铂、铑N-杂环卡宾配合物在硅氢加成反应中的应用*

铂和铑的卡宾金属配合物作为催化剂应用于各种不饱和化合物的硅氢加成反应,表现出非常优良的催化性能和稳定的物理、化学性质,受到了化学工作者的广泛关注。本文对铂、铑N-杂环卡宾金属化合物作为催化剂在催化酮、炔烃、烯烃以及其它不饱和化合物硅氢加成反应中的应用作了介绍,并分析了该类催化剂在有机硅化学领域的应用前景。     

N-杂环卡宾金属配合物在酮硅氢加成反应中的新进展

N-杂环卡宾是一类新型催化剂和配体, 在有机化学中得到了极大的重视. N-杂环卡宾金属配合物的研究在近几年来得到迅速的发展,总结了酮硅氢加成反应中N-杂环卡宾金属配合物催化剂的应用新进展.     

N-杂环卡宾Ru配合物的合成及其在Suzuki偶联反应中的催化应用

合成了两个新的氮杂环卡宾金属钌配合物1和2,通过核磁共振氢谱、核磁共振碳谱、红外光谱和元素分析对其结构进行了表征,同时,X射线单晶衍射确证了配合物2的结构为cis(I)顺式构型.化合物1和2均能在温和的反应条件下有效催化卤代芳烃和苯硼酸的Suzuki偶联反应,并表现出较高的催化活性.     

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.     

N-heterocyclic carbene platinum complexes functionalized with a polyether chain and silyl group: Synthesis and application as a catalyst for hydrosilylation

The synthesis and characterization of new N-heterocyclic carbene platinum(II) complexes functionalized with a polyether chain and silyl group are described. In addition, their application towards the catalytic hydrosilylation of unsaturated carbon–carbon bonds, including alkenes, alkynes, vinyl ether, and unsaturated esters, is reported. These new complexes exhibit both excellent catalytic activity and selectivity for hydrosilylation. The catalytic system can be recycled >27 times.     

Cobalt Complexes Supported by Phosphinoquinoline Ligands for the Catalyzed Hydrosilylation of Carbonyl Compounds

P,N phosphinoquinoline based ligands differing by the nature of the phosphorus substituent (ⁱPr, Ph) were employed to synthesize a series of cobalt(II) complexes ( [LCoBr₂] , [L₂CoBr](PF₆) and [L’₂CoBr](PF₆) ). The latter were obtained in high yield and characterized among others by X-ray analysis and elemental analysis. Complex [L₂CoBr](PF₆) showed a very good catalytic activity for the hydrosilylation of various ketones. The catalysis proceeds at a low catalytic loading (1 mol %) with only 1 equivalent of Ph₂SiH₂ in mild conditions and was efficient with aliphatic or aromatic ketones giving moderate to excellent yields of the corresponding silylated ether.     

Highly Regio‐ and Stereoselective Hydrosilylation of Alkynes Catalyzed by Tridentate Cobalt Complexes

Several cobalt complexes bearing tridentate (NNN) ligands were synthesized and served as precatalysts for alkyne hydrosilylation with Ph₂SiH₂. For terminal alkynes, the catalyst L2 b‐CoCl₂ was selected, and resulted in the corresponding α‐vinylsilanes with high (Markovnikov) regioselectivity and extensive functional‐group tolerance. For internal diaryl alkynes, the catalyst L2 c‐CoCl₂ exhibited the best activity, and afforded E‐selective vinylsilanes through syn‐addition in excellent yield under mild conditions.     

氮杂环卡宾羰基氯钌配合物的合成、晶体结构及催化性质

合成了2个N-杂环卡宾钌配合物[RuCl₂（L1）（CO）]（1）,L1=（2,6-二（甲基咪唑-2-鎓盐）吡啶）和[RuCl₂（L2）（CO）]（2）,L2=（2,6-二（正丁基-2-鎓盐）吡啶）,并通过元素分析、红外光谱、核磁共振氢谱和核磁共振碳谱对它们的结构进行了表征,X-射线单晶衍射测定了配合物2的分子结构,结果表明配合物2属单斜晶系,C2/c空间群,a=1.8148（4）nm,b=1.1292（3）nm,c=1.1196（2）nm,β=108.862（3）°,且中心Ru（Ⅱ）离子是六配位,同时研究了配合物1和2在Suzuki-Miyaura偶联反应中的催化性质。     

氮杂环卡宾羰基氯钌配合物的合成、晶体结构及催化性质(英文)

