Dinuclear gold (I)-di-N-heterocyclic carbene complexes: syntheses,structure, density functional theory calculation and photoluminescence study

The synthesis and characterizations for a series of dinuclear gold (I)-di-NHC complexes, 1–8 through the trans-metalation method of their respective silver (I)-di-NHC complexes, i–viii are reported (where NHC = N-heterocyclic carbene). The successful complexation of a series of unusual non-symmetrical and symmetrical di-NHC ligands, 3,3'-(ethane-1,2-diyl)-1-alkylbenzimidazolium-1'-butylbenzimidazolium (with alkyl = methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, benzyl) with the gold (I) ions are suggested by elemental analysis, Fourier transform-infrared, ¹H- and ¹³C-NMR data. The ¹³C-NMR spectra of 1–8 show a singlet sharp peak in the range of 190.00–192.00 ppm, indicating the presence of a carbene carbon that bonded to the gold (I) ion. From single crystal X-ray diffraction data, the structure of complex 6 with the formula of [di-NHC-Au (I)]₂·2PF₆ is obtained [where NHC = 3,3'-(ethane-1,2-diyl)-1-hexylbenzimidazolium-1'-butylbenzimidazolium]. The photophysical study in solid state of 6 displays an intense photoluminescence with a strong emission maxima, λ_em = 480 nm, upon excitation at 340 nm at room temperature. Interestingly, the emission maximum at 77 K shows a structural character with a strong peak at 410 nm, a medium at 433 nm and a weak at 387 nm, accompanied by a tail band to about 500 nm.     

Novel hexadentate imidazolium salts in the rhodium-catalyzed addition of arylboronic acids to aldehydes

Four novel hexadentate imidazolium salts were synthesized from hexakis(bromomethyl)benzene and 1-substituted imidazole. The arylation of aldehydes with arylboronic acids was effected conveniently and in high yields by a catalyst system generated in situ from these hexadentate imidazolium salts, [Rh(COD)Cl]₂ and a base.     

二茂铁咪唑盐的合成及其在Suzuki-Miyaura反应中的应用

合成了硫醚官能化、膦官能化及未官能化的二茂铁咪唑盐,并研究了以其作为N-杂环卡宾配体前体对Pd催化的Suzuki-Miyaura偶联反应的影响,发现在4-甲基溴苯与苯硼酸偶联反应中以膦官能化的配体对催化性能提高有利,而硫醚官能化不利于催化性能提高。     

四种N-杂环卡宾钯配合物的电喷雾质谱研究

利用电喷雾质谱技术研究了四种N-杂环钯卡宾配合物,优化出较适宜检测的电喷雾质谱条件极性较高的溶剂(如乙腈),较低的离子源温度,样品浓度以1.0×10-4mol/L左右为宜,使用较低锥孔电压(5~35V).在此实验条件下,在全扫描电喷雾正离子谱中都会出现[M-I CH3CN] 及[M-I] 的质谱峰.通过源内碰撞诱导电离(CID)技术进一步分析样品在溶液中的性质.实验说明ESI不仅可作为一种分析工具,也可作为获得更多信息的一种方法,来研究有机金属基团在溶液中的性质.     

N-Heterocyclic Olefins as Electron Donors in Combination with Triarylborane Acceptors: Synthesis,Optical and Electronic Properties of D–π–A Compounds

N-heterocyclic olefins (NHOs), relatives of N-heterocyclic carbenes (NHCs), exhibit high nucleophilicity and soft Lewis basic character. To investigate their π-electron donating ability, NHOs were attached to triarylborane π-acceptors (A) giving donor (D)–π–A compounds 1 – 3 . In addition, an enamine π-donor analogue ( 4 ) was synthesized for comparison. UV–visible absorption studies show a larger red shift for the NHO-containing boranes than for the enamine analogue, a relative of cyclic (alkyl)(amino) carbenes (CAACs). Solvent-dependent emission studies indicate that 1 – 4 have moderate intramolecular charge-transfer (ICT) behavior. Electrochemical investigations reveal that the NHO-containing boranes have extremely low reversible oxidation potentials (e.g., for 3 , =−0.40 V vs. ferrocene/ferrocenium, Fc/Fc⁺, in THF). Time-dependent (TD) DFT calculations show that the HOMOs of 1 – 3 are much more destabilized than that of the enamine-containing 4 , which confirms the stronger donating ability of NHOs.     

