共查询到20条相似文献,搜索用时 15 毫秒
1.
Berthold Hoge Christoph Thösen Tobias Herrmann Patricia Panne Ingo Pantenburg 《Journal of fluorine chemistry》2004,125(6):831-851
Chiral, bidentate phosphane ligands, so-called PP ligands, are most frequently synthesized by reacting chiral ditosylates with diarylphosphanide ions.To use the P(CF3)2− ion in nucleophilic substitution reactions, it is necessary to reduce the negative hyperconjugation, which is associated with a C-F activation. For this reason we synthesized different bis(trifluoromethyl)phosphanido complexes of mercury, silver and tungsten and investigated their use in nucleophilic substitution reactions. The most reactive compound, resulting from this study so far, is the pentacarbonylbis(trifluoromethyl)phosphanidotungstenate, [W{P(CF3)2}(CO)5]−, which exhibits nearly the same bonding situation for the P(CF3)2 unit as in the free P(CF3)2− ion. For use in synthesis of bis(trifluoromethyl)phosphane derivatives, Lewis acids are desirable, which stabilize the P(CF3)2− ion by an intermediary formation of a donor acceptor adduct and can be split off after the synthesis of bis(trifluoromethyl)phosphane derivatives, as could be achieved using the extremely weak Lewis acids, CS2 and acetone. These results could be established in the synthesis of the first example of an chiral, bidentate bis(trifluoromethyl)phosphane derivative.To synthesize a chiral, bidentate bis(pentafluorophenyl)phosphane derivative, a different synthetic strategy is necessary that does not involve the P(C6F5)2− ion, which decomposes even at low temperature. The implementation of functional P(CN)2− ions leads to the synthesis of functional, chiral bidentate dicyanophosphane derivatives which finally can be transformed into the corresponding bis(pentafluorophenyl)phosphane derivatives. 相似文献
2.
Schinzel S Müller R Riedel S Werner H Kaupp M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(26):7228-7235
The unusual bridging and semi‐bridging binding mode of tertiary phosphanes, arsanes, and stibanes in dinuclear low‐valent Group 9 complexes have been studied by density functional methods and bonding analyses. The influence of various parameters (bridging and terminal ligands, metal atoms) on the structural preferences and bonding of dinuclear complexes of the general composition [A1 M1(μ‐CH2)2(μ‐EX3)M2 A2] (M1, M2=Co, Rh, Ir; A1, A2=F, Cl, Br, I, κ2‐acac; E=P, As, Sb, X=H, F, CH3) has been analyzed. A number of factors have been identified that favor bridging or semi‐bridging modes for the phosphane ligands and their homologues. A more symmetrical position of the bridging ligand EX3 is promoted by more polar E? X bonding, but by less electronegative (softer) terminal anionic ligands. Among the Group 9 metal elements Co, Rh, and Ir, the computations clearly show that the 4d element rhodium exhibits the largest preference for a {M1(μ‐EX3)M2} bridge, in agreement with experimental observation. Iridium complexes should be valid targets, whereas cobalt does not seem to support well a symmetric bridging mode. Analyses of the Electron Localization Function (ELF) indicate a competition between a delocalized three‐center bridge bond and direct metal–metal bonding. 相似文献
3.
《Angewandte Chemie (International ed. in English)》2017,56(10):2720-2724
N‐Heterocyclic carbene based pincer ligands bearing a central silyl donor, [CSiC]−, have been envisioned as a class of strongly σ‐donating ligands that can be used for synthesizing electron‐rich transition‐metal complexes for the activation of inert bonds. However, this type of pincer ligand and complexes thereof have remained elusive owing to their challenging synthesis. We herein describe the first synthesis of a CSiC pincer ligand scaffold through the coupling of a silyl–NHC chelate with a benzyl–NHC chelate induced by one‐electron oxidation in the coordination sphere of a cobalt complex. The monoanionic CSiC ligand stabilizes the CoI dinitrogen complex [(CSiC)Co(N2)] with an unusual coordination geometry and enables the challenging oxidative addition of E−H bonds (E=C, N, O) to CoI to form CoIII complexes. The structure and reactivity of the cobalt(I) complex are ascribed to the unique electronic properties of the CSiC pincer ligand, which provides a strong trans effect and pronounced σ‐donation. 相似文献
4.