合成了2个N-杂环卡宾钌配合物[RuCl2(L1)(CO)](1),L1=(2,6-二(甲基咪唑-2-鎓盐)吡啶)和[RuCl2(L2)(CO)](2),L2=(2,6-二(正丁基-2-鎓盐)吡啶),并通过元素分析、红外光谱、核磁共振氢谱和核磁共振碳谱对它们的结构进行了表征,X-射线单晶衍射测定了配合物2的分子结构,结果表明配合物2属单斜晶系,C2/c空间群,a=1.814 8(4)nm,b=1.129 2(3)nm,c=1.119 6(2)nm,β=108.862(3)°,且中心Ru(Ⅱ)离子是六配位,同时研究了配合物1和2在Suzuki-Miyaura偶联反应中的催化性质。     

新型氮杂环卡宾银(I)配合物的合成及其晶体结构

以取代苄氯(1a~1c)为起始原料,与咪唑经氮烷基化反应制得苄基咪唑氯盐(2a~2c); 2a~2c与氧化银经原位去质子化反应合成了3种新型的氮杂环卡宾银配合物--(NHC)AgCl［NHC: 1,3-二(4-甲氧基苄基)咪唑-2-亚基(3a), 1,3-二(3-甲氧基苄基)咪唑-2-亚基(3b)］和［(NHC)AgCl]₂［NHC=1,3-二(4-氯苄基)咪唑-2-亚基(3c)］,其结构经¹H NMR, ¹³C NMR, IR,元素分析和X-射线单晶衍射表征。3a~3c单晶结构均属单斜晶系,3a为P2₁/n空间群,3b和3c为P2₁/c空间群,3a和3b为单核银配合物,3c为双核银配合物。     

Synthesis,Structure and Catalytic Activity of NHC–AgI Carboxylate Complexes

A general synthetic route was used to prepare 15 new N‐heterocyclic carbene (NHC)–Ag^I complexes bearing anionic carboxylate ligands [Ag(NHC)(O₂CR)], including a homologous series of complexes of sterically flexible ITent ligands, which permit a systematic spectroscopic and theoretical study of the structural and electronic features of these compounds. The complexes displayed a significant ligand‐accelerated effect in the intramolecular cyclisation of propargylic amides to oxazolidines. The substrate scope is highly complementary to that previously achieved by NHC–Au and pyridyl–Ag^I complexes.     

Isomerization Reactions in Anionic Mesoionic Carbene‐Borates and Control of Properties and Reactivities in the Resulting CoII Complexes through Agostic Interactions

We present herein anionic borate‐based bi‐mesoionic carbene compounds of the 1,2,3‐triazol‐4‐ylidene type that undergo C?N isomerization reactions. The isomerized compounds are excellent ligands for Co^II centers. Strong agostic interactions with the “C?H”‐groups of the cyclohexyl substituents result in an unusual low‐spin square planar Co^II complex, which is unreactive towards external substrates. Such agostic interactions are absent in the complex with phenyl substituents on the borate backbone. This complex displays a high‐spin tetrahedral Co^II center, which is reactive towards external substrates including dioxygen. To the best of our knowledge, this is also the first investigation of agostic interactions through single‐crystal EPR spectroscopy. We conclusively show here that the structure and properties of these Co^II complexes can be strongly influenced through interactions in the secondary coordination sphere. Additionally, we unravel a unique ligand rearrangement for these classes of anionic mesoionic carbene‐based ligands.     

Sterically Demanding AgI and CuI N-Heterocyclic Carbene Complexes: Synthesis,Structures, Steric Parameters,and Catalytic Activity

The synthesis and full characterization of new air-stable Ag^I and Cu^I complexes bearing structurally bulky expanded-ring N-heterocyclic carbene (erNHC) ligands is presented. The condensation of protonated NHC salts with Ag₂O afforded a collection of Ag^I complexes, and their first use as ligand transfer reagents led to novel isostructural Cu^I or Au^I complexes. In situ deprotonation of the NHC salts in the presence of a copper(I) source, provides a library of new Cu^I complexes. The solid-state structures feature large N-C_NHC-N angles (118–128°) and almost identical angles between the aryl groups on the nitrogen atoms and the plane of the N-C-N unit of the carbene (i.e. torsion angles close to 0°). Among the steric parameters, the percent buried volume (%V_bur) values span easily in the 50–57 % range, and that one of (9-Dipp)CuBr complex (%V_bur=57.5) overcomes to other known erNHC–metal complexes reported to date. Preliminary catalytic experiments in the copper-catalyzed coupling between N-tosylhydrazone and phenylacetylene, afforded 76–93 % product at the 0.5–2.5 mol % catalyst loading, proving the stability of Cu^I erNHC complexes at elevated temperatures (100 °C).     

