Heterometallic clusters arising from cubic Ni3M′O4 (M′=K and Na) entity: Solvothermal synthesis with/without the assistance of microwave

Solvothermal reaction assisted with microwave leads to the formation of two unique heterometallic cubic clusters [Ni₃M′(L)₃(OH)(CH₃CN)₃]₂·CH₃CN (M′=K for 1 and M′=Na for 2, where L is an anion of 2-[(2-hydroxy-3-methoxy-benzylidene)-amino]-ethanesulfonate) with higher efficiency, yields and purity than those without it. The 6-metallacrown-3 [Ni₃(OH)(L)₃]⁻ groups exhibit interesting ion trapping and self-assembly of size-different Na⁺ and K⁺ through form recognition and coordination activity in 1 and 2. The magnetic studies for 1 and 2 suggest that the {Ni₃M′O₄} (M′=K and Na) cores both display dominant ferromagnetic interactions from the nature of the binding modes of μ₃-O (oxidophenyl) and μ₃-OH.     

Palladium acetate complexes bearing chelating N-heterocyclic carbene (NHC) ligands: Synthesis and catalytic oxidative homocoupling of terminal alkynes

The imidazolium salts 1,1′-dibenzyl-3,3′-propylenediimidazolium dichloride and 1,1′-bis(1-naphthalenemethyl)-3,3′-propylenediimidazolium dichloride have been synthesized and transformed into the corresponding bis(NHC) ligands 1,1′-dibenzyl-3,3′-propylenediimidazol-2-ylidene (L₁) and 1,1′-bis(1-naphthalenemethyl)-3,3′-propylenediimidazol-2-ylidene (L₂) that have been employed to stabilize the Pd^II complexes PdCl₂(κ²-C,C-L₁) (2a) and PdCl₂(κ²-C,C-L₂) (2b). Both latter complexes together with their known homologous counterparts PdCl₂(κ²-C,C-L₃) (1a) (L₃ = 1,1′-dibenzyl-3,3′-ethylenediimidazol-2-ylidene) and PdCl₂(κ²-C,C-L₄) (1b) (L₄ = 1,1′-bis(1-naphthalenemethyl)-3,3′-ethylenediimidazol-2-ylidene) have been straightforwardly converted into the corresponding palladium acetate compounds Pd(κ¹-O-OAc)₂(κ²-C,C-L₃) (3a) (OAc = acetate), Pd(κ¹-O-OAc)₂(κ²-C,C-L₄) (3b), Pd(κ¹-O-OAc)₂(κ²-C,C-L₁) (4a), and Pd(κ¹-O-OAc)₂(κ²-C,C-L₂) (4b). In addition, the phosphanyl-NHC-modified palladium acetate complex Pd(κ¹-O-OAc)₂ (κ²-P,C-L₅) (6) (L₅ = 1-((2-diphenylphosphanyl)methylphenyl)-3-methyl-imidazol-2-ylidene) has been synthesized from corresponding palladium iodide complex PdI₂(κ²-P,C-L₅) (5). The reaction of the former complex with p-toluenesulfonic acid (p-TsOH) gave the corresponding bis-tosylate complex Pd(OTs)₂(κ²-P,C-L₅) (7). All new complexes have been characterized by multinuclear NMR spectroscopy and elemental analyses. In addition the solid-state structures of 1b·DMF, 2b·2DMF, 3a, 3b·DMF, 4a, 4b, and 6·CHCl₃·2H₂O have been determined by single crystal X-ray structure analyses. The palladium acetate complexes 3a/b, 4a/b, and 6 have been employed to catalyze the oxidative homocoupling reaction of terminal alkynes in acetonitrile chemoselectively yielding the corresponding 1,4-di-substituted 1,3-diyne in the presence of p-benzoquinone (BQ). The highest catalytic activity in the presence of BQ has been obtained with 6, while within the series of palladium-bis(NHC) complexes, 4b, featured with a n-propylene-bridge and the bulky N-1-naphthalenemethyl substituents, revealed as the most active compound. Hence, this latter precursor has been employed for analogous coupling reaction carried out in the presence of air pressure instead of BQ, yielding lower substrate conversion when compared to reaction performed in the presence of BQ. The important role of the ancillary ligand acetate in the course of the catalytic coupling reaction has been proved by variable-temperature NMR studies carried out with 6 and 7′ under catalytic reaction conditions.     

Investigation of the zinc(II) acetylacetonate/benzotriazole reaction system in the presence of bridging N,N′-ligands: Pentanuclear, enneanuclear and polymeric complexes

The reaction of Zn(acac)₂ with btaH (1,2,3-benzotriazole) in dmf yielded the pentanuclear complex [Zn₅(bta)₆(acac)₄(dmf)]·dmf (1·dmf). In the presence of pyrazine, the pentanuclear [Zn₅(bta)₆(acac)₄(dmf)]·3.7dmf (2·3.7dmf) and enneanuclear [Zn₉(bta)₁₂(acac)₆]·6dmf (3·6dmf) complexes were formed, whereas in the presence of 4,4′-bpy the 1D coordination polymer [Zn(acac)₂(4,4′-bpy)]_n (4) was isolated. The molecular structures of 1·dmf and 2·3.7dmf reveal that the [Zn₅] clusters consist of four Zn^II ions which span the corners of a tetrahedron and the fifth resides at its centre. The molecular structure of 3·6dmf reveals that the [Zn₉] clusters consist of two corner sharing tetrahedra and the structure can be described as the addition of two [Zn₅] clusters of 1·dmf and/or 2·3.7dmf followed by the simultaneous abstraction of [Zn(acac)₂] and dmf molecules; this alternative was accomplished by recrystallization of 1·dmf from dmf which yielded 3·6dmf. Each of the μ₃-κN:κN′:κN′′ benzotriazolate ligands in 1·dmf, 2·3.7dmf and 3·6dmf spans an edge of the tetrahedron. The molecular structure of 4 reveals mononuclear [Zn(acac)₂] units bridged via 4,4′-bpy molecules to 1D coordination polymer. Characteristic IR bands of the four complexes are discussed in terms of the coordination modes of the ligands and known structures.     

