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.     

Chemistry of Diruthenium and Dirhodium Analogues of Pentaborane(9): Synthesis and Characterization of Metal N,S‐Heterocyclic Carbene and B‐Agostic Complexes

Building upon our earlier results on the synthesis of electron‐precise transition‐metal–boron complexes, we continue to investigate the reactivity of pentaborane(9) and tetraborane(10) analogues of ruthenium and rhodium towards thiazolyl and oxazolyl ligands. Thus, mild thermolysis of nido‐[(Cp*RuH)₂B₃H₇] ( 1 ) with 2‐mercaptobenzothiazole (2‐mbtz) and 2‐mercaptobenzoxazole (2‐mboz) led to the isolation of Cp*‐based (Cp*=η⁵‐C₅Me₅) borate complexes 5 a , b [Cp*RuBH₃L] ( 5 a : L=C₇H₄NS₂; 5 b : L=C₇H₄NOS)) and agostic complexes 7 a , b [Cp*RuBH₂(L)₂], ( 7 a : L=C₇H₄NS₂; 7 b : L=C₇H₄NOS). In a similar fashion, a rhodium analogue of pentaborane(9), nido‐[(Cp*Rh)₂B₃H₇] ( 2 ) yielded rhodaboratrane [Cp*RhBH(L)₂], 10 (L=C₇H₄NS₂). Interestingly, when the reaction was performed with an excess of 2‐mbtz, it led to the formation of the first structurally characterized N,S‐heterocyclic rhodium‐carbene complex [(Cp*Rh)(L₂)(1‐benzothiazol‐2‐ylidene)] ( 11 ) (L=C₇H₄NS₂). Furthermore, to evaluate the scope of this new route, we extended this chemistry towards the diruthenium analogue of tetraborane(10), arachno‐[(Cp*RuCO)₂B₂H₆] ( 3 ), in which the metal center possesses different ancillary ligands.     

Asymmetric,Three‐Component,One‐Pot Synthesis of Spiropyrazolones and 2,5‐Chromenediones from Aldol Condensation/NHC‐Catalyzed Annulation Reactions

A novel one‐pot, three‐component diastereo‐ and enantioselective synthesis of spiropyrazolones has been developed involving the aldol condensation of an enal to generate α,β‐unsaturated pyrazolones, which react with a second equivalent of enal through an N‐heterocyclic carbene (NHC)‐catalyzed [3+2] annulation. The desired spirocyclopentane pyrazolones are obtained in moderate to good yields and good to excellent stereoselectivities. Alternatively, starting from cyclic 1,3‐diketones, 2,5‐chromenediones are available through [2+4] annulation.     

NHC‐Pd complex‐catalyzed double carbonylation of aryl iodides with secondary amines to α‐keto amides

A series of palladium–NHC compounds were prepared and their catalytic activity in the double carbonylation of aryl iodides to synthesize α‐keto amides were examined. Palladium complexes bearing mixed NHC–phosphine exhibited high efficiency for the double carbonylation reaction. The effects of different solvents, base, temperature, carbon monoxide (CO), pressure, various amine and aryl iodides were investigated. Both electron‐rich and electron‐deficient aryl iodides afforded the corresponding substituted α‐keto amides in moderate to good yields. A possible mechanism was also proposed. Copyright © 2013 John Wiley & Sons, Ltd.     

A Silyliumylidene Cation Stabilized by an Amidinate Ligand and 4‐Dimethylaminopyridine

The synthesis and reactivity of a silyliumylidene cation stabilized by an amidinate ligand and 4‐dimethylaminopyridine (DMAP) are described. The reaction of the amidinate silicon(I) dimer [ L Si:]₂ ( 1 ; L =PhC(NtBu)₂) with one equivalent of N‐trimethylsilyl‐4‐dimethylaminopyridinium triflate [4‐NMe₂C₅H₄NSiMe₃]OTf and two equivalents of DMAP in THF afforded [ L Si(DMAP)]OTf ( 2 ). The ambiphilic character of 2 is demonstrated from its reactivity. Treatment of 2 with 1 in THF afforded the disilylenylsilylium triflate [ L′ ₂( L )Si]OTf ( 3 ; L′ = L Si:) with the displacement of DMAP. The reaction of 2 with [K{HB(iBu)₃}] and elemental sulfur in THF afforded the silylsilylene [ L SiSi(H){(NtBu)₂C(H)Ph}] ( 4 ) and the base‐stabilized silanethionium triflate [ L Si(S)DMAP]OTf ( 5 ), respectively. Compounds 2 , 3 , and 5 have been characterized by X‐ray crystallography.     

