Fluorescence and crystal structures of new mercury(II) macrocyclic N-heterocyclic carbene complexes with ether chains

Polyerther-linked mercury(II) carbene complexes are synthesized by the reaction of carbene precursores with mercury(II) acetate. The binuclear carbene complexes with the chloride ion linkage are easily prepared by the reaction of mononuclear mercury carbene complexes with tetrabutylammoium chloride. The crystal structures reveal that the fluorescence of mercury complexes are related to the coordination mode of the ligands.     

极具潜在应用价值的催化剂——N-杂环卡宾金属配合物

N杂环卡宾的反应性能较高,与周期表中几乎所有的金属都能发生反应形成稳定的配合物.主要阐述了N杂环卡宾的结构与类型,其金属配合物的合成方法及在化学反应中的催化作用和应用前景.     

New Fischer carbene complexes of rhodium(i): preparation and 2-cyclopentenone ring synthesis by annelation to alkynes

A new type of metal carbene complexes of group 9, specifically a cationic Fischer carbene of rhodium(I), has been synthesized from chromium carbene complexes via double transfer of carbene and CO ligands. These complexes reveal a different reactivity than other transition metal carbenes, including their chromium precursors, toward neutral and electron-poor alkynes, giving selectively polysubstituted cyclopentenones.     

Cycloaddition reactions of alkoxy alkynyl Fischer carbene complexes with o-quinodimethanes (oQDMs)

[reaction: see text] The reaction of o-quinodimethanes (oQDMs) with alkoxy alkynyl Fischer carbene complexes is highly dependent on the carbene complex. Thus, for arylalkynyl carbene complexes, the initial [4 + 2]-cycloadduct evolves opening a new entry to the benzo[b]fluorene skeleton, which is present in many natural products. However, for alkenylalkynyl carbene complexes, the reaction takes place through the double bond, instead of the triple bond, in an unprecedented fashion, leading to new functionalized alkynyl carbene complexes.     

Density functional computations of the cyclopropanation of ethene catalyzed by iron (II) carbene complexes Cp(CO)(L)FeCHR,L = CO,PMe3, R = Me,OMe, ph,CO2Me

Density functional theory has been used to study the Fe‐catalyzed cyclopropanation of Fe‐carbene complexes with ethene. All the intermediates and transition states were optimized completely at the B3LYP/6‐31+G(d,p) level. Calculation results confirm that the cyclopropanation of Fe‐carbene complexes with ethene involves the two reaction paths I and II . In the reaction path I , the double bond of ethene attacks directly on the carbene carbon of Fe‐carbene complexes to generate the cyclopropane. In the reaction path II , ethene substitution for PMe₃ or CO in the Fe‐carbene complexes leads to the complexes M2 ; and the attack of one carbon of ethene on the carbene carbon results in the complexes M3 with a Fe? C? C? C four‐membered ring, and then generates the cyclopropane via the elimination reaction. For Fe‐carbene complexes A , C , D , E , and H , the main reaction mode is the reaction path I ; for Fe‐carbene complexes B , F , and G , the main reaction mode is the reaction path II . © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Synthesis, spectroscopic characterization and electronic structure of some new Cu(I) carbene complexes

Reaction of oligomeric Cu(I) complexes [Cu(Μ-S-C(=NR)(O-Ar-CH₃)]_n with Lewis acids gave Cu(I) carbene complexes, which were characterized by¹H and¹³C NMR spectroscopy. Cu(I) carbene complexes could be directly generated from RNCS, Cu(I)-OAr and Lewis acids; this method can be used to prepare Cu(I) carbene complexes with different substitutents on the carbene carbon. The complexes were unreactive towards olefins and do not undergo cyclopropanation. Electronic structure calculations (DFT) show that the charge on the carbene carbon plays an important role in controlling the reactivity of the carbene complex.     

