Hydroxylation of azomethine carbon: isolation of complexes of η5 and η6-cyclic hydrocarbon platinum group metals with a new Schiff-base ligand

A new Schiff base, (pyridin-2-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine, (L), was synthesized. Reaction of [(η⁶-arene)Ru(µ-Cl)Cl]₂ and [Cp*M(µ-Cl)Cl]₂ (M = Rh and Ir) with one equivalent of L in the presence of NH₄PF₆ in methanol yielded dinuclear complexes, [(η⁶-arene)₂Ru₂(L-OH)Cl](PF₆)₂ {arene = C₆H₆ (1), p-ⁱPrC₆H₄Me (p-cymene) (2) and C₆Me₆ (3)}, and [Cp*₂M₂(L-OH)Cl](PF₆)₂ [M = Rh (4) and Ir (5)], respectively, leading to the formation of five new chiral complexes with –OH on the azomethine carbon. L is a pentadentate ligand where one of the metal centers is coordinated to two nitrogen atoms in a bidentate chelating fashion while the other metal is bonded tridentate to three nitrogen atoms. Although the ligand is neutral before coordination, after complexation it is anionic (uni-negative) with negative charge on the azo nitrogen {see the structures: N(5) in 2[PF₆]₂ and N(3) for 4[PF₆]₂}. The complexes have been characterized by various spectroscopic methods including infrared and ¹H NMR and the molecular structures of the representative complexes are established by single-crystal X-ray diffraction studies.     

Synthesis and characteristic of double hydrophilic block copolymer with amine pendant chains

Novel double hydrophilic block copolymers with amine pendant chains were synthesized by polymerization of 4-vinyl benzylamine hydrochloric salt using 4,4′-azo-bis[4-cyanopentanoate poly（ethylene glycol） ester] as macroazoinitiator. The structures of the copolymers were characterized by ^1H NMR, FTIR spectra and acid-base titration, GPC-MALS techniques.     

Study of novel η-cyclopentadienyl and η-arene platinum group metal complexes containing a N4-type ligand and their structural characterization

The mononuclear η⁵-cyclopentadienyl complexes [(η⁵-C₅H₅)Ru(PPh₃)₂Cl], [(η⁵-C₅H₅)Os(PPh₃)₂Br] and pentamethylcyclopentadienyl complex [(η⁵-C₅Me₅)Ru(PPh₃)₂Cl] react in the presence of 1 eq. of the tetradentate N,N′-chelating ligand 3,5-bis(2-pyridyl)pyrazole (bpp-H) and 1 eq. of NH₄PF₆ in methanol to afford the mononuclear complexes [(η⁵-C₅H₅)Ru(PPh₃)(bpp-H)]PF₆ ([1]PF₆), [(η⁵-C₅H₅)Os(PPh₃)(bpp-H)]PF₆ ([2]PF₆) and [(η⁵-C₅Me₅)Ru(PPh₃)(bpp-H)]PF₆ ([3]PF₆), respectively. The dinuclear η⁵-pentamethylcyclopentadienyl complexes [(η⁵-C₅Me₅)Rh(μ-Cl)Cl]₂ and [(η⁵-C₅Me₅)Ir(μ-Cl)Cl]₂ as well as the dinuclear η⁶-arene ruthenium complexes [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂ and [(η⁶-p-ⁱPrC₆H₄Me)Ru(μ-Cl)Cl]₂ react with 2 eq. of bpp-H in the presence of NH₄PF₆ or NH₄BF₄ to afford the corresponding mononuclear complexes [(η⁵-C₅Me₅)Rh(bpp-H)Cl]PF₆ ([4]PF₆), [(η⁵-C₅Me₅)Ir(bpp-H)Cl]PF₆ ([5]PF₆), [(η⁶-C₆H₆)Ru(bpp-H)Cl]BF₄ ([6]BF₄) and [(η⁶-p-ⁱPrC₆H₄Me)Ru(bpp-H)Cl]BF₄ ([7]BF₄). However, in the presence of 1 eq. of bpp-H and NH₄BF₄ the reaction with the same η⁶-arene ruthenium complexes affords the dinuclear salts [(η⁶-C₆H₆)₂Ru₂(bpp)Cl₂]BF₄ ([8]BF₄) and [(η⁶-p-ⁱPrC₆H₄Me)₂Ru₂(bpp)Cl₂]BF₄ ([9]BF₄), respectively. These compounds have been characterized by IR, NMR and mass spectrometry, as well as by elemental analysis. The molecular structures of [1]PF₆, [5]PF₆ and [8]BF₄ have been established by single crystal X-ray diffraction studies and some representative complexes have been studied by UV–vis spectroscopy.     