Metal complexes with reactive [ESiR3]? (E = S, Se, Te) or [S(SiMe2)]2? ligands provide a means for the delivery of {MEn}m? units in the formation of heterometallic polynuclear complexes and clusters. These complexes can be reacted with M′ salts to promote M–E–M′ interactions via the elimination of a silane side product. This research report summarizes the recent developments in the synthesis of silylchalcogenolate complexes of the d‐block metals with emphasis directed to those for which reactivity studies for the formation of ternary clusters have been carried out. The effects of varying the groups on the silyl moiety on the stability and reactivity of these precursor molecules are also discussed. 相似文献
5.
Salts of 3d, 4d, and 5d metals in the presence of the ligands 1,1,1,-tris(diphenylphosphinomethyl)ethane (triphos) or tris (2-diphenylphosphinoethyl) amine (np3) react with white phosphorus P4 (or yellow As4) to produce several mononuclear sandwich and dinuclear triple-decker sandwich complexes, which contain the unprecedented cyclo-triphosphorus (or cyclo-triarsenic) unit acting as a trihapto-ligand. In these complexes the metal atoms are bonded to the there phosphorus atoms of the phosphane ligand and to the three atoms of the cyclo-P3 or cyclo-As3 unit. The complexes are diamagnetic or have μeff-values corresponding to one or two unpaired electrons. The cyclo-P3 ligand is coordinatively unsaturated as proved by the fact that the mononuclear sandwich compounds may form Lewis-base adducts with electron-acceptor fragments. Reaction of the complexes (np)3M (M = Ni, Pd) with white P4 leads to formation of diamagnetic compounds [(np3)M(η1-P4)], in which the metal atom is bonded to the three phosphorus atoms of the np3-ligand and in addition to one P atom of the intact P4 molecule, which behaves as a monohapto-ligand. This article contains a review of the syntheses and structures of these complexes as well as a unified, albeit qualitative, approach to their bonding and properties. 相似文献
6.
Maribel Arroyo Consuelo Mendoza Sylvain Berns Hugo Torrens Hugo Morales-Rojas 《Polyhedron》2009,28(13):2625-2634
The reactions of OsO4 with excess of HSC6F5 and P(C6H4X-4)3 in ethanol afford the five-coordinate compounds [Os(SC6F5)4(P(C6H4X-4)3)] where X = OCH3 1a and 1b, CH3 2a and 2b, F 3a and 3b, Cl 4a and 4b or CF3 5a and 5b. Single crystal X-ray diffraction studies of 1 to 5 exhibit a common pattern with an osmium center in a trigonal-bipyramidal coordination arrangement. The axial positions are occupied by mutually trans thiolate and phosphane ligands, while the remaining three equatorial positions are occupied by three thiolate ligands. The three pentafluorophenyl rings of the equatorial ligands are directed upwards, away from the axial phosphane ligand in the arrangement “3-up” (isomers a). On the other hand, 31P{1H} and 19F NMR studies at room temperature reveal the presence of two isomers in solution: The “3-up” isomer (a) with the three C6F5-rings of the equatorial ligands directed towards the axial thiolate ligand, and the “2-up, 1-down” isomer (b) with two C6F5-rings of the equatorial ligands directed towards the axial thiolate and the C6F5-ring of the third equatorial ligand directed towards the axial phosphane. Bidimensional 19F–19F NMR studies encompass the two sub-spectra for the isomers a (“3-up”) and b (“2-up, 1-down”). Variable temperature 19F NMR experiments showed that these isomers are fluxional. Thus, the 19F NMR sub-spectra for the “2-up, 1-down” isomers (b) at room temperature indicate that the two S-C6F5 ligands in the 2-up equatorial positions have restricted rotation about their C–S bonds, but this rotation becomes free as the temperature increases. Room temperature 19F NMR spectra of 3 and 5 also indicate restricted rotation around the Os–P bonds in the “2-up, 1-down” isomers (b). In addition, as the temperature increases, the 19F NMR spectra tend to be consistent with an increased rate of the isomeric exchange. Variable temperature 31P{1H} NMR studies also confirm that, as the temperature is increased, the a and b isomeric exchange becomes fast on the NMR time scale. 相似文献
7.
