMe3)Cl2] (R3). Complex 1 showed higher cytotoxic activities on HeLa, Fem-x and K562 (IC50 values from 96.6 ± 3.4 to 149.2 ± 2.9 μM) than the reference complexes R1, R2 and R3 which presented IC50 values from 173.3 ± 6.0 to >200 μM. On the other hand, boryl substituted complex 2, present slightly lower cytotoxic activities than 1 on HeLa, Fem-x and K562 (IC50 values from 155.6 ± 5.5 to 167.9 ± 4.2 μM). However, 2 was the most active of the studied complexes against MDA-MB-361 (IC50 value of 161.1 ± 0.1 μM). Structural studies based on DFT calculations of 1 and 2 have also been carried out in order to gain a possible insight into the relationship between metal complex structure and cytotoxicity.  相似文献   

13.
Eight ionic organotin compounds [R2SnCl2(2-quin)](HNEt3)+ have been synthesized by reactions of 2-quinH with R2SnCl2 (R = PhCH21, 2-Cl-C6H4CH22, 4-Cl-C6H4CH23, 2-F-C6H4CH24, 4-F-C6H4CH25, 4-CN-C6H4CH26, Ph 7, 2,4-Cl2-C6H3CH28) in the presence of organic base NEt3, and their structures have been characterized by elemental analysis, IR and multinuclear NMR (1H, 13C, 119Sn) spectroscopies. The structure of [(2,4-Cl2-C6H3CH2)2SnCl2(2-quin)](NEt3)+ (8) has been determined by X-ray diffraction study. Studies show that compound 8 has a monomeric structure with the central tin atom six-coordinate in a distorted octahedral configuration and the nitrogen atoms of the 2-quin ligands are coordinating to the tin atom in all the eight compounds.  相似文献   

14.
The complex [(η6-p-cymene)Ru(μ-Cl)Cl]21 reacts with pyrazole ligands (3a-g) in acetonitrile to afford the amidine derivatives of the type [(η6-p-cymene)Ru(L)(3,5-HRR′pz)](BF4)2 (4a-f), where L = {HNC(Me)3,5-RR′pz}; R, R′ = H (4a); H, CH3 (4b); C6H5 (4c); CH3, C6H5 (4d) OCH3 (4e); and OC2H5 (4f), respectively. The ligand L is generated in situ through the condensation of 3,5-HRR′pz with acetonitrile under the influence of [(η6-p-cymene)RuCl2]2. The complex [(η6-C6Me6)Ru(μ-Cl)Cl]22 reacts with pyrazole ligands in acetonitrile to yield bis-pyrazole derivatives such as [(η6-C6Me6)Ru (3,5-HRR′pz)2Cl](BF4) (5a-b), where R, R′ = H (5a); H, CH3 (5b), as well as dimeric complexes of pyrazole substituted chloro bridged derivatives [{(η6-C6Me6)Ru(μ-Cl) (3,5-HRR′pz)}2](BF4)2 (5c-g), where R, R′ = CH3 (5c); C6H5 (5d); CH3, C6H5 (5e); OCH3 (5f); and OC2H5 (5g), respectively. These complexes were characterized by FT-IR and FT-NMR spectroscopy as well as analytical data. The molecular structures1 of representative complexes [(η6-C6Me6)Ru{3(5)-Hmpz}2Cl]+5b, [(η6-C6Me6)Ru(μ-Cl)(3,5-Hdmpz)]22+5c and [(η6-C6Me6)Ru(μ-Cl){3(5)Me,5(3)Ph-Hpz}]22+5e were established by single crystal X-ray diffraction studies.  相似文献   