Reactions of chelated η-pentadienyl iron complexes with nucleophiles

Ferracyclic (1-3-η³)pentadienyl complexes with electronically decoupled allyl and vinyl moieties were reacted with various heteroatom and carbon nucleophiles. Primary amines selectively attacked neutral (4-6-η³-pentadienyl)ferralactones 2 on the end of the allyl ligand to give 3-(endo-vinyl)-(4-6-η³-allyl)ferralactams 4 and by a similar reaction of the latter eventually 6-(exo-vinyl)-(4-6-η³-allyl)ferralactams 5. -like attack on the conjugated coplanar vinyl residue of 2 was not observed. The cationic η³-allyl complex 3 was attacked by nucleophiles either on the allylic terminus furnishing free (1Z, 3E)-dienes 8, or on the vinyl residue which is part of an activated Michael system to give η⁴-1,3-diene complexes 9. η⁴-1,3,5-Triene complex 10 was obtained with basic nucleophiles.     

How big is a Cp? Cycloheptatrienyl zirconium complexes with bulky cyclopentadienyl and indenyl ligands

A combination of phase-transfer and traditional alkylation strategies has been employed to synthesise sterically encumbered 1,3-di(cyclohexyl) and 1,3-di(tert-butyl) substituted indenes in multi-gram quantities. These indenyl ligands and sterically demanding alkyl cyclopentadienyl ligands have been used to prepare a series of [(η(7)-C(7)H(7))Zr(η(5)-L)] (L = Cp and Ind) complexes by straightforward salt metathesis between [(η(7)-C(7)H(7))ZrCl(tmeda)] and the corresponding sodium indenide or cyclopentadienide. All of these Zr complexes have been characterized by elemental analysis, NMR spectroscopy and single crystal X-ray diffraction. The structural information derived from these studies was employed to evaluate the steric demand of these ligands in a realistic manner.     

η-Arene complexes of ruthenium and osmium with pendant donor functionalities

Conversion of 4′-(2,5-dihydrophenyl)butanol or N-trifluoroacetyl-2,5-dihydrobenzylamine with MCl₃·n H₂O (M = Ru, Os) affords the corresponding dimeric η⁶-arene complexes in good to excellent yields. Under similar reaction conditions, the amine functionalized arene precursor 2,5-dihydrobenzylamine yields the corresponding Ru(II) complex. For osmium, HCl induced oxidation leads to formation of [OsCl₆]²⁻ salts. However, under optimized reaction conditions, conversion of the precursor 2,5-dihydrobenzylamine chloride results in clean formation of η⁶-arene Os(II) complex. X-ray structures of [(η⁶-benzyl ammonium)(dmso)RuCl₂] and (2,5-dihydrobenzyl ammonium)₄[OsCl₆]₂confirm the spectroscopic data. High stability towards air and acid as well as enhanced solubility in water is observed for all η⁶-arene complexes.     

Synthesis and properties of group 9 metal complexes bearing a β-ketophosphenato ligand

A novel β-ketophosphenato ligand bearing a bulky substituent, Tbt(2,4,6-tris[bis(trimethylsilyl)methyl]phenyl), on the phosphorus atom was newly designed and synthesized as a heavier congener of a β-ketoiminato ligand. Rhodium and iridium complexes bearing this new β-ketophosphenato ligand have been synthesized and fully characterized by spectroscopic and elemental analyses together with X-ray crystallographic analyses. The results of NMR spectroscopic studies and the X-ray structural analyses suggested that the β-ketophosphenato ligand has unique electronic features due to the low-coordinated phosphorus atom. Comparison of properties between rhodium β-ketophosphenates 2a,b and rhodium β-ketoiminate 7 revealed the character of the β-ketophosphenato ligand, where the trans influence of the phosphorus atom should be stronger than the nitrogen atom of the β-ketoiminato ligand.     

