Haloacetylated enol ethers. 14 [6]. Reaction of β-alkoxyvinyl trifluoromethyl ketones with N-methylhydroxylamine

The reaction of a series of β-methoxyvinyl trifluoromethyl ketones [CF₃COC(R²)?C(OMe)R¹, where R¹ = Me, -(CH₂)₃-C3, -CH₂)₄-C3, Ph and R² = H, Me, -(CH₂)₃-C4, -(CH₂)₄-C4] with N-methylhydroxylamine is reported. The regiochemistry of the reaction are explained by MO calculation data.     

Isomere η2-Acyl- und σ-Alkyl(carbonyl)-Komplexe von Molybdän und Wolfram. Eine Studie zum Bildungs-mechanismus,zur Isomerisierungsgeschwindigkeit und zur Steuerung der Gleichgewichtslage

η²-Acyl and σ-Alkyl(carbonyl) Coordination in Molybdenum and Tungsten Complexes: Synthesis and Studies of the Isomerization Equilibria and Kinetics The anionic molybdenum and tungsten complexes [L_RM(CO)₃]^? (L_R^? = [(C₅H₅)Co{P(O)R₂}₃]^?, R = OCH₃, OC₂H₅, O-i-C₃H₇; M = Mo, W) have been alkylated with the iodides R′ I, R′ = CH₃, C₂H₅, i-C₃H₇, and CH₂C₆H₅. The reactivity pattern of the alkylation is in accord with a S_N2 mechanism. Depending on M, R′, reaction temperature, and time the η-alkyl (carbonyl) compounds [L_RM(CO)₃R′] and/or the isomeric η²-acyl compounds [L_RM(CO)₂(η²-COR′)] can be obtained. 8 new σ-alkyl(carbonyl) compounds and 15 new η²-acyl compounds have been isolated and characterized. The ¹H NMR and the IR spectra give conclusive evidence that the σ-alkyl(carbonyl) compounds [L_RM(CO)₃R′] are formed as the primary products of the alkylation and that they isomerize partly or completely to give the η²-acyl compounds [L_RM(CO)₂(η²-COR′)]. The position of the equilibrium σ-alkyl(carbonyl)/η²-acyl is controlled by the steric demands of the groups R′ and the ligands L_R^?. The molybdenum compounds isomerize much more readily than the tungsten compounds. The rate constants of the isomerization processes [L_RMo(CO)₃CH₃] → [L_RMo(CO)₂(η²-COCH₃)], R = OCH₃, OC₂H₅, and O-i-C₃H₇, measured at 305 K in acetone-d₆, are 6–8 x 10^?3 s^?1.     

Synthesis,Characterizations, and Structure of Group 4 Metallocene Complexes of Some Difunctional Ligands Containing Oxygen and Sulfur Donors

Reactions of CH₃OCH₂CH₂OH, PhOCH₂CH₂OH, o-CH₃OC₆H₄CH₂OH, or PhSCH₂CH₂OH with Cp₂ZrCl₂ in the presence of NEt₃ gave series monomeric complexes Cp₂ZrClX (X = OCH₂CH₂OCH₃ ( 1 ), OCH₂CH₂OPh ( 2 ), o-OCH₂C₆H₄OCH₃ ( 3 ) or OCH₂CH₂SPh ( 4 )). In a reaction of Cp₂TiCl₂ with PhSCH₂CH₂OH in the presence of NEt₃, the complex Cp₂TiCl(OCH₂CH₂SPh) ( 5 ) was obtained. These complexes were characterized by the ¹H and ¹³C NMR, and the chemical shifts of the Cp rings for complexes 1–4 are nearly identical, despite differences in ligands for an indication of similar structures of these complexes around the metal center. Complex 4 crystallizes into the monoclinic P2₁/c space group with a = 13.806(3) Å, b = 16.394(3) Å, c = 7.838(2) Å, β = 100.85(3)° Z = 4, R = 0.029, R_w = 0.044, and Gof = 1.19. The molecular structure of complex 4 shows that the 2-(phenylthio)ethoxide bonds to the Zr metal center through the alkoxide donor leaving the thioether donor free from coordination.     