The coordination chemistry of the water soluble phosphane oxide ligand tris[2‐isopropylimidazol‐4(5)‐yl]phosphane oxide, 4‐TIPOiPr, has been explored. A variety of 3d‐metal halide complexes have been prepared and the crystal structures of the solvates [(4‐TIPOiPr)ZnCl2]·MeOH·1/2dioxane ( 1 ·MeOH·1/2dioxane), [(4‐TIPOiPr)CoCl2]·H2O·2dioxane ( 2 ·H2O·2dioxane) and [(4‐TIPOiPr)2Ni(MeOH)2]Cl2·2MeOH ( 3 ·2MeOH) have been determined. All three structures show unprecedented coordination modes of the 4‐TIPOiPr ligand. Both zinc and cobalt complexes are coordinated in a bidentate κ2N fashion, whereas the nickel atom is coordinated by two ligands in a κN,O mode using one imidazolyl substituent and the P=O oxygen atom. 相似文献
8.
Reactions of [{M(μ‐Cl)(coe)2}2] (M = Rh, Ir; coe = cis‐cyclooctene) with the secondary phosphane tBu2PH under various molar ratios were investigated. Probably, for kinetic reasons, the reaction behavior of the rhodium species differed from that of the iridium analogue in some instances. During these studies complexes [MCl(tBu2PH)3] [M = Rh ( 1 ), Ir ( 2 )] were isolated, and solution variable‐temperature 31P{1H} NMR studies revealed that these complexes show a conformational rigidity on the NMR time scale. Spectra recorded in the temperature range from 173 to 373 K indicated in each case only one rotamer containing three chemically nonequivalent phosphanes due to the restricted rotation of these ligands about the M–P bonds and the tert‐butyl substituents around the P–C(tBu) bonds, respectively. Compound 1 showed in solution already at room temperature in several solvents a dissociation of a phosphane ligand affording the known complex [{Rh(μ‐Cl)(tBu2PH)2}2] beside the free phosphane. In contrast to these findings, the iridium analogue 2 remained completely unchanged under similar conditions and exhibited, therefore, some kinetic inertness. For a better understanding of the NMR spectroscopic investigations, the molecular structure of 1 in the solid state was confirmed by X‐ray crystallography. 相似文献
9.
Mooibroek TJ Schoon L Bouwman E Drent E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(47):13318-13333
The reactivity of palladium complexes of bidentate diaryl phosphane ligands (P2) was studied in the reaction of nitrobenzene with CO in methanol. Careful analysis of the reaction mixtures revealed that, besides the frequently reported reduction products of nitrobenzene [methyl phenyl carbamate (MPC), N,N′‐diphenylurea (DPU), aniline, azobenzene (Azo) and azoxybenzene (Azoxy)], large quantities of oxidation products of methanol were co‐produced (dimethyl carbonate (DMC), dimethyl oxalate (DMO), methyl formate (MF), H2O, and CO). From these observations, it is concluded that several catalytic processes operate simultaneously, and are coupled via common catalytic intermediates. Starting from a P2Pd0 compound formed in situ, oxidation to a palladium imido compound P2PdII?NPh, can be achieved by de‐oxygenation of nitrobenzene 1) with two molecules of CO, 2) with two molecules of CO and the acidic protons of two methanol molecules, or 3) with all four hydrogen atoms of one methanol molecule. Reduction of P2PdII?NPh to P2Pd0 makes the overall process catalytic, while at the same time forming Azo(xy), MPC, DPU and aniline. It is proposed that the Pd–imido species is the central key intermediate that can link together all reduction products of nitrobenzene and all oxidation products of methanol in one unified mechanistic scheme. The relative occurrence of the various catalytic processes is shown to be dependent on the characteristics of the catalysts, as imposed by the ligand structure. 相似文献
10.