Synthesis and complexation of a new 1,1′-disubstituted ferrocene with two pendant chelating sites of an α,β-unsaturated β-keto amine subunit

Condensation of 1,1′-bis(aminomethyl) ferrocene with acetylacetone gave 1,1′ -bis(3 - methyl - 5 - oxo - 2 - aza - 3 - hexenyl)ferrocene in a 56% yield. In chloro-bridge splitting reactions of dinuclear cyclopalladated complexes of benzo[h] quinoline and NN-dimethylbenzylamine, the condensed compound served as a binucleating ligand of an α,β-unsaturated β-keto aminate subunit. These new compounds formed were characterized by means of ¹H and ¹³C NMR and IR spectroscopy. Their electrochemical properties were discussed also.     

Synthesis, spectroscopy and biological investigations of manganese(III) Schiff base complexes derived from heterocyclic β-diketone with various primary amine and 2,2'-bipyridyl

The mixed ligand mononuclear complex [Mn(bipy)(HPMFP)(OAc)]ClO(4) was synthesized by reaction of Mn(OAc)(3)·2H(2)O with HPMFP and 2,2'-bipyridyl. The corresponding Schiff base complexes were prepared by condensation of [Mn(bipy)(HPMFP)(OAc)]ClO(4) with ethylenediamine, ethanolamine and glycine (where HPMFP=1-phenyl-3methyl-4-formyl-2-pyrazolin-5one, bipy=2,2'-bipyridyl). All the compounds have been characterized by elemental analysis, magnetic susceptibility, conductometry measurements and (1)H and (13)C NMR, FT-IR, mass spectrometry. Electronic spectral and magnetic susceptibility measurements indicate square pyramidal geometry around manganese(III) ion. The thermal stabilities, activation energy E*, entropy change ΔS*, enthalpy change ΔH* and heat capacity of thermal degradation for these complexes were determined by TGA and DSC. The in vitro antibacterial and antifungal activity of four coordination compounds and ligand HPMFP were investigated. In vitro activates of Bacillus subtillis (MTCC-619), Staphylococcus aureus (MTCC-96), Escherichia coli (MTCC-722) and Klebsiella pneumonia (MTCC-109) bacteria and the fungus Candida albicans (ATCC-90028) were determined. All the compounds showed good antimicrobial activity. The antimicrobial activities increased as formation of Schiff base.     

Enantioselective aldol reactions of α,β-unsaturated ketones with trifluoroacetophenone catalyzed by a chiral primary amine

Chiral primary amine catalyzed direct asymmetric aldol reactions of ketones with trifluoroacetophenone, afforded trifluoromethylated β-hydroxycarbonyl aldol products bearing a quaternary carbon stereogenic center in high yields (up to 93% yield) and with high to excellent enantioselectivities of up to 99% ee.     

Reaction of metal carbonyl anions with electrophilic alkynes: Synthesis of isomeric η-acryloyl and σ-vinyl complexes

Treatment of the metal carbonylate anions [CpMo(CO)₂(L)]⁻ (Cp = η-C₅H₅; L = PPh₂Me, PPh₂Et) with the electrophilic alkynes methyl propiolate or DMAD (RCCCO₂Me, where R = H or CO₂Me, respectively) followed by protonation affords the η³-acryloyl (1-oxoallyl) complexes [CpMo(η³-COCRCHCO₂Me)(CO)(L)] (3a-d) as the major products, together with the isomeric vinyl complexes trans-[CpMo(CRCHCO₂Me)(CO)₂(L)] (4a-d). On the basis of the regioselectivity of the reaction, it is proposed that nucleophilic attack of the carbonylate anion occurs at the alkyne carbon bearing R; migration of the anionic vinyl ligand to a CO followed by protonation gives 3, whereas protonation without insertion gives 4. The X-ray structures of the acryloyl complex [CpMo(η³-COCHCHCO₂Me)(CO)(PPh₂Me)] (3b) and its vinyl isomer [CpMo(σ-CHCHCO₂Me)(CO)₂(PPh₂Me)] (4b) have been determined.     

