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1.
2.
The author's studies of nucleophilic addition, chiefly to cationic complexes of the hydrocarbon metal and hydrocarbon metal carbonyl types are reviewed and related to other work in the area. Effects studied include stereospecificity, regioselectivity, competition with substitution, and rearrangements.  相似文献   

3.
The reaction of cyclodiborazane [Me(2)N-BH(2)](2) with the chloro(dihydrogen) ruthenium complex RuHCl(η(2)-H(2))(P(i)Pr(3))(2) (1) led to the formation of the unsymmetricaly coordinated dimethylaminoborane complex RuHCl(H(2)BNMe(2))(P(i)Pr(3))(2) (2). The dimethylaminoborane coordination (H(2)BNMe(2)) to the ruthenium center in 2 was carefully studied by combining X-ray, multinuclear NMR, and density functional theory (DFT) techniques, and compared with the recently reported osmium analogue which was originally formulated as a σ-B-H borinium complex [OsH(2)Cl(HBNMe(2))(P(i)Pr(3))(2)] (4). All our data are in favor of a bis(σ-B-H) coordination mode at a very activated stage in the case of the ruthenium complex 2, whereas in the osmium complex 4, full oxidative addition is favored leading to a complex better formulated as an osmium(IV) boryl species with an α-agostic B-H interaction. The synthesis and characterization of the symmetrical dihydride complex RuH(2)(H(2)BNMe(2))(P(i)Pr(3))(2) (3) from addition of the lithium dimethylaminoborohydride to 1 is reported for comparison.  相似文献   

4.
This highlight focuses on various luminescent complexes with different transition metal centres of d(6), d(8) and d(10) electronic configurations. Through the systematic study on the variation of ligands, structural and bonding modes of different metal centres, the structure-property relationships of the various classes of luminescent transition metal complexes can be obtained. With the knowledge and fundamental understanding of their photophysical behaviours, their electronic absorption and luminescence properties can be fine-tuned. Introduction of supramolecular assembly with hierarchical complexity involving non-covalent interactions could lead to research dimensions of unlimited possibilities and opportunities. The approach of "function by design" could be employed to explore and exploit the potential applications of such luminescent transition metal complexes for future development of luminescent materials.  相似文献   

5.
Chlorodivinylborane (I) prepared in situ from boron trichloride and dimethydivinyltin, reactions under photochemical conditions with ironpentacarbonyl and cyclopentadienyldicarbonylcobalt to give (η5-chlorodivinylborane)tricarbonyliron (II) and (η5-chlorodivinylborane)cyclopentadienylcobalt (III), respectively, in high yield. Complexes II and III readily undergo base-assisted nucleophilic substitution at boron.  相似文献   

6.
In order to examine the influence of the transition metal on the metal-disilanyl-fragment and especially the M-Si and Si-Si-bond polarized Raman spectra of the complexes (C(5)R(5))(CO)(2)Fe-Si(2)H(5) {R=H ( 1a); R=Me ( 1b)} and (C(5)R(5))(CO)(2)(PMe(3))M-Si(2)H(5) {R=Me, M=Mo ( 2); R=H, M=W ( 3)} have been recorded. The spectral data have been evaluated and interpreted on the basis of a normal coordinate analysis of the M-SiH(2)-Si-fragment including Br-Si(2)H(5) ( 4) and comparison with examinations of the M-SiH(3)-fragment.  相似文献   

7.
Quantum chemical calculations using density functional theory (B3LYP) were carried out to elucidate the reaction pathways for ethylene addition to the chromium and molybdenum complexes CrO(CH3)2(CH2) (Cr1) and MoO(CH3)2(CH2) (Mo1). The results are compared with previously published results of the analogous tungsten system WO(CH3)2(CH2) (W1). The comparison of the group-6 elements shows that the molybdenum and tungsten compounds Mo1 and W1 have a similar reactivity while the chromium compound has a more complex reactivity pattern. The kinetically most favorable reaction pathway for ethylene addition to Mo1 is the [2+2]Mo,C addition across the MoCH2 double bond which has an activation barrier of only 8.4 kcal/mol. The reaction is slightly exothermic with ΔER = −0.6 kcal/mol. The [2+2]Mo,O addition across the MoO double bond and the [3+2]C,O addition have much higher barriers and are strongly endothermic. The thermodynamically mostly favored reaction is the [1+2]Mo addition of ethylene to the metal atom which takes place after prior rearrangement of the Mo(VI) compound Mo1 to the Mo(IV) isomer Mo1g. The reaction is −19.2 kcal/mol exothermic but it has a large barrier of 34.5 kcal/mol. The kinetically and thermodynamically most favorable reaction pathway for ethylene addition to the chromium homologue Cr1 is the multiple-step process with initial rearrangements Cr1 → Cr1c → Cr1g which are followed by a [1+2]Cr addition yielding an ethylene π complex Cr1g + C2H4 → Cr1g-1. The highest barrier comes from the first step Cr1 → Cr1c which has an activation energy of 14.2 kcal/mol. The overall reaction is exothermic by −26.3 kcal/mol.  相似文献   

