Effect of the nature of carbene fragments in the tungsten complexes PhMe2E-CH=W(NAr)(OR′)2 and Me3E-CH=W(NAr)(OR′)2 (E = C, Si) on their catalytic properties in olefin metathesis reactions

Catalytic properties of the silicon-containing carbene complexes of tungsten Me₃Si-CH=W(NAr)(OR′)₂(1) and PhMe₂Si-CH=W(NAr)(OR′)₂ (2) and their hydrocarbon analogs Me₃C-CH=W(NAr)(OR′)₂ (3) and PhMe₂C-CH=W(NAr)(OR′)₂ (4) (Ar = 2,6-Prⁱ ₂C₆H₃, R′ = CMe₂CF₃) were studied in homometathesis of hex-1-ene, metathesis polycondensation of deca-1,9-diene, and ring opening metathesis polymerization of cyclooctene. The nature of the carbene fragment in the tungsten catalysts substantially affects their catalytic activity. Silicon-containing catalysts 1 and 2 were found to be 3−5 times less active than their hydrocarbon analogs 3 and 4. Metathesis polymerization of cyclooctene in the bulk with initiators 1–4 completed within a few minutes to form a block. Stereoregularity of the formed polyoctenamers depends to a considerable extent on the nature of the carbene fragments in the starting initiators. Initiators 1–2 lead to polyoctenamers mainly containing the cis-units, whereas the use of complexes 3 and 4 affords polyoctenamers mainly containing the trans-units. The structures of novel compound 2 and known complexes 1, 3, and 4 were determined by X-ray diffraction analysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1840–1845, September, 2008.     

Synthesis and metathesis activity of ruthenium dimethylvinyl carbene complexes

Two new dimethylvinyl carbene complexes, RuCl₂(SIMes)(PPh₃)CHCHC(CH₃)₂ and RuCl₂(SIMes)(3BP)₂CHCHC(CH₃)₂, were synthesized from RuCl₂(PCp₃)₂CHCHC(CH₃)₂. Complex RuCl₂(SIMes)(3BP)₂CHCHC(CH₃)₂ does not suffer from the problem of incomplete initiation that has been observed for the other dimethylvinyl carbene complexes, as witnessed by complete and rapid reaction with ethyl vinyl ether. Acyclic diene metathesis (ADMET) polymerization of 1,9‐decadiene with these complexes was found to give polymers with chemical and thermal properties similar to those obtained with Schrock's molybdenum catalyst. These complexes are also catalysts for ring‐opening metathesis polymerization. The parent complex RuCl₂(SIMes)(PCp₃)CHCHC(CH₃)₂ was found to give polyoctenamer with high initial heats of fusion, suggesting a dependence of the “as formed” crystallinity of the polymer on the rate of the ROMP reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6134–6145, 2005     

Synthesis of trinuclear silicon-, germanium-, and tin-containing tungsten carbene complexes [(ButO)2(Cl)2W=CH]2EPh2 (E = Si, Ge, or Sn). Crystal structure of [(ButO)2(Cl)2W=CH]2SiPh2 complex

New trinuclear organosilicon, organogermanium, and organotin-containing tungsten carbene complexes Ph₂E[CH=WCl₂(OBu^t)₂]₂ (E = Si, Ge, or Sn) were synthesized by the reaction of the trinuclear carbyne complexes Ph₂E[C≡W(OBu^t)₃]₂ with HCl. The tin-containing carbene complex is thermally unstable and was identified in solution by ¹H and ¹³C NMR spectroscopy. The silicon-and germanium-tungsten carbene complexes were isolated in high yields as individual crystals and were characterized by elemental analysis, IR spectroscopy, and ¹H and ¹³C NMR spectroscopy. The structure of the silicon-containing complex Ph₂Si[CH=WCl₂(OBu^t)₂]₂ was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2424–2427, November, 2005.     

Tailored molybdenum imido alkylidene N-heterocyclic carbene complexes as latent catalysts for the polymerization of dicyclopentadiene