Hubert Wadepohl 《Angewandte Chemie (International ed. in English)》1992,31(3):247-262
Transition-metal complexes in which two or more metal atoms are bridged by one or more arene ligands led a shadowy existence in comparison to the extensive class of mononuclear arene complexes. Arene bridges can occur in a variety of coordination modes and with almost all of the transition–metal elements of the periodic table. Nowhere else are found so many forms of distorted and bent arene rings. The binuclear compounds can be divided into two classes: adducts which show relatively weak metal–arene bonding and complexes which show strong arene–metal interaction. Most of the adducts are in equilibrium with mononuclear complexes in solution or are only stable in the solid state (often as polymers). In both classes syn and anti coordination occurs; their geometries show a wide variation between the extreme cases of η1 : η1-bridge and η6 : η6-triple-decker structure. Metal surfaces with chemisorbed arenes can be seen as a form of multinuclear arene–metal complexes. On transition-metal surfaces, benzene can be bonded to one, two, or four surface atoms. Molecular clusters with face-capping arene ligands that are bonded to three metal atoms have until now mainly been limited to two classes. The arenes bound to {(CO)3M}3 (M = Ru, Os) or (CpCo)3 clusters as μ3-η2 : η2 : η2 ligands show only a weak trigonal distortion towards a Kekulé structure. Detailed investigations of the molecular structure and ligand dynamics of [(CpCo)3(μ3-arene)] complexes considerably help the understanding of the bonding of arenes to metal clusters and to metal surfaces. 相似文献
11.
Adrien T. Normand Dr. Mikhail S. Nechaev Dr. Kingsley J. Cavell Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(29):7063-7073
A detailed experimental and DFT study (PBE level) of the reaction of [Pd(η3‐C3H5)(tmiy)(PR3)]BF4 (tmiy=tetramethylimidazolin‐2‐ylidene, PR3=phosphane), precursors to monoligated Pd0 species, with aryl electrophiles yielding 2‐arylimidazolium salt is reported. Experiments establish that an autocatalytic ligand transfer mechanism is preferred over PdIV and σ‐bond metathesis pathways, and that transmetalation is the rate‐determining step. Calculations indicate that the key step involves the concerted exchange of NHC and iodo ligands between two different PdII complexes. This is corroborated by experimental results showing the slower reaction of complexes containing the bulkier dipdmiy (dipdmiy = diisopropyldimethylimidazolin‐2‐ylidene). 相似文献
12.
Indre Thiel Dr. Haijun Jiao Dr. Anke Spannenberg Dr. Marko Hapke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(7):2548-2554
CpCoI‐olefin‐phosphite and CpCoI‐bisphosphite complexes were systematically prepared and their reactivity in [2+2+2] cycloaddition reactions compared with highly active [CpCo(H2C?CHSiMe3)2] ( 1 ). Whereas 1 is an excellent precursor for the synthesis of [CpCo(olefin)(phosphite)] complexes ( 2 a – f ), [CpCo(phosphite)2] complexes ( 3 a – e ) were prepared photochemically from [CpCo(cod)]. The complexes were evaluated in the cyclotrimerization reaction of diynes with nitriles yielding pyridines. For [CpCo(olefin)(phosphite)], as well as some of the [CpCo(phosphite)2] complexes, reaction temperatures as low as 50 °C were sufficient to perform the cycloaddition reaction. A direct comparison showed that the order of reactivity for the complex ligands was olefin2>olefin/phosphite>phosphites2. The complexes with mixed ligands favorably combine reactivity and stability. Calculations on the ligand dissociation from [CpCo(olefin)(phosphite)] proved that the phosphite is dissociating before the olefin. [CpCo(H2C?CHSiMe3){P(OPh)3}] ( 2 a ) was investigated for the co‐cyclization of diynes and nitriles and found to be an efficient catalyst at rather mild temperatures. 相似文献
13.
《Journal of molecular catalysis. A, Chemical》2001,165(1-2):45-54
The reaction of CO2 with (η2-dioxygen)-transition metal complexes to give peroxocarbonates has been modelled using the Impulse Oscillation Model (IOM).1 In accordance with our experimental findings concerning the reactivity of P3ClRh(η2-O2) (P=phosphane ligand) complexes towards carbon dioxide, application of the model to this reaction shows that the insertion of carbon dioxide into the OO bond is the preferred pathway. In fact, the probability for CO2 insertion into the OO bond equals maximum to 0.98 while into the M–O bond equals to 0.02. The concordance of calculated and experimental stretching frequencies indicates the possibility of identifying, through the vibration modes, proper ligands and metal systems that behave as selective catalysts at molecular level. 相似文献
14.