Catalytic Dibenzocyclooctene Synthesis via Cobalt(III)–Carbene Radical and ortho‐Quinodimethane Intermediates

The metalloradical activation of ortho‐benzallylaryl N‐tosyl hydrazones with [Co(TPP)] (TPP=tetraphenylporphyrin) as the catalyst enabled the controlled exploitation of the single‐electron reactivity of the redox non‐innocent carbene intermediate. This method offers a novel route to prepare eight‐membered rings, using base metal catalysis to construct a series of unique dibenzocyclooctenes through selective C_carbene?C_aryl cyclization. The desired eight‐membered‐ring products were obtained in good to excellent yields. A large variety of aromatic substituents are tolerated. The proposed reaction mechanism involves intramolecular hydrogen atom transfer (HAT) to Co^III–carbene radical intermediates followed by dissociation of an ortho‐quinodimethane that undergoes 8π cyclization. The mechanism is supported by DFT calculations, and the presence of radical‐type intermediates was confirmed by trapping experiments.     

Nickel Tetracarbonyl as Starting Material for the Synthesis of NHC-stabilized Nickel(II) Allyl Complexes

A novel, useful in situ synthesis for NHC nickel allyl halide complexes [Ni(NHC)(η³-allyl)(X)] starting from [Ni(CO)₄], NHC and allyl halides is presented. The reaction of [Ni(CO)₄] with (i) one equivalent of the corresponding NHC and (ii) with an excess of the corresponding allyl chloride at room temperature leads with elimination of carbon monoxide to complexes of the type [Ni(NHC)(η³-allyl)(X)]. This approach was used to synthesize the complexes [Ni(tBu₂Im)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 2 ), [Ni(iPr₂Im^Me)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 3 ), [Ni(iPr₂Im)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 4 ), [Ni(iPr₂Im)(η³-H₂C -C (H)-C (Me)₂)(Br)] ( 5 ), [Ni(Me₂Im^Me)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 6 ), and [Ni(EtiPrIm^Me)(η³-H₂C -C (Me)-C H₂)(Cl)] ( 7 ). The complexes 1 to 7 were characterized using NMR and IR spectroscopy and elemental analysis, and the molecular structures are provided for 2 and 7 . The allyl nickel complexes 1 – 7 are stereochemically non-rigid in solution due to (i) NHC rotation about the nickel-carbon bond, (ii) allyl rotation about the Ni–η³-allyl axis and (iii) π–σ–π allyl isomerization processes. The allyl halide complexes can be methylated as was demonstrated by the methylation of a number of the complexes [Ni(NHC)(η³-allyl)(X)] with methylmagnesium chloride or methyllithium, which led to isolation of the complexes [Ni(Me₂Im)(η³-H₂C -C (Me)-C H₂)(Me)] ( 8 ), [Ni(tBu₂Im)(η³-H₂C -C (Me)-C H₂)(Me)] ( 9 ), [Ni(iPr₂Im^Me)(η³-H₂C -C (Me)-C H₂)(Me)] ( 10 ), [Ni(iPr₂Im)(η³-H₂C -C (Me)-C H₂)(Me)] ( 11 ), [Ni(iPr₂Im)(η³-H₂C -C (H)-C (Me)₂)(Me)] ( 12 ), and [Ni(EtiPrIm^Me)(η³-H₂C -C (Me)-C H₂)(Me)] ( 13 ). These complexes were fully characterized including X-ray molecular structures for 10 and 11 .     

氮杂环卡宾的合成及在氢转移反应中的应用

利用氯甲基吡啶与咪唑反应制备了一系列含吡啶取代咪唑L1～L5,考察了所得咪唑衍生物与钌化合物在碱性条件下原位形成的氮杂卡宾钌络合物对苯胺与醇氢转移反应的催化活性.研究了碱的种类、钌前体、温度等对反应的影响,结果表明RuCl3 H2O/1-(2-吡啶甲基)-3-甲基碘化咪唑(L3)/KOH催化体系在185℃时对苯胺与乙二醇反应的催化活性较高,选择性生成N-羟乙基苯胺,TON(单位活性转化的底物分数)可达2130.此外,还考察了RuCl3 H2O/L3/KOH催化体系对苯胺与丁醇、环己醇、异丙醇、苯甲醇反应的催化性能.在催化剂作用下,醇与苯胺可形成亚胺及仲胺,伯醇可以自氢转移反应形成酯,反应产物的结构及选择性取决于醇的结构及反应条件.     