The synthesis and characterization of organometallic copolymers with Mn-Re binuclear transition-metal group in the side chain

Novel organometallic copolymers with Mn-Re binuclear transition-metal groups in the side chain are synthesized and characterized. The structure and properties of the copolymers are characterized by GPC, DSC, TG, NMR, FT-IR, UV-Vis spectra and elemental analysis. The glass transition temperature and UV-Vis spectra properties of these three organometallic copolymers are found to be different from the normal polystyrene. New synthetic strategy for the synthesis of or-ganometallic copolymer is developed.     

Synthesis of 2-picolyl functionalized η-cyclopentadienyl derivatives of rhodium(I) and iridium(I) and preliminary study of their reaction with ruthenium(II) for assembling hetero-bimetallic complexes

The 2-picolylcyclopentadienyl derivatives of rhodium(I) and iridium(I) of formula [M{η⁵-C₅H₄(2-CH₂C₅H₄N)}(η⁴-C₈H₁₂)] (3) (M = Rh) and (4) (M = Ir) are obtained in good yields by reacting 2-picolylcyclopentadienyllithium (7) with [RhCl(η⁴-C₈H₁₂)]₂ and [IrCl(η⁴-C₈H₁₂)]₂, respectively. The corresponding dicarbonyl derivatives, [M{η⁵-C₅H₄(2-CH₂C₅H₄N)}(CO)₂] (5) (M = Rh) and 6 (M = Ir), are obtained in good yields by reacting 2-picolylcyclopentadienylthallium(I) (8) with [RhCl(CO)₂]₂ and [IrCl(C₅H₅N)(CO)₂], respectively. 5 has already been reported in the literature. The new complexes were characterized by elemental analysis, mass spectrometry, ¹H NMR, FT-IR, and UV-Vis (210-330 nm) spectroscopy. The UV-Vis spectra indicate the existence of some electronic interaction between the 2-picolinic chromophore and the cyclopentadienyl-metal moiety. The study of the electrochemical behaviour of 3-6 by cyclic voltammetry (CV) allows the interpretation of the electrode processes and gives information about the location of the redox sites. Moreover, various synthetic strategies were tested in order to try to coordinate the complexes 3-6 to a ruthenium(II) centre, but most of them failed. Instead, the hetero-bimetallic complex bis(2,2′-bipyridine)[(η⁵-2-picolylcyclopentadienyl)(η⁴-cycloocta-1,5-diene)rhodium(I)]chlororuthenium(II)-(hexafluorophosphate) (13), was obtained, although in poor yields (10%), by reacting the nitrosyl complex [RuCl(bipy)₂(NO)][PF₆]₂14 (bipy = 2,2′-bipyridine) first with potassium azide and then with the rhodium(I) complex 3. The analogous complex bis(2,2′-bipyridine)(2-picoline)chlororuthenium(II)-(hexafluorophosphate) (15), that carries a ruthenium-bonded 2-picoline molecule instead of 3, has prepared in the same way. 13 and 15 were characterized by elemental analysis, mass spectrometry, and ¹H NMR.     

Cyclometallated thiosemicarbazone palladium(II) compounds: The first crystal and molecular structures of mononuclear complexes with a η-diphosphine ligand

Treatment of the thiosemicarbazones 2-XC₆H₄C(Me)NN(H)C(S)NHR (R = Me, X = F, a; R = Et, X = F, b; R = Me, X = Cl, c; R = Et, X = Br, d) with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid, as appropriate, gave the tetranuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}]₄ (1a-1d). Reaction of 1a-1d with the diphosphines Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH₂)₃PPh₂ (dppp) or trans-Ph₂PCHCHPPh₂ (trans-dpe) in 1:2 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-XC₆H₃C(Me)NNC(S)-NHR]}₂(μ-diphosphine-P,P)] (2a-5a, 3b, 3d, 4c, 5c). Reaction of 1a, 1b with the short-bite or long-bite diphosphines, dppm or cis-dpe, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}(diphosphine-P)] (6a, 6b, 7a). The molecular structure of ligand a and of complexes 1a, 3d, 5a, 5c, 6a, 6b and 7a have been determined by X-ray diffraction analysis. The structure of complex 7a shows that the long-bite cis-bis(diphenylphosphino)ethene phosphine appears as monodentate with an uncoordinated phosphorus donor atom.     