Syntheses,Structures, and Biological Activity of NiII,PdII, and PtII Complexes with New Tetradentate Benzamidine Ligands

N‐(Dialkylthiocarbamoyl)benzimidoyl chlorides react with o‐(salicylidenimine)benzylamine with formation of a novel class of tetradentate benzamidine ligands (H₂L^Et and H₂L^Morph), which readily react with Ni(CH₃COO)₂, [PdCl₂(CH₃CN)₂], and [PtCl₂(PPh₃)₂] under formation of complexes of the composition [M(L^R)] [M = Ni ( 4 ), Pd ( 5 ), Pt ( 6 )]. In all complexes, H₂L^R is doubly deprotonated and bonded to the metal ion via its N₂OS donor set and establishes a distorted square‐planar coordination sphere. The antiproliferative effects of the compounds on MCF‐7 and Hep‐G2 cells were studied. The complexes of H₂L^Morph are generally more active than those of H₂L^Et. While H₂L^Et and its complexes exhibit stronger effects on the Hep‐G2 line, the corresponding compounds of H₂L^Morph show almost equal effects on the two cell lines. In each series of compounds, the cytotoxicity increases in the order H₂L^R << 4 < 5 < 6 .     

Synthesis,Structure and Characterization of Dinuclear Pentacoordinate Molybdenum(V) Complexes with Thiosemicarbazone Ligands

New dinuclear pentacoordinate molybdenum(V) complexes, [Mo₂^VO₃L₂] [L = thiosemicarbazonato ligand: C₆H₄(O)CH:NN:C(S)NHR′ and C₁₀H₆(O)CH:NN:C(S)NHR′; R′ = H, CH₃, C₆H₅) were obtained either by oxygen atom abstraction from Mo^VIO₂L with triphenylphosphine or by using [Mo₂O₃(acac)₄] in the reaction with the corresponding ligands H₂L. Crystal and molecular structure of [Mo₂O₃{C₆H₄(O)CH:NN:C(S)NHC₆H₅}₂] · CH₃CN has been determined by the single‐crystal X‐ray diffraction method.     

Functionalized Organotin‐Chalcogenide Complexes That Exhibit Defect Heterocubane Scaffolds: Formation,Synthesis, and Characterization

The synthesis of new functionalized organotin‐chalcogenide complexes was achieved by systematic optimization of the reaction conditions. The structures of compounds [(R^{1, 2}Sn)₃S₄Cl] ( 1 , 2 ), [((R²Sn)₂SnS₄)₂(μ‐S)₂] ( 3 ), [(R^{1, 2}Sn)₃Se₄][SnCl₃] ( 4, 5 ), and [Li(thf)_n][(R³Sn)(HR³Sn)₂Se₄Cl] ( 6 ), in which R¹=CMe₂CH₂C(O)Me, R²=CMe₂CH₂C(NNH₂)Me, and R³=CH₂CH₂COO, are based on defect heterocubane scaffolds, as shown by X‐ray diffraction, ¹¹⁹Sn NMR spectroscopy, and ESI mass spectrometry analyses. Compounds 4 , 5 , and 6 constitute the first examples of defect heterocubane‐type metal‐chalcogenide complexes that are comprised of selenide ligands. Comprehensive DFT calculations prompted us to search for the formal intermediates [(R¹SnCl₂)₂(μ‐S)] ( 7 ) and [(R¹SnCl)₂(μ‐S)₂] ( 8 ), which were isolated and helped to understand the stepwise formation of compounds 1 – 6 .     