8.
Vibronically resolved resonant two-photon ionization and dispersed fluorescence spectra of the organometallic radicals CrC(2)H, CrCH(3), and NiCH(3) are reported in the visible and near-infrared wavelength regions. For CrC(2)H, a complicated vibronic spectrum is found in the 11 100-13 300 cm(-1) region, with a prominent vibrational progression having omega(e) (')=426.52+/-0.84 cm(-1), omega(e) (')x(e) (')=0.74+/-0.13 cm(-1). Dispersed fluorescence reveals a v(")=1 level of the ground state with DeltaG(1/2) (")=470+/-20 cm(-1). These vibrational frequencies undoubtedly pertain to the Cr-C(2)H stretching mode. It is suggested that the spectrum corresponds to the A (6)Sigma(+)<--X (6)Sigma(+) band system, with the CrC(2)H molecule being linear in both the ground and the excited state. The related CrCH(3) molecule displays a vibronic spectrum in the 11 500-14 000 cm(-1) region. The upper state of this system displays six sub-bands that are too closely spaced to be vibrational structure, but too widely separated to be K structure. It is suggested that the observed spectrum is a (6)E<--X (6)A(1) band system, analogous to the well-known B (6)Pi<--X (6)Sigma(+) band systems of CrF and CrCl. The ground state Cr-CH(3) vibration is characterized by omega(e) (")=525+/-17 cm(-1) and omega(e) (")x(e) (")=7.9+/-6 cm(-1). The spectrum of NiCH(3) lies in the 16 100-17 400 cm(-1) range and has omega(e) (')=455.3+/-0.1 cm(-1) and omega(e) (')x(e) (')=6.60+/-0.03 cm(-1). Dispersed fluorescence studies provide ground state vibrational constants of omega(e) (")=565.8+/-1.6 cm(-1) and omega(e) (")x(e) (")=1.7+/-3.0 cm(-1). Again, these values correspond to the Ni-CH(3) stretching motion. (c) 2004 American Institute of Physics.  相似文献   

9.
It is indicated that the effects of neglecting 1. the inter-atomic electrostatic field effects (M i ) and 2. the correction required to compensate the off-diagonal elements for the constant potential –Z implicitly included by approximating the diagonal elements as VSIE's largely cancel. To the extent that this cancellation holds, previous EH calculations may be rationalised in this regard.  相似文献   

10.
Pyridinium 2-carboxylates decompose thermally in the presence of a variety of late transition metal precursors to yield the corresponding 2-pyridylidene-like complexes. The mild reaction conditions and structural diversity that can be generated in the heterocyclic ring make this method an attractive alternative for the synthesis of 2-pyridylidene complexes. IR spectra of the Ir(i) carbonyl compounds [IrCl(NHC)(CO)(2)] indicate that these N-heterocyclic carbene ligands are among the strongest σ-electron donors.  相似文献   

11.
Salen metal complexes incorporating two chiral BINOL moieties have been synthesized and characterized by X-ray crystallography. The X-ray structures show that this new class of Ni-BINOL-salen catalysts contains an unoccupied apical site for potential coordination of an electrophile and naphthoxides that are independent from the Lewis acid center. These characteristics allow independent alteration of the Lewis acidic and Br?nsted basic sites. These unique complexes have been shown to catalyze the Michael reaction of dibenzyl malonate and cyclohexenone with good selectivity (up to 90% ee) and moderate yield (up to 79% yield). These catalysts are also effective in the Michael reaction between other enones and malonates. Kinetic data show that the reaction is first order in the Ni*Cs-BINOL-salen catalyst. Further experiments probed the reactivity of the individual Lewis acid and Br?nsted base components of the catalyst and established that both moieties are essential for asymmetric catalysis. All told, the data support a bifunctional activation pathway in which the apical Ni site of the Ni*Cs-BINOL-salen activates the enone and the naphthoxide base activates the malonate.  相似文献   

12.
In the present review we address scarcely studied application area of NMR spectroscopy — investigation of molten state and solvent-free systems. In such a case NMR spectra are recorded without a solvent and without magnetic field stabilization on any nucleus. Taking our recent studies of catalytic addition of sulfur- and selenium-containing compounds to alkynes as examples, we describe most important practical aspects of NMR studies and their application for solving important chemical problems. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 740–746, April, 2008.  相似文献   