The mononuclear amidinate complexes [(η6‐cymene)‐RuCl( 1a )] ( 2 ) and [(η6‐C6H6)RuCl( 1b )] ( 3 ), with the trimethylsilyl‐ethinylamidinate ligands [Me3SiC≡CC(N‐c‐C6H11)2]– ( 1a– ) and[Me3SiC≡CC(N‐i‐C3H7)2]– ( 1b– ) were synthesized in high yields by salt metathesis. In addition, the related phosphane complexes[(η5‐C5H5)Ru(PPh3)( 1b )] ( 4a ) [(η5‐C5Me5)Ru(PPh3)( 1b )] ( 4b ), and [(η6‐C6H6)Ru(PPh3)( 1b )](BF4) ( 5 ‐BF4) were prepared by ligand exchange reactions. Investigations on the removal of the trimethyl‐silyl group using [Bu4N]F resulted in the isolation of [(η6‐C6H6)Ru(PPh3){(N‐i‐C3H7)2CC≡CH}](BF4) ( 6 ‐BF4) bearing a terminal alkynyl hydrogen atom, while 2 and 3 revealed to yield intricate reaction mixtures. Compounds 1a / b to 6 ‐BF4 were characterized by multinuclear NMR (1H, 13C, 31P) and IR spectroscopy and elemental analyses, including X‐ray diffraction analysis of 1b , 2 , and 3 . 相似文献
15.
16.
Ru‐Qiang Zou Rui‐Qin Zhong Ling Jiang Yusuke Yamada Nobuhiro Kuriyama Qiang Xu 《化学:亚洲杂志》2006,1(4):536-543
The reaction of cadmium(II) perchlorate with urocanic acid under different conditions created three novel coordination compounds: [Cd2(L2)2‐(L3)2(H2O)8] ( 1 ), {[Cd(L)(L2)](H2O)1/2}n ( 2 ), and {[Cd(L3)2](H2O)3/2(EtOH)}n ( 3 ), in which L, L2, and L3 are three urocanate tautomers. Complex 1 consists of two separate mononuclear units with different urocanate tautomers, which self‐assemble into a 3D hydrogen‐bonding network constructed by alternating 2D layers, whereas complexes 2 and 3 self‐assemble into 3D alpha‐polonium and four‐fold interpenetrated diamondoid networks, respectively. The tautomerism of the urocanate ligands and the enormous structural diversity of their complexes are present in this system, which illustrates that the reaction temperature, pressure, and the metal ions themselves act cooperatively to tune the tautomerism of the ligands and the frameworks of their metal coordination compounds. The fluorescence‐emission and nitrogen‐adsorption properties of these complexes are also investigated. 相似文献
17.
Patricia J. Nance Niklas B. Thompson Paul H. Oyala Jonas C. Peters 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6286-6290
Species with 2‐center, 3‐electron (2c/3e?) σ bonds are of interest owing to their fascinating electronic structures and potential for interesting reactivity patterns. Report here is the synthesis and characterization of a pair of zerovalent (d9) trigonal pyramidal Rh and Ir complexes that feature 2c/3e? σ bonds to the Si atom of a tripodal tris(phosphine)silatrane ligand. X‐ray diffraction, continuous wave and pulse electron paramagnetic resonance, density‐functional theory calculations, and reactivity studies have been used to characterize these electronically distinctive compounds. The data available highlight a 2c/3e? bonding framework with a σ*‐SOMO of metal 4‐ or 5dz2 parentage that is partially stabilized by significant mixing with Si (3pz) and metal (5‐ or 6pz) orbitals. Metal‐ligand covalency thus buffers the expected destabilization of transition‐metal (TM)‐silyl σ*‐orbitals by d–p mixing, affording well‐characterized examples of TM–main group, and hence polar, 2c/3e? σ “half‐bonds”. 相似文献
18.