Iron in the service of chromium: the ortho-benzannulation of trans,trans-dienyl Fischer carbene complexes

Chromium Fischer carbene complexes with trans,trans-dienyl substituents on the carbene carbon will react with diiron nonacarbonyl to give 2-alkoxycyclohexa-2,4-dienone iron tricarbonyl complexes and/or 2-alkoxyphenols in excellent yields. In the presence of silica gel or base, the cyclohexadienone complex will suffer loss of the iron and aromatization to give 2-alkoxyphenols. The formation of 2-alkoxyphenols from dienyl chromium carbene complexes is a known process (ortho-benzannulation) that only occurs with certain cis,trans-dienyl complexes. Control experiments show that trans,trans-dienyl chromium carbene complexes do not undergo conversion to 2-alkoxyphenols in the absence of an iron source. The process most likely occurs either via coordination of the dienyl unit in the chromium carbene complex to an iron tricarbonyl group and then loss of the chromium or via direct trans-metalation of the carbene ligand to give an iron carbene complex and then internal coordination to the dienyl unit such that cis to trans isomerization of the alpha,beta-double bond occurs.     

The first metal complexes of bis(diisopropylamino)carbene: synthesis, structure and ligand properties

The synthesis of rhodium(I) and iridium(I) complexes of the bis(diisopropylamino)carbene is described for the first time. The formamidinium chloride and the free bis(diisopropylamino)carbene (L) were used as consecutive precursor compounds to form the metal complexes. Spectroscopic and, for LRh(cod)Cl, crystallographic data are presented for the complexes LRh(cod)Cl and LIr(cod)Cl (L=bis(diisopropylamino)carbene). The ligand properties of the acyclic bis(diisopropylamino)carbene are compared with imidazolin-2-ylidenes and imidazolidin-2-ylidenes as ligands in related rhodium(I) carbonyl complexes. Bis(diisopropylamino)carbene is the most basic known carbene ligand to date.     

金属氮杂环卡宾配合物的抗肿瘤活性研究进展

自1978年顺铂成功地被开发成癌症临床治疗药物以来,金属配合物作为小分子抗癌药物的开发成为人们的研究热点。其中,氮杂环卡宾能与多种过渡金属中心形成稳定的共价键,这种特殊的稳定性使得金属氮杂环卡宾配合物具有被开发成药物的潜能。近年来,金属氮杂环卡宾配合物被发现具有良好的抗癌活性,激发了广大无机药物化学研究者的研究热情。综合笔者课题组在金属氮杂环卡宾抗肿瘤配合物方面的前期研究,本文将对银、金、铑和铂氮杂环卡宾配合物的抗肿瘤活性及作用机制进行综述,以期为新型金属氮杂环卡宾抗肿瘤化合物的设计合成提供参考。     

Synthesis of nitrogen-containing compounds using chromium Fischer carbene complexes

Synthetic utility of the Fischer-type carbene complexes of chromium for the preparation of nitrogen-containing compounds is demonstrated. Alkoxy carbene complexes reacted with imines to give (optically active) 3-pyrrolines and beta-methoxy allylic amine derivatives in good yields. The amino carbene complexes reacted with alpha,beta-unsaturated aldehydes to give substituted pyrroles in good yields.     

Computational and experimental studies on the mechanism of the photochemical carbonylation of group 6 Fischer carbene complexes

The photocarbonylation reaction of Group 6 Fischer carbene complexes has been studied by DFT and experimental procedures. The process occurs by intersystem crossing (ISC) from the lowest excited singlet state (S1) to the lowest triplet state (T1), the latter structure being decisive for the outcome of the reaction. Methylenepentacarbonylchromium(0) complexes, alkoxypentacarbonylchromium(0)carbene complexes, and alkoxyphosphinetetracarbonylchromium(0) carbene complexes have coordinatively unsaturated chromacyclopropanone T1 structures with a biradical character. The evolution of the metallacyclopropanone species occurs by a jump (spin inversion) to the S(0) hypersurface by coordination of a molecule of the solvent, leading to ketene-derived products in the presence of ketenophiles or reverting to the starting carbene complex in their absence. The T1 excited states obtained from methylenephosphinetetracarbonylchromium(0) complexes and pentacarbonyltungsten(0)carbene complexes are unable to produce the carbonylation. The reaction with ketenophiles is favored in coordinating solvents, which has been tested experimentally in the reaction of alkoxypentacarbonylchromium(0) complexes and imines.     