Synthesis and characterization of a monomeric and a dihydroxo-bridged dimeric complexes of iron(III) with α-benzoinoxime

The reaction of α-benzoinoxime, H₂BNO with FeCl₃ in the presence of Et₃N as a base gives the mononuclear Fe(III) complex, Fe(HBNO)₃ (1). Treatment of 1 with a methanolic solution of KOH at room temperature leads to a dinuclear Fe(III)–Fe(III) complex, [Fe(HBNO)₂OH]₂ (2). The complexes were initially characterized on the basis of their elemental, mass and thermal analyses. The IR studies were useful in assigning the coordination mode of the benzoinoxime ligand to the iron metal. In addition, the presence of a hydroxo-bridge in the dimeric complex 2 is inferred from the IR spectral studies. Room-temperature Mössbauer studies indicated octahedral, high-spin iron(III). Variable-temperature magnetic susceptibility measurements supported the existence of the μ-dihydroxo-bridging structure core, Fe^III(μ-OH)₂Fe^III in the dinuclear complex 2. Theoretical modelling of the magnetic data indicated a weak antiferromagnetic spin exchange between the iron(III) centers (J = −8.35 cm⁻¹, g = 2.01, ρ = 0.02 and TIP = 1.7 × 10⁻⁴ cm³ mol⁻¹ for H = −2JS₁ · S₂). The electronic spectra of the complexes revealed two bands due to d–d transitions and one band assignable to an oxygen (p_π) → Fe(d_π∗) LMCT transition observed in each complex. An additional charge-transfer transition, assignable to μ-hydroxo(p_π) → Fe(d_π∗), was observed for the dimeric complex 2. The structural and vibrational behaviors of these complexes have been elucidated with quantum mechanical methods.     

Preparation and characterization of Cp-functionalized cycloheptatrienyl–cyclopentadienyl titanium sandwich complexes (troticenes)

Cp-functionalized monotroticenes [(η⁷-C₇H₇)Ti(η⁵-C₅H₄E)] (2, E = Ph₂SiCl; 3, E = tBu₂SnCl; 12, E = I) and bitroticenes [(η⁷-C₇H₇)Ti(η⁵-C₅H₄)]₂E′ (5, E′ = PPh; 6, E′ = BN(SiMe₃)₂; 7, E′ = Cp₂Ti) were prepared by salt elimination metathesis between the monolithiated troticene [(η⁷-C₇H₇)Ti(η⁵-C₅H₄Li)]·pmdta (1b) (pmdta = N,N′,N′,N″,N″-pentamethyldiethylene-triamine) and the appropriate electrophile. The troticenyl-substituted zirconocene monochloride [(η⁷-C₇H₇)Ti(η⁵-C₅H₄ZrClCp*₂)] (Cp* = η⁵-C₅Me₅) (8) and hafnocene ethoxide [(η⁷-C₇H₇)Ti{η⁵-C₅H₄Hf(OEt)Cp₂}] (Cp = η⁵-C₅H₅) (11), and the heterobimetallic μ-oxo complexes [(η⁷-C₇H₇)Ti(η⁵-C₅H₄MCp₂)]₂O (9, M = Zr; 10, M = Hf) were obtained instead of the expected zircona- and hafna[1]troticenophanes by reaction of the dilithiated troticene [(η⁷-C₇H₆Li)Ti(η⁵-C₅H₄Li)]·pmdta (1a) with [Cp₂MCl₂] (M = Zr, Hf) or [Cp*₂ZrCl₂] in stoichiometric amounts. These compounds were characterized by single crystal X-ray diffraction analyses and, in the case of 2, 3, 5–7, 9, 10 and 12, also by elemental analyses and ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. Exposure of the troticenyl organotin chloride 3 to moisture resulted in its partial hydrolysis and formation of the organostannoxane-bridged bitroticene 4, while palladium-catalyzed Negishi C–C cross-coupling reaction between the troticenylzinc chloride [(η⁷-C₇H₇)Ti(η⁵-C₅H₄ZnCl)] (13) and the iodotroticene 12 or iodobenzene (PhI) led to the fulvalene complexes [(η⁷-C₇H₇)Ti(η⁵-C₅H₄)]₂ (14) and [(η⁷-C₇H₇)Ti(η⁵-C₅H₄Ph)] (15). Compound 4 displays an unsymmetrical structure with the troticenyl fragments cis with respect to the Sn–O–Sn core, whereas compound 14 is centrosymmetrically trans oriented.     