Three novel molybdenum imido alkylidene N-heterocyclic carbene (NHC) pre-catalysts, that is, Mo(N-t-Bu)(1-(2,6-diisopropylphenyl)-3-isopropyl-4-phenyl-1H-1,2,3-triazol-5-ylidene)(CHCMe₂Ph)(OTf)₂ ( I1 , OTf = CF₃SO₃), Mo(N-t-Bu)(1-(2,6-diisopropylphenyl)-3-isopropyl-4-phenyl-1H-1,2,3-triazol-5-ylidene)(CHCMe₂Ph)(OTf)(t-BuO) ( I2 ) and Mo(N-2,6-Me₂-C₆H₃)(1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)(CHCMe₂Ph)(OTf)₂ ( I3 ) are presented. Compared to complexes based on imidazol-2-ylidenes or imidazolin-2-ylidenes, (1-(2,6-diisopropylphenyl)-3-isopropyl-4-phenyl-1H-1,2,3-triazol-5-ylidene) used in precatalysts I1 and I2 exerts a comparably strong trans effect to the triflate groups trans to the NHC, while (1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene) used in I3 has a weaker trans effect on the triflate. In combination with a suitable second anionic ligand at molybdenum, that is, OTf, t-BuO, compounds I1 – I3 require higher temperatures to become active and can thus be used as truly room temperature latent pre-catalysts, even for a highly reactive monomer such as dicyclopentadiene (DCPD). When used as latent precatalysts, I1 – I3 offer access to poly-DCPD with different degrees of cross-linking and glass-transition temperatures (T_g). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3028–3033     

Syntheses and structures of layered compounds based on lanthanides(iii) and cubane molybdenum and tungsten telluride cyano complexes

Eight isostructural polymeric coordination compounds of the general formula [Ln(DMF)(H₂O)₄][Ln(DMF)₂(H₂O)₄][M₄Te₄(CN)₁₂]·DMF·nH₂O (Ln = Er, Ho, Gd, or Sm; M = W or Mo) were prepared for the first time by evaporation in air of aqueous solutions containing the cuboidal telluride anionic complex of tungsten [W₄Te₄(CN)₁₂]^6– or molybdenum [Mo₄Te₄(CN)₁₂]^7–, lanthanide chlorides, and dimethylformamide. The resulting polymeric coordination complexes with layered structures were characterized by X-ray diffraction analysis and IR spectra. The magnetic susceptibilities of the gadolinium complexes were measured.     

Synthesis,characterization and catalytic properties of cationic N-heterocyclic carbene silver complexes

Three new dibenzimidazolium salts bridged by 2-methylenepropane-1,3-diyl group were synthesized. Their dinuclear N-heterocyclic carbene Ag(I) complexes were prepared by the reactions of these salts with Ag₂O. The structures of the synthesized compounds were defined by nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, and LC-MSMS (for complexes) techniques. Stability of the silver complexes was confirmed by ¹H NMR spectroscopy. Catalytic activities of Ag(I) compounds were tested for three-component coupling reaction of some aldehydes, amines, and phenylacetylene.     

Mono-and polynuclear CoII complexes with 2-hydroxy-6-methylpyridine

The reaction of 2-hydroxy-6-methylpyridine with Co(NO₃)₂·6H₂O or Co(F₃CSO₃)₂·6H₂O in the absence of a deprotonating agent produces the mononuclear complexes Co(HL)₄(NO₃)₂ or Co(HL)₄(F₃CSO₃)₂ (HL is 6-methyl-2-pyridone), respectively. In the presence of triethylamine, the reaction affords the trinuclear complex Co₃(HL)₂(L)₄(NO₃)₂ or the heptanuclear dicationic complex [Co₇L₁₂]·(F₃CSO₃)₂·4MeCN in the case of cobalt nitrate or cobalt trifluoromethanesulfonate, respectively. When HL is deficient, the replacement of the trimethylacetate anions in polymeric cobalt pivalate [Co(OH)_n(OOCCMe₃)_2−n ]_x gives rise to the hexanuclear complex Co₆(μ₃-OH)₂(η²,μ₃-L)₂(μ-OOCCMe₃)₈(HOOCCMe₃)₄, whereas the HLCo₆(μ₃-OH)(η²,μ₃-L)₃(η²,μ-L) (μ₃-L)(μ₃-OOCCMe₃)(μ-OOCCMe₃)₄(η²-OOCCMe₃) complex is generated when HL is present in excess. The structures of the reaction products were established by X-ray diffraction. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1851–1862, November, 2006.     

Butylene linked palladium N-heterocyclic carbene complexes: Synthesis and catalytic properties

New bis(NHC)-Pd complexes were synthesized and characterized by elemental analysis, ¹H NMR, ¹³C NMR, and IR spectroscopy. The reaction of Pd(OAc)₂ and bis(benzimidazolium) salts in DMSO gave the monomeric palladium complex in which the N-heterocyclic carbene was bound to the metal centre. The crystal and molecular structure of the cis-dibromo{1,1′-di[2,3,4,5,6-pentamethylbenzyl]-3,3′-butylenedibenzimidazol-2,2′-diylidene}-palladium(II) complex was determined by single-crystal X-ray diffraction. The activity of the Pd(II) complexes in the direct arylation of benzothiazole with arylbromides was investigated. A preliminary catalytic study showed that these bis(NHC)-Pd complexes were highly active in the direct arylation of benzothiazole with arylbromides.     