The first palladium-catalyzed Sonogashira coupling of unactivated secondary alkyl bromides

A palladium-carbene catalyzed Sonogashira coupling of unactivated alkyl bromides with alkyl substituted alkynes is reported. For the first time, unactivated secondary alkyl halides were successfully employed in Sonogashira reactions.     

Facile Phenylphosphinidene Transfer Reactions from Carbene–Phosphinidene Zinc Complexes

Phosphinidenes [R-P] are convenient P₁ building blocks for the synthesis of a plethora of organophosphorus compounds. Thus far, transition-metal-complexed phosphinidenes have been used for their singlet ground-state reactivity to promote selective addition and insertion reactions. One disadvantage of this approach is that after transfer of the P₁ moiety to the substrate, a challenging demetallation step is required to provide the free phosphine. We report a simple method that enables the Lewis acid promoted transfer of phenylphosphinidene, [PhP], from NHC=PPh adducts (NHC=N-heterocyclic carbene) to various substrates to produce directly uncoordinated phosphorus heterocycles that are difficult to obtain otherwise.     

Self-Assembly of Benzimidazole-Derived Tris-NHC Ligands and AgI-Ions to Hexanuclear Organometallic Cages and Their Unusual Transmetalation Chemistry

Multi-ligand self-assembly to attain the Ag^I-N-heterocyclic carbene (NHC)-built hexanuclear organometallic cages of composition [Ag₆( 3 a , b )₄](PF₆)₆ from the reaction of benzimidazole-derived tris(azolium) salts [H₃- 3 a , b ](PF₆)₃ with Ag₂O was achieved. The molecular structures of the cages were established by X-ray diffraction studies along with NMR and MS analyses. The existence of a single assembly in solution was supported by diffusion-ordered spectroscopy (DOSY) ¹H NMR spectra. Further, transmetalation reactions of these self-assembled complexes, [Ag₆( 3 a , b )₄](PF₆)₆, with Cu^I/Au^I-ions provided various coinage metal-NHC complexes having diverse molecular compositions, which included the first example of a hexanuclear Cu^I-dodecacarbene complex, [Cu₆( 3 b )₄](PF₆)₆.     

Heterometallic Coii-Lii carboxylate complexes with N-heterocyclic carbene,triphenylphosphine and pyridine: a comparative study of magnetic properties

Heterometallic Coii-Lii compounds with N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), tri phenylphosphine (Ph3P) and pyridine (py), [Co2Li2(Piv)6(IMes)2] (Piv is the anion of pivalic acid), [Co2Li2(Piv)6(Ph3P)2] and [Co2Li2(Fur)6(py)2] (Fur is the anion of 2-furoic acid), respectively, have been prepared and structurally characterized by X-ray crystallography. Easy-plane magnetic anisotropy in Coii complexes with pseudo-tetrahedral cores CoO3X (X = C, P and N) was revealed by measuring the magnetic properties together with quantum-chemical calculations using the SA-CASSCF/NEVPT2 approach. The field-induced slow magnetic relaxation of the complexes was mainly attributed to the Raman and direct processes.     

Intramolecular Nitrene Insertion into Saturated C−H-Bond-Mediated C−N Bond Cleavage of a Coordinated NHC Ligand

Ruthenium(II) complexes bearing a tridentate bis(N-heterocyclic carbene) ligand reacted with iminoiodanes (PhI=NR) resulting in the formation of isolable ruthenium(III)–amido intermediates, which underwent cleavage of a C−N bond of the tridentate ligand and formation of an N-substituted imine group. The Ru^III–amido intermediates have been characterized by ¹H NMR, UV/Vis, ESI-MS, and X-ray crystallography. DFT calculations were performed to provide insight into the reaction mechanism.