Substitution reaction of η5-cyclopentadienylruthenium(II) complexes with nitrogen,oxygen and sulfur donor ligands

The heterocycles pyridine, γ-picoline, 2,2′-bipyridine and 1,10-phenanthroline react with [(η⁵-C₅H₅)Ru(MPh₃)₂X] (M = P, As or Sb) and [(η⁵-C₅H₅)Ru(AsPh₃)(PPh₃)X] (X = Cl, Br, I, CN, NCS or SnCl₃) to form complexes of types [(η⁵-C₅H₅)(MPh₃)(L−L)⁺X⁻ (L−L = 2,2′−bipyridine or 1,10−phenanthroline; X = Cl, Br, I, CN, NCS or SnCl₃) and [(η⁵-C₅H₅)Ru(MPh₃)LX] (M = As or Sb; L = pyridine or γ-picoline; X = Cl, Br, I, CN, NCS or SnCl₃). Interactions of dithiocarbamate (DTC) with [(η⁵-C₅H₅)Ru(SbPh₃)₂X] (X = Cl, Br or I) and acetylacetonate (acac) with parent compounds [(η⁵-C₅H₅)Ru(MPh₃)₂X (M = P or Sb; X = Cl, Br or I) yielded [(η⁵-C₅H₅)Ru(MPh₃)L] (where L = DTC or acac). The reaction products have been characterized by magnetic, spectral and microanalytical data.     

Host–guest complexation of antioxidative caffeic and ferulic acid amides with a functionalized cyclophane

Host?guest complexation has been studied by ¹H NMR on the benzyl and phenethyl amides of ferulic and caffeic acids as the guests in chloroform and acetonitrile; the counter host is a cyclophane which integrates four phenylene rings, amino and amide groups in the macrocyclic framework and bears four pendant methyl acetate ester arms. CAPE, one of the best known natural antioxidants, also has been studied for comparison. Among the guests studied, ferulic acid benzyl amide shows NMR shifts due to the formation of a host?guest complex in chloroform. The complexation occurs in two steps with the formation constants K ₁?=?[HG]/[H][G]?=?6?M^?1 and β ₂?=?[HG₂]/[H][G]²?=?87?M^?2. Two guest molecules are bound on the surface of the macrocyclic framework of a host molecule by two hydrogen bonds, NH(host amide)···O=C(guest amide) and C=O(host ester)···HO(guest phenol). The latter hydrogen bond may protect the bioactive site, i.e., phenol OH, of guest molecules captured in the complex against undesirable oxidation. This feature is observed only for ferulic acid benzyl amide in chloroform; the cyclophane ester interacts with this amide, distinctively from the other hydroxycinnamic acid derivatives.     

The third-order NLO properties of D-π-A molecules with changing a primary amino group into pyrrole

The nonlinear refractive index, as well as the two-photon absorption (TPA), has been investigated by the femtosecond Z-scan method for push–pull molecules, in which a primary donor group is weakened by conversion into a pyrrole or related heterocycle. The results at the fast response time show that, contrary to what had been expected from a previous work, there is a little decrease in the nonlinear refractive index change by introduction of the weaker donor groups. Although the measured TPA spectra showed that the observed nonlinear refractive index change was regarded to be off-resonant; difference in the frequency dispersion among the molecules considerably contributes to the decrease, in addition to difference in the intrinsic static nonlinearity. This shows that there is some future in the development of these non-resonant materials.