Synthesis and catalytic properties of N -functionalised carbene complexes of rhodium(I)

Reaction of [RhCl(COD)]₂, with 1,3-dialkylimidazolinylidene (1) or 1,3-dialkylbenzimidazolinylidene (2) resulted in the formation of rhodium(I) 1,3-dialkylimidazolin-2-ylidene (3a-c) and 1,3-dialkylbenzimidazolin-2-ylidene (4a,b) complexes. Triethylsilane reacts with acetophenone derivatives in the presence of catalytic amounts of RhCl(COD)(1,3-dialkylimidazolin-2-ylidene) or RhCl(COD)(1,3-dialkylbenzimidazolin-2-ylidene) to give the corresponding silylethers in good yield (57–98%).     

Synthesis and structure of N-heterocyclic carbene complexes of rhodium and iridium derived from an imidazolium-linked cyclophane

This paper describes the synthesis, spectroscopic and structural characterisation, and electrochemical behaviour of some rhodium and iridium complexes of the form LM(X₁)(X₂)⁺, where L is a chelating bis(carbene) derived from an imidazolium-linked ortho-cyclophane. The complexes where X₁/X₂ = 1,5-cycooctadiene or norbornadiene were prepared from the imidazolium-linked cyclophane and the appropriate metal source. In these complexes, the M-L bonding was quite robust, but the diene could be displaced by CO to give the dicarbonyl complexes , from which one or both carbonyl ligands could be displaced by monodentate or bidentate phosphines, respectively. Structural studies revealed only minor variations in the cyclophane unit upon exchange of the ancillary ligands, in each case the rhodium complex being isomorphous with its iridium analogue. In cyclovoltammetric studies of LRh(dppe)⁺, reversible Rh(I/II) and Rh(II/III) redox couples were observed. The other rhodium complexes displayed more complex electrochemical behaviours and did not undergo simple reversible redox reactions.     

Synthesis and structures of silicon-, germanium-, and tin-containing imido-alkyl molybdenum complexes (ArN)2Mo(CH2EMe3)2 (E = Si, Ge, Sn)

New silicon-, germanium-, and tin-containing imido-alkyl molybdenum complexes (ArN)₂Mo(CH₂EMe₃)₂ (Ar is 2,6-diisopropylphenyl; E = Si (1), Ge (2), Sn (3)) were prepared in the crystalline state in 58–66% yields by the reactions of the (ArN)₂MoCl₂(DME) complex with alkyllithium derivatives Me₃ECH₂Li (E = Si or Ge) or the Grignard reagents Me₃ECH₂MgCl (E = Ge or Sn). The structures of complexes 1–3 and the known analog (ArN)₂Mo(CH₂Bu^t)₂ (4) were established by X-ray diffraction analysis. Complexes 1–3 were found to be isostructural. The coordination environment about the Mo atom can be described as a distorted tetrahedron. Complex 4 has a similar structure. The Mo-C distance tends to decrease with increasing electron donating ability of the EMe₃ group.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 597–600, March, 2005.     

Synthesis and crystal and molecular structures of cation-anionic complexes of five-coordinate silicon-containing disiloxane dications with lactamomethyl andN-methylacetamidomethyl C,O-chelating ligands

The reactions of bis(chloromethyl)dichlorosilane withN-trimethylsilyl lactams andN-trimethylsilyl-N-methylacetamide taken in a ratio of 1∶2 followed either by treatment with HgCl₂ in the presence of atmospheric moisture or by hydrolysis under a wet atmosphere afforded cation-anionic complexes, which contain disiloxane dications of the general formula [L₂SiOSiL₂]²⁺ (L is the lactamomethyl orN-methylacetamidomethyl bidentate ligand) and hexachlorodimercurate, tetrachloromercurate, and hydroxonium trichloride counter-ions, respectively. X-ray diffraction analysis demonstrated that the disiloxane dications in these complexes contain two five-coordinate Si atoms and occur as silicenium ions stabilized through two O→Si coordination bonds. In the case of lactamomethyl ligands, the disiloxane dications exist as diastereomers whose bischelate ligands adopt opposite configurations, whereas whenN-methylacetamidomethyl ligands are present, the bischelate ligands adopt identical configurations. The first example of the presence of a hydroxonium trichloride ion as a counter-ion in the crystal has been found. It consists of the hydroxonium cation, which holds three Cl⁻ anions through strong hydrogen bonds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 997–1007, May, 1998     

Synthesis of heterocyclic carbene ligands via 1,2,3-diheterocyclization of allenylidene complexes with dinucleophiles