Ruthenium(II)-NHC-catalyzed (NHC = perhydrobenzimidazol-2-ylidene) alkylation of amines using the hydrogen borrowing methodology under solvent-free conditions

Transition Metal Chemistry - New ruthenium(II) complexes with N-heterocyclic carbene ligand were synthesized by transmetalation reactions between silver(I) N-heterocyclic carbene complexes and...     

Electronic structure of alkoxychromium(0) carbene complexes: a joint TD-DFT/experimental study

The joint computational (TD-DFT) experimental study of the UV-vis spectroscopy of alkoxychromium(0) carbene complexes accurately assigns the vertical transitions responsible for the observed spectra of these compounds. Both the LF and the MLCT band have a remarkably pi-pi* character, which has been demonstrated by the strong dependence of the absorptions with the donor/acceptor nature of the substituent in p-substituted styrylchromium(0) carbene complexes. The effect of the substituent is also related with the equilibrium geometry of the complexes and the occupations of the p atomic orbital of the carbene carbon atom. Additionally, the ferrocenyl moiety behaves in chromium(0) (Fischer) carbene complexes as a pi-donor group.     

Pd-catalyzed inter- and intramolecular carbene transfer from group 6 metal-carbene complexes.

The use of group 6 metal-carbene complexes in inter- and intramolecular carbene transfer reactions has been studied. Thus, pentacarbonyl[(aryl)(methoxy)carbene]chromium(0) and tungsten complexes, 10, efficiently dimerize at room temperature in the presence of diverse Pd(0) and Pd(II)/Et(3)N catalysts. The effect of additives (PPh(3), AsPh(3), or SbPh(3)) on the nature and the isomeric ratio of the reaction products is negligible. The nature of the reaction products is more catalyst-dependent for metal carbenes 12 bearing alkyl groups attached to the carbene carbon. In these cases, either carbene ligand dimerization or beta-hydrogen elimination reactions are observed, depending on the catalyst. The carbene ligand dimerization reaction can be used to prepare conjugated polyenes, including those having metal moieties at both ends of the polyene system, as well as enediyne derivatives. The intramolecular carbene ligand dimerization of chromium bis-carbene complexes 28 and 30 allows the preparation of mono- and bicyclic derivatives, with ring sizes from six to nine members. For bis-carbene derivatives the beta-hydrogen elimination reaction is inhibited, provided that both metal centers are tethered by an o-xylylene group. Other alkyl complexes 32 form new mononuclear carbene complexes 37 or decompose to complex reaction mixtures. The results obtained in these reactions may be explained by transmetalation from Cr(0) to Pd(0) and the intermediacy of Pd-carbene complexes. Aminocarbene-chromium(0) complexes 15, need harsher reaction conditions to transfer the carbene ligand, and this transfer occurs only in the presence of deactivated olefins. The corresponding insertion/hydrolysis products 48 resulted in these cases. A catalytic cycle involving transmetalation from a chromacyclobutane to a palladacyclobutane is proposed to explain these results.     

The [2 + 1] and [4 + 3] cyclization reactions of fulvenes with Fischer carbene complexes: new access to annulated cyclopentanones

Pentafulvenes are regioselectively cyclopropanated with group 6 Fischer carbene complexes leading to the homofulvene ring with complete endo selectivity. The homofulvene adducts undergo in turn a further cyclopropanation with ethyl diazoacetate or cyclopentannulation with a Fischer alkenyl carbene complex to provide substituted cyclopentanones after ozonolysis of the exocyclic carbon=carbon double bond. Fischer alkynyl carbene complexes also produce the corresponding alkynyl homofulvenes, albeit the exo stereoisomer is in this case exclusively or preferentially formed. Under moderate CO pressure, tungsten alkynyl carbene complexes cycloadd to pentafulvenes in a [4 + 3] fashion, giving rise to bicyclo[3.2.1]octadien-2-ones.     