15.
Kai-Min Wu 《Tetrahedron》2005,61(41):9679-9687
Three pendant benzamidines [Ph-C(NC6H5)-{NH(CH2)2NMe2}] (1), [Ph-C(NC6H5)-{NH(CH2Py)}] (2) and [Ph-C(NC6H5)-{NH(o-C6H4)(oxazoline)}] (3) are described. Reactions of 1, 2 or 3 with one molar equivalent of Pd(OAc)2 in THF give the palladacyclic complexes [Ph-C{-NH(η1-C6H4)}{N(CH2)2NMe2}]Pd(OAc) (4), [Ph-C{-NH(η1-C6H4)}{N (CH2Py)}]Pd(OAc) (5) and [Ph-C{-NH(η1-C6H4)}{N(o-C6H4)(oxazoline)}]Pd(OAc) (6), respectively. Treatment of 4, 5 or 6 with excess of LiCl in chloroform affords [Ph-C{-NH(η1-C6H4)}{N(CH2)2NMe2}]PdCl (7), [Ph-C{-NH(η1-C6H4)}{N(CH2Py)}]PdCl (8) and [Ph-C{-NH(η1-C6H4)}{N(o-C6H4)(oxazoline)}]PdCl (9). The crystal and molecular structures are reported for compounds 1, 3, 5, 6 and 7. The application of these palladacyclic complexes to the Suzuki and Heck coupling reactions was examined.  相似文献   

16.
Eleven isomers with the PyC2H 5 composition, which include three conventional (1–3) and eight distonic radical cations (4–11), have been generated and in most cases successfully characterized in the gas phase via tandem-in-space multiple-stage pentaquadrupole MS2 and MS3 experiments. The three conventional radical cations, that is, the ionized ethylpyridines C2H5-C5H4N (1–3), were generated via direct 70-eV electron ionization of the neutrals, whereas sequences of chemical ionization and collision-induced dissociation (CID) or mass-selected ion-molecule reactions were used to generate the distonic ions H2C·?C5H4N+?CH3 (4–6), CH3?C5H4N+?CH 2 · (7–9), C5H5N+?CH2CH 2 · (10), and C5H5N+?CH·?CH3 (11). Unique features of the low-energy (15-eV) CID and ion-molecule reaction chemistry with the diradical oxygen molecule of the isomers were used for their structural characterization. All the ion-molecule reaction products of a mass-selected ion, each associated with its corresponding CID fragments, were collected in a single three-dimensional mass spectrum. Ab initio calculations at the ROMP2/6–31G(d, p)//6–31G(d, p)+ZPE level of theory were performed to estimate the energetics involved in interconversions within the PyC2H5 system, which provided theoretical support for facile 4?7 interconversion evidenced in both CID and ion-molecule reaction experiments. The ab initio spin densities for the a-distonic ions 4–9 and 11 were found to be largely on the methylene or methyne formal radical sites, which thus ruled out substantial odd-spin derealization throughout the neighboring pyridine ring. However, only 8 and 9 (and 10) react extensively with oxygen by radical coupling, hence high spin densities on the radical site of the distonic ions do not necessarily lead to radical coupling reaction with oxygen. The very typical “spatially separated” ab initio charge and spin densities of 4–11 were used to classify them as distonic ions, whereas 1–3 show, as expected, “localized” electronic structures characteristic of conventional radical ions.  相似文献   

17.
The cyclopentadienyl(β-diketiminato)titanium and zirconium chlorides (η5-C5H5)MCl2(CH(C(NC6H4-4-OR)CH3)2) (M = Ti (4-dend), Zr (5-dend)), where R corresponds to the first generation carbosilane dendron (dendritic wedge) Si(CH2CH2SiMePh2)3, have been synthesised. After activation with methylaluminoxane, the activity of 4-dend and 5-dend as catalysts for ethylene polymerisation has been determined and compared with that of the non-dedritic counterpart (η5-C5H5)MCl2(CH(C(NC6H5)CH3)2) (M = Ti (4), Zr (5)).  相似文献   