Heterocyclic carbene complexes are accessible from π-donor-substituted allenylidene complexes, [(CO)₅CrCCC(NMe₂)Ph] (1) and [(CO)₅CrCCC(O-endo-Bornyl)OEt] (4), and various dinucleophiles by 1,2,3-diheterocyclization. The reaction of 1 with 1,2-dimethylhydrazine gives the 1,2-dimethylpyrazolylidene complex (2) in high yield in addition to small amounts of the α,β-unsaturated carbene complex [(CO)₅CrC(NMe₂)-C(H)C(NMe₂)Ph] (3). The analogous reaction of 4 with 1,2-dimethylhydrazine affords the 1,2-dimethylpyrazolylidene complex (5) and, via displacement of the C_γ-bound ethoxy substituent, the hydrazinoallenylidene complex [(CO)₅CrCCC(O-endo-Bornyl){NMe-N(H)Me}] (6). Treatment of 6 with catalytic amounts of acids induces cyclization to 5. On addition of 1,1-dimethylhydrazine to 1 the zwitterionic pyrazolium-5-ylidene complex (7) is formed. The reaction of 1 with 1,2-diaminocyclohexane affords a octahydro-benzo[1,4]diazepinylidene complex (10) and, via intermolecular substitution, a binuclear bisallenylidene complex (11). Thiazepinylidene complexes (12-14), containing 7-membered N/S-heterocyclic carbene ligands, are formed highly selectively in the reaction of 1 with 2-aminoethanethiol or related cysteine derivatives by a substitution/cyclization sequence. The analogous reaction of 1 with homocysteine methylester yields a thiazocanylidene complex (15). All new heterocyclic carbene ligands are strong donors exhibiting σ-donor/π-acceptor ratios similar to those of the known imidazolylidene complexes. On photolysis of 2 and 12 in the presence of triphenylphosphine, the corresponding cis-carbene tetracarbonyl triphenylphosphine complexes (16 and 17) are formed. The solid state structure of complexes 2, 7, 14, 15, and 16 is established by X-ray structural analysis.     

Bicyclic N-heterocyclic carbene (NHC) ligand precursors and their palladium complexes

Eight bicyclic amidinium precursors (3), prepared from R,S-tmcp (R,S-tmcp: (1R,3S)-diamino-1,2,2-trimethylcyclopentane) were described. Only five of the precursors (3a–e) could be converted to palladium complexes, (PdX₂(6,7-NHC)PEPPSI) (4) by treatment with PdCl₂, K₂CO₃, and pyridine (additional KBr was used for (PdBr₂(6,7-NHC)PEPPSI)). The salts and complexes were fully characterized by spectroscopic methods and X-ray crystallography.     

Dinuclear gold(I)-N-heterocyclic carbene complexes: Synthesis,characterization, and catalytic application for hydrohydrazidation of terminal alkynes

Dinuclear gold(I)-N-heterocyclic carbene complexes were developed for the hydrohydrazidation of terminal alkynes. The gold(I)-N-heterocyclic carbene complexes 2a-2b were synthesized in good yields from silver complexes synthesized in situ, which in turn were obtained from the corresponding imidazolium salts with Ag₂O in dichloromethane as a solvent. The new air-stable gold(I)-NHC complexes, 2a - 2b, were characterized using NMR spectroscopy, elemental analysis, infrared, and mass spectroscopy studies. The gold(I) complex 2a was characterized using X-ray crystallography. Bis-N-heterocyclic carbene–based gold(I) complexes 2a - 2b exhibited excellent catalytic activities for hydrohydrazidation of terminal alkynes yielding acylhydrazone derivatives. The working catalytic system can be used in gram-scale synthesis. In addition, the catalytic reaction mechanism of the hydrohydrazidation of terminal alkynes by gold(I)-NHC complex was studied in detail using density functional theory.     

钨卡宾络合物在有机合成中的应用

对钨卡宾络合物参与的反应机理和一些合成方法作了简要的介绍,并评述了部分钨卡宾络合物合成有机化合物的反应。     

Synthesis and structures of germanium-containing tungsten carbyne complexes Ph3gec≡w(ch2but)3 and Ph3GeC≡W(CH2SiMe3)3

New germanium-containing tungsten carbyne complexes Ph₃GeC≡W(CH₂R)₃ (R = Bu^t or SiMe₃) were synthesized by the reaction of the alkoxy derivative Ph₃GeC≡W(OBu^t)₃ with alkyllithium reagents RCH₂Li. The new compounds were isolated in individual form as crystals in 95 and 90% yields, respectively, and were characterized by elemental analysis, ¹H and ¹³C NMR spectroscopy, and X-ray diffraction. X-ray diffraction study showed that the coordination environment of the W and Ge atoms in the Ph₃GeC≡ W(CH₂Bu^t)₃ and Ph₃GeC≡W(CH₂SiMe₃)₃ complexes can be described as a distorted tetrahedron. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 213—216, February, 2006.