Preparation of Solid,Substituted Allylic Zinc Reagents and Their Reactions with Electrophiles

The treatment of various allylic chlorides or bromides with zinc dust in the presence of lithium chloride and magnesium pivalate (Mg(OCOtBu)₂) in THF affords allylic zinc reagents which, after evaporation of the solvent, produce solid zinc reagents that display excellent thermal stability. These allylic reagents undergo Pd‐catalyzed cross‐coupling reactions with PEPPSI‐IPent, as well as highly regioselective and diastereoselective additions to aryl ketones and aldehydes. Acylation with various acid chlorides regioselectively produces the corresponding homoallylic ketones, with the new C? C bond always being formed on the most hindered carbon of the allylic system.     

Diazoalkane complexes of tungsten from the condensation of hydrazido Complexes with Ketones

Hydrazido(2?) and hydrazido(1?) complexes of tungsten condense with ketones, R¹R²CO, in the presence of catalytic amounts of acid to yield complexes containing the groups W = NN = CR¹R² and WNHN =CR¹R² respectively. The other ligands are halide ions and monotertiary phosphines. These new complexes yield secondary amines and ammonia on reduction with LiAlH₄; acids produce nitrogen-free tungsten materials, hydrazine and azines.     

Synthesis of pyridine N-imine complexes of methylcobaloxime and reactions of bis(dimethylglyoximato)methyl(Pyridine N-imine)cobalt with acid anyhydrides and acetylenedicarboxylic acid dimethyl ester

Pyridine N-imine complexes of methylcobaloxime, CH₃Co(Hdmg)₂(R¹— C₅H_nN⁺N^?H) (n = 4; R¹ = H, 2-CH₃, 3-CH₃, 4-CH₃: n = 3; R¹ = 2,6-CH₃), have been synthesized by the reaction of CH₃Co(Hdmg)₂S(CH₃)₂ with a pyridine N-imine which is generated from a pyridine, hydroxylamine-O-sulfonic acid and K₂CO₃. The reactions of CH₃Co(Hdmg)₂(C₅H₅N⁺N^?H) with acid anhydrides form new methylcobaloxime complexes with N-substituted pyridine N-imines, CH₃Co(Hdmg)₂(C₅H₅N⁺N^?R²) R² = COPh, COMe, COEt). With maleic anhydride, (pyridine N-acryloylimine)carboxylic acid is formed. With acetylenedicarboxylic acid dimethyl ester, 1,3-dipolar cycloaddition of the ligand gives pyrazolo[1,5-a]pyridine-2,3-dicarboxylic acid dimethyl ester.     

Pd complexes of iminophosphine ligands: A homogeneous molecular catalyst for Suzuki–Miyaura cross-coupling reactions under mild conditions

The complexes formed by combining Pd(OAc)₂ and iminophosphine ligands (P^N) are active catalysts in Suzuki–Miyaura cross-coupling reactions under mild conditions. Aryl bromides and iodides, as well as benzyl chlorides give the corresponding coupled products in high yields at low temperatures (25–50 °C) using these catalysts. Iminophosphines containing the most sterically demanding groups attached to the N-imino moiety were the most effective ligands. New divalent Pd complexes of known iminophosphines were synthesised and their activity was compared with the in situ generated catalyst system. The complex resulting from the oxidative addition of 4-bromo anisole [Pd(4-CH₃OC₆H₄)Br(P^N)] was more active than the in situ generated system. However, palladacycles containing the iminophosphine ligand (e.g., {[C₆H₄CH(Me)₂St-Bu]Pd(P^N)}⁺PF₆⁻) were less active than the in situ generated catalyst due to the greater stability of the complexes that involve two bidentate ligands. Poisoning tests demonstrated that homogeneous mononuclear palladium species containing the iminophsophine ligand were responsible for the catalytic activity.     