13.
It is now well-known that (2)H solid-state NMR techniques can bring a better understanding of the interaction of deuterium with metal atoms in organometallic mononuclear complexes, clusters or nanoparticles. In that context, we have recently obtained experimental quadrupolar coupling constants and asymmetry parameters characteristic of deuterium atoms involved in various bonding situations in ruthenium clusters, namely D(4)Ru(4)(CO)(12), D(2)Ru(6)(CO)(18) and other related compounds [Gutmann et al., J. Am. Chem. Soc., 2010, 132, 11759], which are model compounds for edge-bridging (μ-H) and face-capping (μ(3)-H) coordination types on ruthenium surfaces. The present work is in line with density functional theory (DFT) calculations of the electric field gradient (EFG) tensors in deuterated organometallic ruthenium complexes. The comparison of quadrupolar coupling constants shows an excellent agreement between calculated and observed values. This confirms that DFT is a method of choice for the analysis of deuterium NMR spectra. Such calculations are achieved on a large number of ruthenium clusters in order to obtain quadrupolar coupling constants characteristic of a given coordination type: terminal-D, η(2)-D(2), μ-D, μ(3)-D as well as μ(4)-D and μ(6)-D (i.e. interstitial deuterides). Given the dependence of such NMR parameters mainly on local symmetry, these results are expected to remain valid for large assemblies of ruthenium atoms, such as organometallic ruthenium nanoparticles.  相似文献   

14.
Summary Formylferrocenyl-3-hydroxyl-2-naphthoylhydrazone and its transition metal coordination compounds have been synthesized and characterized by elemental analyses, i.r., 1H-n.m.r., u.v.-vis., t.g.-d.t.a. and molar conductivities. The results show that the ligand coordinates to transition metal ions in the enolic form, accompanied by the release of acetate or nitrate.  相似文献   

15.
Summary Acetylferrocenyl-3-hydroxyl-2-naphthoylhydrazone and its transition metal coordination compounds were prepared. The composition and properties of the ligand and the nature of metal to ligand bonding in its coordination compounds were characterized by elemental analyses, i.r. spectra, n.m.r. spectra, u.v.-vis. spectra, thermal analyses and molar conductivities.  相似文献   

16.
Conclusion and extensions We hope that this Review has made readers more aware of solvation of inorganic complexes, and of the importance of such knowledge in understanding their chemistryperhaps particularly their reactivity. The approach just set out for inorganic complexes should be of considerable value in the field or organometallic chemistry. In particular, informed use of solvation characteristics should help in optimising conditions for organometallic reactions and in homogeneous catalysis. Unfortunately, solvation data on reactants are too sparse (the subject index ofComprehensive Organometallic Chemistry contains justthree entries under solubility!) for serious examination of reactivity trends in terms of initial state and transition state contributions to be possible in almost all areas. Moreover, there are some fundamental problems over transfer parameters. Thus, a favourite electrochemical assumption is that the ferrocene/ferrocinium redox potential is independent of solvent. Yet, the dependence of rate constants on medium for outer-sphere electron transfer in the ferrocene/ferrocinium system can only be understood(66) in terms of specific solvation effects which are incompatible with the parallel solvation changes of these two substrates implicit in the redox potential assumption. The solvation of organometallic species should prove a most rewarding area for continued study, but it will be some time before the overall picture becomes as clear as in the more limited area of classical transition metal complexes considered in the present Review.  相似文献   

17.
Cyclometallated derivatives of 2-phenylpyridine (HL) are readily obtained by transmetallation reactions of 2-(2′-pyridyl)phenylmercury(II) chloride, [Hg(L)Cl], with labile transition metal compounds. The products of these reactions are cyclometallated, containing metalcarbon bonds. The yields are high, and comparable with or better than those obtained from direct reactions with 2-phenylpyridine. The products are easily isolated, and are unequivocally metallated. The metal exchange reaction may be used to prepare cyclometallated complexes which are not available by direct reaction with 2-phenylpyridine. The use of the mercury(II) complex enables the use of kinetically inert chloro complexes in the transmetallation.  相似文献   