Addison N. Desnoyer Weiying He Shirin Behyan Weiling Chiu Jennifer A. Love Pierre Kennepohl 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(20):5259-5268
The electronic nature of Ni π-complexes is underexplored even though these complexes have been widely postulated as intermediates in organometallic chemistry. Herein, the geometric and electronic structure of a series of nickel π-complexes, Ni(dtbpe)(X) (dtbpe=1,2-bis(di-tert-butyl)phosphinoethane; X=alkene or carbonyl containing π-ligands), is probed using a combination of 31P NMR, Ni K-edge XAS, Ni Kβ XES, and DFT calculations. These complexes are best described as square planar d10 complexes with π-backbonding acting as the dominant contributor to M−L bonding to the π-ligand. The degree of backbonding correlates with 2JPP from NMR and the energy of the Ni 1s→4pz pre-edge in the Ni K-edge XAS data, and is determined by the energy of the π*ip ligand acceptor orbital. Thus, unactivated olefinic ligands tend to be poor π-acids whereas ketones, aldehydes, and esters allow for greater backbonding. However, backbonding is still significant even in cases in which metal contributions are minor. In such cases, backbonding is dominated by charge donation from the diphosphine, which allows for strong backdonation, although the metal centre retains a formal d10 electronic configuration. This ligand-induced backbonding can be formally described as a 3-centre-4-electron (3c-4e) interaction, in which the nickel centre mediates charge transfer from the phosphine σ-donors to the π*ip ligand acceptor orbital. The implications of this bonding motif are described with respect to both structure and reactivity. 相似文献
19.
Patricia J. Nance Niklas B. Thompson Paul H. Oyala Jonas C. Peters 《Angewandte Chemie (International ed. in English)》2019,58(19):6220-6224
Species with 2‐center, 3‐electron (2c/3e?) σ bonds are of interest owing to their fascinating electronic structures and potential for interesting reactivity patterns. Report here is the synthesis and characterization of a pair of zerovalent (d9) trigonal pyramidal Rh and Ir complexes that feature 2c/3e? σ bonds to the Si atom of a tripodal tris(phosphine)silatrane ligand. X‐ray diffraction, continuous wave and pulse electron paramagnetic resonance, density‐functional theory calculations, and reactivity studies have been used to characterize these electronically distinctive compounds. The data available highlight a 2c/3e? bonding framework with a σ*‐SOMO of metal 4‐ or 5dz2 parentage that is partially stabilized by significant mixing with Si (3pz) and metal (5‐ or 6pz) orbitals. Metal‐ligand covalency thus buffers the expected destabilization of transition‐metal (TM)‐silyl σ*‐orbitals by d–p mixing, affording well‐characterized examples of TM–main group, and hence polar, 2c/3e? σ “half‐bonds”. 相似文献
20.
Pablo Ríos Hugo Fouilloux Dr. Josefina Díez Dr. Pietro Vidossich Prof. Dr. Agustí Lledós Dr. Salvador Conejero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(48):11346-11355
Platinum complexes [Pt(NHC′)(NHC)][BArF] (in which NHC′ denotes a cyclometalated N-heterocyclic carbene ligand, NHC) react with primary silanes RSiH3 to afford the cyclometalated platinum(II) silyl complexes [Pt(NHC-SiHR′)(NHC)][BArF] through a process that involves the formation of C−Si and Pt−Si bonds with concomitant extrusion of H2. Low-temperature NMR studies indicate that the process proceeds through initial formation of the σ-SiH complexes [Pt(NHC′)(NHC)(HSiH2R)][BArF], which are stable at temperatures below −10 °C. At higher temperatures, activation of one Si−H bond followed by a C−Si coupling reaction generates an agostic SiH platinum hydride derivative [Pt(H)(NHC′-SiH2R)(NHC)][BArF], which undergoes a second Si−H bond activation to afford the final products. Computational modeling of the reaction mechanism indicates that the stereochemistry of the silyl/hydride ligands after the first Si−H bond cleavage dictates the nature of the products, favoring the formation of a C−Si bond over a C−H bond, in contrast to previous results obtained for tertiary silanes. Furthermore, the process involves a trans-to-cis isomerization of the NHC ligand before the second Si−H bond cleavage. 相似文献