Oxidative dehydrogenation of N-(2-hydroxy-3,5-R<Superscript>1</Superscript>,R<Superscript>2</Superscript>-benzyl)-4-aminoantipyrines in the complexation reaction

Reactions of N-(2-hydroxy-3,5-R¹,R²-benzyl)-4-aminoantipyrines with copper acetate in ethanol gave complexes with Schiff bases (SBs) rather than the expected complexes with reduced SBs; i.e., the starting ligands undergo oxidative dehydrogenation during the complexation reaction. The corresponding complexes with reduced SBs were obtained from sodium salts of the ligands and cupric sulfate in aqueous solutions. Kinetic measurements showed that oxidative dehydrogenation occurs in the heteroleptic complexes Cu(L ⁱ )(CH₃COO)(X) (L ⁱ H are derivatives of N-(2-hydroxy-3,5-R¹,R²-benzyl)-4-aminoantipyrines; i = 6–10; X = H₂O, CH₃OH, CH₃CH₂OH) but does not occur in the complexes CH₃OH, CH₃CH₂OH. The absence of oxidative dehydrogenation of the ligands in Cu(L ⁱ )₂ · H₂O can be explained by the octahedral environment of the Cu²⁺ ion and, accordingly, the absence of the coordination site for molecular oxygen. The molecular structures of two Cu(II) complexes with SBs were determined by X-ray diffraction.     

Convenient synthesis of highly optically active 2,3,4,6-tetrasubstituted tetrahydropyrans via Prins cyclization reaction (PCR) of optically active homoallylic alcohols with aldehydes

Prins cyclization reaction (PCR) of optically active homoallylic alcohols, R^aC^*H(OH)CH₂CHCHCH₃ (1-substituted but-2-en-1-ol), with aldehydes (R^bCHO) in the presence of an acid-catalyst (HX) affords (2-R^b,3-CH₃,4-X,6-R^a)-tetrasubstituted tetrahydropyrans highly stereoselectively in good yields.     

Koordinationschemische Untersuchungen an Zinkdialkylen. XIV. Über Lithium- und Zink-3-(N,N-dialkylamino)-propyl-Verbindungen

Investigations on the Coordination Chemistry of Zinc Dialkyls. XIV. On Lithium and Zinc 3(N, N-Dialkylamino)propyl Compounds It is reported on synthesis and properties of organo lithium compounds of the type [R₂NCH₂CH₂CH₂Li]_n. The structure is proposed by reason of molecular weight determination and ¹³C-NMR spectra. In dependence of the molar ratio the lithium dialkylamino propyls and the corresponding Grignard reagents react with zinc chloride forming dimer alkyl zinc chlorides [R₂NCH₂CH₂CH₂ZnCl]₂ or monomer spiranoide chelate complexes of the formula [R₂NCH₂CH₂CH₂]₂Zn (R = CH₃, C₂H₅).     

Synthesis,Properties, and Structures of Chromium(VI) and Chromium(V) Complexes with Heterocyclic Nitrogen Ligands

The reaction of CrO₂Cl₂ with 2, 2′‐bipyridyl or 1, 10‐phenanthroline (diimine) in CCl₄ or anhydrous CH₃CO₂H solution, produces orange‐brown diamagnetic [CrO₂Cl₂(diimine)]. The X‐ray structure of [CrO₂Cl₂(2, 2′‐bipy)] shows a six‐coordinate central chromium(VI) atom with cis‐dioxo groups trans to the diimine. In contrast, the diimines react with CrO₃ in CH₃CO₂H / conc. aqueous HCl to form bright red paramagnetic Cr^V complexes, [CrOCl₃(diimine)]. The X‐ray structure of [CrOCl₃(2, 2′‐bipy)] shows a six‐coordinate central chromium atom with mer‐chlorines and the diimine trans to O/Cl. The addition of [2, 2‐bipyH₂]Cl₂ to a solution of CrO₃ in CH₃CO₂H saturated with HCl gas, produces the Cr^V anion [2, 2′‐bipyH₂][CrOCl₄]Cl, which loses HCl on heating in vacuo to form [CrOCl₃(2, 2′‐bipy)]. IR, UV/Vis, and ¹H NMR spectra (Cr^VI only) are reported for the new complexes. Attempts to extend these routes to oxygen donor ligands, including ethers and phosphine oxides, were unsuccessful. The diimine complexes are the first structurally autheticated adducts of chromium(VI) and (V) oxide‐chlorides with neutral ligands.     