Regioselective synthesis of substituted o-alkoxyphenol derivatives through thermal benzannulation of Fischer (alkenylcyclobutenyl)carbene complexes

A convenient, regioselective, and general synthetic method for producing highly substituted o-phenol-containing polycycles from Fischer (alkenylcyclobutenyl)carbene complexes has been described. The starting complexes have been synthesized by means of the [2 + 2] cycloaddition reaction of (alkenylethynyl)carbene complexes and a range of enol ethers, and in most cases, they have proven to be stable at room temperature and therefore isolable. The key step of the synthesis consists of the thermal benzannulation reaction of these novel pentacarbonyl dienyl Fischer complexes, which is an unprecedented transformation for these kinds of complexes. The unexpected behavior of (alkenylcyclobutenyl)carbene complexes has been rationalized in terms of their geometries.     

N-杂环卡宾的反应及应用

自从1991年Arduengo第一次分离得到稳定的游离N-杂环卡宾以后,N-杂环卡宾金属络合物的研究在近几年来得到了迅速的发展。N-杂环卡宾的反应性能较高,它们与周期表中几乎所有的元素都能发生反应。N-杂环卡宾金属络合物对许多反应有催化作用,它们是一类有潜在应用价值的催化剂。本文对近年来相关的研究成果进行了综述。     

Cycloadditions and annulations of transition metal carbene complexes

The synthetic aspects of several reactions from the multifaceted chemistry of Fischer carbene complexes are examined. Their benzannulation reactions with acetylenes are utilized in the synthesis of anthracyclinones via two approaches which differ by beginning at opposite ends of the molecule with either an aryl or an alkenyl substituted chromium carbene complex. The latter has been employed in a formal synthesis of daunomycinone. The Diels-Alder reactions of ,β-acetylenic chromium carbene complexes provide for a facile entry into substituted cyclohexenyl chromium carbene complexes that are subsequently employed in benzannulation reactions. These tandem cycloaddition/annulation reactions are incorporated into model studies for the synthesis of anthracyclinones and wentilactone A. Their potential is also demonstrated for coupling to yet a third reaction of organochromium compounds ; aromatic nucleophilic substitutions on arene chromium tricarbonyl complexes. The annulations of β,β-disubstituted alkenyl complexes provides for a regio- and stereoselective synthesis of 2,4-cyclohexadienones under neutral conditions at near ambient temperatures.     

Silver(I)-carbene complexes/ionic liquids: novel N-heterocyclic carbene delivery agents for organocatalytic transformations

[reaction: see text] N-Heterocyclic carbene (NHC) complexes with silver were investigated as sources of unsaturated NHC carbene catalysts via thermal decomposition. The NHC complex (1-ethyl-3-methylimidazol-2-ylidene)silver(I) chloride is an ionic liquid, and was found to catalyze the ring-opening polymerization of lactide at elevated temperatures to give narrowly dispersed polylactide of predictable molecular weight. Silver-carbene complexes can also be used for the catalysis of small molecule transesterification reactions. Thermolysis of the silver complexes in the presence of CS(2) yielded the zwitterionic CS(2) adducts of the carbene, implicating the intermediacy of the free carbene in these reactions.     

Trimethoxybenzene complexes of pentafluorophenylchlorocarbene

Pentafluorophenylchlorocarbene, generated by laser flash photolysis (LFP) of pentafluorophenylchlorodiazirine, formed π-type complexes with 1,3,5-trimethoxybenzene in pentane. The carbene and carbene complexes were in equilibrium with K = 3.21 × 10(5) M(-1) at 294 K. From the temperature dependence of K, ΔH° = -10.2 kcal/mol, ΔS° = -9.5 eu, and ΔG° = -7.4 kcal/mol at 298 K. The carbene complexes were characterized by UV-vis spectroscopy and computational analysis.