18.
Treatment of the aldehyde (η4-C4Ph4)Co(η5-C5H4-CHO) (4b) with tert-butyllithium or phenyllithium yields the secondary alcohols (η4-C4Ph4)Co(η5-C5H4-CH(R)OH), where R=tert-butyl (5) or phenyl (6). Protonation of 5 and 6 at −80 °C furnishes the deep purple, cobalt-stabilized cations, 7 and 8, respectively, both of which exhibit restricted rotation about the external C5H4-CHR+ linkage on the NMR time-scale. These data indicate a minimum value for the barrier to rotation of 15 kcal mol−1, but it is certainly much higher, indicating a considerable degree of C-C double bond character. X-ray crystal structures of 4b, 5 and also of the ketone (η4-C4Ph4)Co(η5-C5H4-C(O)CH3 (4a) are reported. The secondary alcohol 5 exhibits disorder in the solid state because of the presence of diastereomers as a consequence of the stereogenic center at the α-carbon and the clockwise or anticlockwise propeller orientations of the tetraphenylcyclobutadiene ligand.  相似文献   

19.
A series of neutral bimetallic lanthanide aryloxides p-C6H4[OLnL(THF)n]2 [Ln = Y(1), Yb(2), Sm(3)(n = 1) and La(4)(n = 2), L = Me2NCH2CH2N{CH2-(2-O–C6H2–tBu2-3,5)}2] and alkoxides p-C6H4CH2[OLnL(THF)]2 [Ln = Y(5), Yb(6)] supported by an amine-bridged bis(phenolate) ligand have been synthesized through one-pot reactions of Ln(C5H5)3(THF), LH2 with p-benzenediol and 1,4-benzenedimethanol, respectively. All complexes have been fully characterized by elemental analyses, single-crystal X-ray diffraction analysis, and IR and multi-nuclear NMR spectroscopy(in the cases of 1, 4 and 5). Study of their catalytic behavior revealed that, in general, all complexes are efficient initiators for the polymerization of rac-lactide(LA) and rac-β-butyrolactone(BBL), except for 3 and 4 in the case of BBL. The influence imposed by lanthanides of different ionic radii and initiating groups of different structures on the activity, controllability, and stereoselectivity of polymerization were systematically studied and compared. Highly heterotactic PLA(Pr up to 0.99) and syndiotactic PHB(Pr ≈ 0.81) with high molecular weight and narrow polydispersity formed and were automatically capped with hydroxyl functionality at both ends.  相似文献   

20.
One-electron oxidation of 2-alkyl-1,4-dimethoxybenzenes 1a-f (2-alkyl=Me, Et, i-Pr, cy-C3H5CH2, PhCH2 and t-Bu) by 4-nitrobenzoyl peroxide 2 and pentaflurobenzoyl peroxide 3 was proved by the observation of great acceleration of decomposition of the peroxides at room temperature, the detection of the corresponding radical cations 1 +? a-f and product analysis. The product studies have disclosed that under the conditions employed (in acetonitrile at 40°C), the reaction pathways of the radical cations are greatly dependent on the nature of 2-alkyl substituents: Ring-4-nitrobenzoloxylation product at C 5 and C 6 were obtained exclusively in the reactions of the donors with aliphatic 2-alkyl substituents bearing at least one α-hydrogen atom, such as 1a, 1b, 1c and 1d; whereas in the case of 1e (with 2-benzyl group), both ring-substitution at C 5 (4e) and C 6 (5e) and deprotonation/4-nitrobenzoloxylation products 8e were isolated; from the donor without α-hydrogen atom, 1f, de-t-butylation products 12 and t-butyl 4-nitrobenzoate 13 were incorporated with ring-substitution at C 5 (4f) and C 6 (5f). Furthermore, the product distribution (4 over 5) is also affected by the bulkiness of 2-alkyl group. For all the electron-transfer reactions, large amounts of the benzoic acid (4-NO2-C6H4COOH or C6F5COOH) were generated and trace amounts of de-methylation product (2-alkyl-1,4-benzoqinones 6) were also detected by 1H NMR.  相似文献   

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