Diphosphine Compounds,Part III: UV/Visible Spectroscopy and Novel Routes to Functionalized Diphosphine-M(CO)6 Complexes (M = W,Mo, or Cr)

Reaction of coordinated (diphenylphosphino)methane and ketones or aldehydes have been characterized by ³¹P{H¹}-NMR, ¹H{³¹P}-NMR, and UV/vis spectroscopy in dichloromethane. Group VI metals hexacarbonyl [M(CO)₆ where M = Cr, Mo, and W] reacted with (diphenylphosphino)methane, [(Ph₂P)₂CH₂], to give [(OC)₄M{(Ph₂P)₂CH₂}] depending upon the reaction conditions. Condensation of [(CO)₄M{(Ph₂P)₂CH₂}] with different ketones or aldehydes forms [(CO)₄M{(Ph₂P)₂C = CR₁R₂}]. Complexes of the types [(OC)₄M{(Ph₂P)₂C = CR₁R₂}] reacted with hydrazine in a Michael addition to give [(CO)₄M{(Ph₂P)₂CHC(R₁R₂)NHNH₂}](1.3a–e), which condensed with different ketones and aldehydes to give complex of the type [(CO)₄M{(Ph₂P)₂CHC(R₁R₂)NHN = C(R₃)] (1.4a–e). The structures of the complexes are discussed on the basis of elemental analysis (EA), IR,¹H-NMR, ³¹P-NMR spectroscopic data, and FAB mass spectra. The UV/vis spectra show two absorption bands with the low energy band moving to lower energy with increasing substitution on the (diphenylphosphino) methane (dppm) (a bathochromic effect).     

Low-Coordinate Monomeric Zinc Hydride Complexes with Encapsulating Dipyrromethene Ligands and Reactivity with B(C6F5)3

The dipyrromethene (DPM) ligand is the key to isolation of monomeric Zn hydride complexes with tricoordinate zinc centers. A range of ^RDPM ligands with various substituents in the pole position (1,9-positions) were prepared: R = tBu, adamantyl (Ad), mesityl (Mes), 2,6-diisopropylphenyl (DIPP), 2,4,6-triphenylphenyl (Mes*), or 9-anthracenyl (Anth). Reaction of the ligands with Et₂Zn gave a series of (^RDPM)ZnEt complexes, which were converted with I₂ to the corresponding (^RDPM)ZnI compounds. The latter reacted by salt metathesis with KN(iPr)HBH₃ to the series of Zn hydride complexes (^RDPM)ZnH. For ligands with the larger Mes* and Anth substituents, (^RDPM)ZnEt was converted to (^RDPM)ZnOSiPh₃, which after reaction with PhSiH₃ gave the hydrides. While Zn hydride complexes with R = tBu or Ad are dimeric, all complexes with aryl-substituents are monomeric. The aryl groups span a cavity around the metal, blocking dimerization and causing a high-field shift of the ¹H NMR signals due to the ASIS effect. Attempted abstraction of the hydride with B(C₆F₅)₃ led to cleavage of the B-C₆F₅ bond.     

Unusual reactivity of a quasi-aromatic Ni(II),2N,3C heterocycle

[Ni(PnAO)-6H]^o, a Ni,2N,3C-pseudoaromatic heterocycle is shown to be highly reactive at the central carbon atom toward most aldehydes and ketones, giving with CH₂O, for example, a dimer having the formula [Ni(PnAO)-7H]₂-CH₂ whose X-ray crystal structure as well as ¹³C and ¹H NMR spectra are presented.     