18.
The synthesis of the ruthenium σ-acetylides (η5-C5H5)L2Ru-CC-bipy (4a, L = PPh3; 4b, L2 = dppf; bipy = 2,2′-bipyridine-5-yl; dppf = 1,1′-bis(diphenylphosphino)ferrocene) is possible by the reaction of [(η5-C5H5)L2RuCl] (1) with 5-ethynyl-2,2′-bipyridine (2a) in the presence of NH4PF6 followed by deprotonation with DBU. Heterobimetallic Fc-CC-NCN-Pt-CC-R (10a, R = bipy; 10b, R = C5H4N-4; Fc = (η5-C5H5)(η5-C5H4)Fe; NCN = [1,4-C6H2(CH2NMe2)2-2,6]) is accessible by the metathesis of Fc-CC-NCN-PtCl (9) with lithium acetylides LiCC-R (2a, R = bipy; 2b, R = C5H4N-4).The complexation behavior of 4a and 4b was investigated.Treatment of these molecules with [MnBr(CO)5] (13) and {[Ti](μ-σ,π-CCSiMe3)2}MX (15a, MX = Cu(NCMe)PF6; 15b, MX = Cu(NCMe)BF4; 16, MX = AgOClO3; [Ti] = (η5-C5H4SiMe3)2Ti), respectively, gave the heteromultimetallic transition metal complexes (η5- C5H5)L2Ru-CC-bipy[Mn(CO)3Br] (14a: L = PPh3; 14b: L2 = dppf) and [(η5-C5H5)L2Ru-CC-bipy{[Ti](μ-σ,π-CCSiMe3)2}M]X (17a: L = PPh3, M = Cu, X = BF4; 17b: L2 = dppf, M = Cu, X = PF6; 18a: L = PPh3, M = Ag, X = ClO4; 18b: L2 = dppf, M = Ag, X = ClO4) in which the appropriate transition metals are bridged by carbon-rich connectivities.The solid-state structures of 4b, 10b, 12 and 17b are reported. The main structural feature of 10b is the square-planar-surrounded platinum(II) ion and its linear arrangement. In complex 12 the N-atom of the pendant pyridine unit coordinates to a [mer,trans-(NNN)RuCl2] (NNN = 2,6-bis-[(dimethylamino)methyl]pyridine) complex fragment, resulting in a distorted octahedral environment at the Ru(II) centre. In 4b a 1,1′-bis(diphenylphosphino)ferrocene building block is coordinated to a cyclopentadienylruthenium-σ-acetylide fragment. Heterotetrametallic 17b contains a (η5-C5H5)(dppf)Ru-CC-bipy unit, the bipyridine entity of which is chelate-bonded to [{[Ti](μ-σ,π-CCSiMe3)2}Cu]+. Within this arrangement copper(I) is tetra-coordinated and hence, possesses a pseudo-tetrahedral coordination sphere.The electrochemical behavior of 4, 10b, 12, 17 and 18 is discussed. As typical for these molecules, reversible oxidation processes are found for the iron(II) and ruthenium(II) ions. The attachment of copper(I) or silver(I) building blocks at the bipyridine moiety as given in complexes 17 and 18 complicates the oxidation of ruthenium and consequently the reduction of the group-11 metals is made more difficult, indicating an interaction over the organic bridging units.The above described complexes add to the so far only less investigated class of compounds of heteromultimetallic carbon-rich transition metal compounds.  相似文献   

19.
The low-temperature 1H NMR spectra of bis(ethylene)trimethylphosphinenickel (1), η5-cyclopentadienyl(ethylene)methylnickel (2a), bis(ethylene)-η5-cyclopentadienylcobalt (2b), [bis(1-ethyl-2,4,6-triphenylphosphorinyl)nickel]P,P′-nickel(ethylene) (3) and η5-cyclopentadienyl(ethylene)hydrido(triphenylphosphine)ruthenium (4) exhibit {AA′B′B} (1) {ABB′A} (2a and 2b), {ABA′B′} (3) or {ABCD} (4) spin patterns, respectively, for the complexed ethylene. A full line shape analysis including all the proton couplings was performed for the ethylene rotation in 1, 2a and 2b. In addition to olefin rotation, a reversible intramolecular β-H-elimination was confirmed for 4 by magnetization transfer experiments.  相似文献   

20.
Recently, we have demonstrated the capacity to separate chiral transition metal (TM) complexes of the type [M(diimine)(3)](n+) using CE buffers containing chiral tartrate salts. In separate work, several chromium(III)-tris-diimine complexes in particular have been shown to bind enantioselectively with calf-thymus (CT) DNA, and a qualitative assessment of the relative strength and enantiospecificity of this interaction is of significant interest in the characterization of these complexes as potential DNA photocleavage agents. Here, we describe two convenient approaches to investigate such binding behavior using chiral CE. For complexes with lower DNA affinities exhibiting primarily surface binding, DNA itself is used as the chiral resolving agent in the electrophoretic buffer. In this approach, resolution of the TM complexes into their Lambda and Delta isomers is achieved with the isomer eluting later exhibiting superior binding affinity toward DNA. For more strongly bound TM complexes containing ligands known to intercalate with DNA, the [Cr(diimine)(3)](3+) complexes are preincubated with oligonucleotide and subsequently enantiomerically resolved in a dibenzoyl-L-tartrate buffer system that facilitates analysis of the unbound TM species only. Differences in isomer binding affinity are distinguished by the relative peak areas of the Lambda- and Delta-isomers, and relative binding strengths of different complexes can be inferred from comparison of the total amount of unbound complex at equivalent DNA/TM ratios.  相似文献   

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