Structural Diversity of Copper(I)–N‐Heterocyclic Carbene Complexes; Ligand Tuning Facilitates Isolation of the First Structurally Characterised Copper(I)–NHC Containing a Copper(I)–Alkene Interaction

The preparation of a series of imidazolium salts bearing N‐allyl substituents, and a range of substituents on the second nitrogen atom that have varying electronic and steric properties, is reported. The ligands have been coordinated to a copper(I) centre and the resulting copper(I)–NHC (NHC=N‐heterocyclic carbene) complexes have been thoroughly examined, both in solution and in the solid‐state. The solid‐state structures are highly diverse and exhibit a range of unusual geometries and cuprophilic interactions. The first structurally characterised copper(I)–NHC complex containing a copper(I)–alkene interaction is reported. An N‐pyridyl substituent, which forms a dative bond with the copper(I) centre, stabilises an interaction between the metal centre and the allyl substituent of a neighbouring ligand, to form a 1D coordination polymer. The stabilisation is attributed to the pyridyl substituent increasing the electron density at the copper(I) centre, and thus enhancing the metal(d)‐to‐alkene(π*) back‐bonding. In addition, components other than charge transfer appear to have a role in copper(I)–alkene stabilisation because further increases in the Lewis basicity of the ligand disfavours copper(I)–alkene binding.     

2‐Hydroxy‐1,2,3,6‐tetrahydro‐azulen‐6‐carboxylic Acid Ethyl Ester—A Novel Precursor for a New Class of Liquid Crystalline Materials

A novel approach for the syntheses of carbene adduct 4 is reported. A ring-enlargement strategy was employed for the synthesis of precursors 5 and 6 and established the mechanism of the formation of azulene derivative 6. Synthesis of target precursor 13, a novel precursor for the synthesis of new mesogenic materials, and its various halogenated derivatives (14–16) was carried out.     

咪唑-多联吡啶钌配合物的合成、晶体结构和性能研究

以多联吡啶类配体取代咪唑3-位,合成了2个配体,进而得到了2个钌配合物[Ru（tpy-PhCH₂-Im-Naph）₂]（PF₆）₄（C1）和[Ru（2,2’-bpy）₂（2,2’-bpy-（CH₂-Im-CH₃）₂）]（PF₆）₄（C2）（tpy=2,2’：6’,2″-三联吡啶,bpy=2,2’-联吡啶,Im=咪唑,Naph=5,7-二甲基-1,8-萘啶）,通过核磁、质谱、元素分析,紫外、荧光等对这些化合物进行了表征,经X-射线晶体衍射分析确定了配合物C1的晶体结构。结构解析表明：配合物C1是离子型化合物,沿c轴方向堆积成规律的孔洞状。电化学性质测试揭示了氧化还原是一个单电子可逆的过程,对应的可逆对为Ru（Ⅲ）/Ru（Ⅱ）,E_1/2分别为1.26和1.32V。C1和C2与CO₂的加合物的红外光谱测试表明,这些化合物在碱的作用下能形成碳卡宾,可与CO₂结合。     

基于1-(2-吡啶甲基)-1, 2, 4-三唑的金属有机化合物的合成及反应研究

本文合成了1-（2-吡啶甲基）-1,2,4-三唑（L）,并研究了其与有机锡和羰基钼（钨）的配位反应,合成了通过三唑4位氮原子以单齿形式配位的有机锡衍生物L₂SnR₂Cl₂（R=Me,n-Bu或Ph）和羰基金属配合物LM（CO）₅（M=Mo或W）,以及N,N螯合双齿配位的四羰基金属配合物LM（CO）₄。当用氯化苄处理L时,制得了相应的三唑盐,该盐用氧化银处理后与M（CO）₅THF或M（CO）₄（NHC₅H₁₀）₂（NHC₅H₁₀为哌啶）反应,得到了基于三唑的氮杂环卡宾衍生物L’M（CO）₅和L’M（CO）₄（L’=1-（2-吡啶甲基）-4-苄基-1,2,4-三唑-5-碳烯）。X-射线单晶衍射分析表明,在L’M（CO）₅中氮杂环卡宾配体L’表现为通过卡宾碳配位的单齿配体;而在L’M（CO）₄中,L’表现为通过卡宾碳和吡啶氮原子配位的螯合[C,N]双齿配体。     

Strategy for the Construction of Diverse Poly‐NHC‐Derived Assemblies and Their Photoinduced Transformations

A series of supramolecular assemblies of types [Ag₈( L )₄](PF₆)₈ and [Ag₄( L )₂](PF₆)₄, obtained from the tetraphenylethylene (TPE) bridged tetrakis(1,2,4‐triazolium) salts H₄‐L(PF₆)₄ and Ag^I ions, is described. The assembly type obtained dependends on the N‐wingtip substituents of H₄‐L(PF₆)₄. Changes in the lengths of the N4‐wingtip substituents enables controlled formation of assemblies with either [Ag₄( L )₂](PF₆)₄ or [Ag₈( L )₄](PF₆)₈ stoichiometry. The molecular structures of selected [Ag₈( L )₄](PF₆)₈ and [Ag₄( L )₂](PF₆)₄ assemblies were determined by X‐ray diffraction analyses. While H₄‐ L (PF₆)₄ does not exhibit fluorescence in solution, their tetra‐NHC (NHC=N‐heterocyclic carbene) assemblies do upon NHC–metal coordination. Upon irradiation, all assemblies undergo a light‐induced, supramolecule‐to‐supramolecule structural transformation by an oxidative photocyclization involving phenyl groups of the TPE core, resulting in a significant change of the luminescence properties.