CC Coupling of N‐Heterocycles at the fac‐Re(CO)3 Fragment: Synthesis of Pyridylimidazole and Bipyridine Ligands

A new family of cationic rhenium tricarbonyl complexes with either two N‐alkylimidazole (N‐RIm) and one pyridine (Py) ligand, or two pyridine and one N‐RIm ligand, [Re(CO)₃(N‐RIm)_(3?x)(Py)_x]⁺, has been prepared. The reaction of these complexes with a strong base, followed by an oxidant, selectively afforded 2,2’‐pyridylimidazole complexes as the result of intramolecular dehydrogenative C?C coupling reactions. For tris(pyridine) complexes [Re(CO)₃(Py)₃]⁺ the reaction pattern upon a deprotonation/oxidation sequence is maintained, which allows the generation of complexes with 2,2’‐bipyridine ligands. In the particular combination of two different types of pyridine ligand in the cationic fac‐Re(CO)₃ complexes only the cross‐coupling products with asymmetric 2,2’‐bipyridine ligands were obtained; the homocoupling products were not observed.     

Recent Chemistry Based on the [RuCp(CH3CN)3]+ Cation: Reappraisalof an Old Precursor

 This article gives an overview of recent chemistry based on the tris-acetonitrile complex [RuCp(CH₃CN)₃]⁺. Due to the labile nature of the CH₃CN ligands, substitution reactions are a dominant feature of this complex. Important derivatives are the highly reactive complexes [RuCp(PR ₃)(CH₃CN)₂]⁺ which are a source of the 14e⁻ fragment [RuCp(PR ₃)]⁺. These species are catalytically active in the redox isomerization of allyl alcohols to give aldehydes and ketones. Furthermore, the cationic complex [RuCp(κ¹(P),η²-PPh₂CH₂CH₂CH*CH₂)(CH₃CN)]PF₆ derived from the reaction of [RuCp(CH₃CN)₃]⁺ with PPh₂CH₂CH₂CH*CH₂ is a model compound for studying coupling reactions of olefins and acetylenes. In addition, [RuCp(CH₃CN)₃]⁺ is a valuable precursor for the synthesis of configurationally stable chiral three-legged piano-stool ruthenium complexes. These are currently being intensively investigated as Lewis acid catalysts in asymmetric synthesis.     

Synthesis of novel zirconium complexes bearing mono‐Cp and tridentate Schiff base [ONO] ligands and their catalytic activities for olefin polymerization

A series of novel zirconium complexes {R²Cp[2‐R¹‐6‐(2‐CH₃OC₆H₄N?CH)C₆H₃O]ZrCl₂ ( 1 , R¹ = H, R² = H, 2 : R¹ = CH₃, R² = H; 3 , R¹ = ^tBu, R² = H; 4 , R¹ = H, R² = CH₃; 5 , R¹ = H, R² = n‐Bu)} bearing mono‐Cp and tridentate Schiff base [ONO] ligands are prepared by the reaction of corresponding lithium salt of Schiff base ligands with R²CpZrCl₃·DME. All complexes were well characterized by ¹H NMR, MS, IR and elemental analysis. The molecular structure of complex 1 was further confirmed by X‐ray diffraction study, where the bond angle of Cl? Zr? Cl is extremely wide [151.71(3)°]. A nine‐membered zirconoxacycle complex Cp(O? 2? C₆H₄N?CHC₆H₄‐2? O)ZrCl₂ ( 6 ) can be obtained by an intramolecular elimination of CH₃Cl from complex 1 or by the reaction of CpZrCl₃·DME with dilithium salt of ligand. When activated by excess methylaluminoxane (MAO), complexes 1–6 exhibit high catalytic activities for ethylene polymerization. The influence of polymerization temperature on the activities of ethylene polymerization is investigated, and these complexes show high thermal stability. Complex 6 is also active for the copolymerization of ethylene and 1‐hexene with low 1‐hexene incorporation ability (1.10%). Copyright © 2006 John Wiley & Sons, Ltd.