N-Heterocyclic Carbene Iron Complexes as Anticancer Agents: In Vitro and In Vivo Biological Studies

Cisplatin and its derivatives are commonly used in chemotherapeutic treatments of cancer, even though they suffer from many toxic side effects. The problems that emerge from the use of these metal compounds led to the search for new complexes capable to overcome the toxic side effects. Here, we report the evaluation of the antiproliferative activity of Fe(II) cyclopentadienyl complexes bearing n-heterocyclic carbene ligands in tumour cells and their in vivo toxicological profile. The in vitro antiproliferative assays demonstrated that complex Fe1 displays the highest cytotoxic activity both in human colorectal carcinoma cells (HCT116) and ovarian carcinoma cells (A2780) with IC₅₀ values in the low micromolar range. The antiproliferative effect of Fe1 was even higher than cisplatin. Interestingly, Fe1 showed low in vivo toxicity, and in vivo analyses of Fe1 and Fe2 compounds using colorectal HCT116 zebrafish xenograft showed that both reduce the proliferation of human HCT116 colorectal cancer cells in vivo.     

Triptycene‐Based Chiral and meso‐N‐Heterocyclic Carbene Ligands and Metal Complexes

Based on 1‐amino‐4‐hydroxy‐triptycene, new saturated and unsaturated triptycene‐NHC (N‐heterocyclic carbene) ligands were synthesized from glyoxal‐derived diimines. The respective carbenes were converted into metal complexes [(NHC)MX] (M=Cu, Ag, Au; X=Cl, Br) and [(NHC)MCl(cod)] (M=Rh, Ir; cod=1,5‐cyclooctadiene) in good yields. The new azolium salts and metal complexes suffer from limited solubility in common organic solvents. Consequently, the introduction of solubilizing groups (such as 2‐ethylhexyl or 1‐hexyl by O‐alkylation) is essential to render the complexes soluble. The triptycene unit infers special steric properties onto the metal complexes that enable the steric shielding of selected areas close to the metal center. Next, chiral and meso‐triptycene based N‐heterocyclic carbene ligands were prepared. The key step in the synthesis of the chiral ligand is the Buchwald–Hartwig amination of 1‐bromo‐4‐butoxy‐triptycene with (1S,2S)‐1,2‐diphenyl‐1,2‐diaminoethane, followed by cyclization to the azolinium salt with HC(OEt)₃. The analogous reaction with meso‐1,2‐diphenyl‐1,2‐diaminoethane provides the respective meso‐azolinium salt. Both the chiral and meso‐azolinium salts were converted into metal complexes including [(NHC)AuCl], [(NHC)RhCl(cod)], [(NHC)IrCl(cod)], and [(NHC)PdCl(allyl)]. An in situ prepared chiral copper complex was tested in the enantioselective borylation of α,β‐unsaturated esters and found to give an excellent enantiomeric ratio (er close to 90:10).     

Phosphorus‐Stabilized Titanium Carbene Complexes: Synthesis,Reactivity and DFT Studies

The synthesis of two novel titanium carbene complexes from the bis(thiophosphinoyl)methanediide geminal dianion 1 (SCS^2?) is described. Dianion 1 reacts cleanly with 0.5 equivalents of [TiCl₄(thf)₂] to afford the bis‐carbene complex [(SCS)₂Ti] ( 2 ) in 86 % yield. The mono‐carbene complex [(SCS)TiCl₂(thf)] ( 3 ) can also be obtained by using an excess of [TiCl₄(thf)₂]. The structures of 2 and 3 are confirmed by X‐ray crystallography. A strong nucleophilic reactivity towards various electrophiles (ketones and aldehydes) is observed. The reaction of 3 with N,N′‐dicyclohexylcarbodiimide (DCC) and phenyl isocyanate leads to the formation of two novel diphosphinoketenimines 8 a and 8 b . The bis‐titanium guanidinate complex 9 is trapped as the by‐product of the reaction with DCC. The X‐ray crystal structures of 8 a and 9 are presented. The mechanism of the reaction between complex 3 and DCC is rationalized by DFT studies.