Synthesis, X-ray structure and anti-corrosion activity of two silver(I) pyrazino complexes

Two new silver(I) pyrazine complexes [Ag₂(ampyz)(NO₃)₂]_n, 1 and {[Ag(2,3-pyzdic)](NO₃)}_n, 2 (where ampyz = aminopyrazine, and 2,3-pyzdic = 2,3-pyrazinedicarboxamide) were synthesized and structurally characterized by X-ray single crystal structure analysis. Complex 1 has a 2D sheet structure through both bridging μ_O,O′-(NO₃) groups and μ_N,N′-pyrazine moieties. A 3D structure with a characteristic (10,3)-d or 10³-utp net is formed through extensive hydrogen bonding. Complex 2 has a 1D chain structure through bridging μ_N,N′-pyrazine moieties. Strong hydrogen bonds further connect these chains to extend the dimensionality to a 3D network structure. The complexes were tested as corrosion inhibitors for mild steel in 0.1 M nitric acid medium using potentiodynamic polarization technique. Both complexes are of mixed type corrosion inhibitors with dominant anodic effect. The inhibition efficiencies are 68% and 50% for complexes 1 and 2, respectively. The inhibition mechanisms of both inhibitors are mainly due to adsorption of the inhibitor molecules on the surface of mild steel. All data were compared and fitted to the kinetic-thermodynamic model. The binding constants K are 3263 and 1147 for complexes 1 and 2, respectively.     

Synthesis, crystal structure and properties of cobalt(II) and nickel(II) coordination polymers supported by functionalized dicarboxylate ligands

Four new coordination polymers of cobalt(II) and nickel(II) with functionalized dicarboxylate ligands, namely, [Co^IIL¹(2,2′-bpy)(H₂O)] (1), [Ni^IIL¹(2,2′-bpy)(H₂O)]·H₂O (2), [Co^II₂(L²)₂(2,2′-bpy)₂(H₂O)] (3) and [Ni^II₂(L²)₂(2,2′-bpy)₂(H₂O)] (4), where H₂L¹ = 2,5-dibenzoylterephthalic acid, H₂L² = 4,6-bis(4-methylbenzoyl)isophthalic acid and 2,2′-bpy = 2,2′-bipyridine, were synthesized and characterized by elemental analysis, IR spectra and thermogravimetric analysis. Complex 1 exhibits a zigzag chain with a C–Hπ interaction between the phenyl ring proton and the phenyl ring of an adjacent chains to form a 2D supramolecular sheet. Complex 2 contains two helical chains which extend into 2D via a C–Hπ interaction between the pyridine ring proton and the pyridine ring. Complexes 3 and 4 are isomorphous with helical chains that extend in the same direction and further link to one another by supramolecular forces into a 2D structure. Moreover, magnetic and luminescence properties have been investigated for 1 and 2, respectively.     

Synthesis and characterization of half-sandwich iridium(III) and rhodium(III) complexes bearing organochalcogen ligands

Reactions of [Cp*M(μ-Cl)Cl]₂ (M = Ir, Rh; Cp* = η⁵-pentamethylcyclopentadienyl) with bi- or tri-dentate organochalcogen ligands Mbit (L1), Mbpit (L2), Mbbit (L3) and [Tm^Me]⁻ (L4) (Mbit = 1,1′-methylenebis(3-methyl-imidazole-2-thione); Mbpit = 1,1′-methylene bis (3-iso-propyl-imidazole-2-thione), Mbbit = 1,1′-methylene bis (3-tert-butyl-imidazole-2-thione)) and [Tm^Me]⁻ (Tm^Me = tris (2-mercapto-1-methylimidazolyl) borate) result in the formation of the 18-electron half-sandwich complexes [Cp*M(Mbit)Cl]Cl (M = Ir, 1a; M = Rh, 1b), [Cp*M(Mbpit)Cl]Cl (M = Ir, 2a; M = Rh, 2b), [Cp*M(Mbbit)Cl]Cl (M = Ir, 3a; M = Rh, 3b) and [Cp*M(Tm^Me)]Cl (M = Ir, 4a; M = Rh, 4b), respectively. All complexes have been characterized by elemental analysis, NMR and IR spectra. The molecular structures of 1a, 2b and 4a have been determined by X-ray crystallography.     

An unprecedented Cu–Schiff base complex existing as two different trinuclear units with strong antiferromagnetic couplings

A new tetradentate N₂O₂ donor Schiff base ligand [OHC₆H₄CHNCH₂CH₂CH(CH₂CH₃)NCHC₆H₄OH = H₂L ] was obtained by 1:2 condensation of 1,3-diaminopentane with salicylaldehyde and has been used to synthesise an unusual copper(II) complex whose asymmetric unit presents two structurally different almost linear trinuclear units [Cu₃(μ-L)₂(ClO₄)₂] [Cu₃(μ-L)₂(H₂O)(ClO₄)₂] (1). The ligand and the complex were characterised by elemental analysis, FT-IR, ¹H NMR and UV–Vis spectroscopy in addition electrochemical and single crystal X-ray diffraction studies were performed for the complex. The magnetic properties of 1 reveal the presence of strong intra-trimer (J₁ = −202(3) cm⁻¹ and J₂ = −233(3) cm⁻¹) as well as very weak inter-trimer (zJ′ = −0.11(1) cm⁻¹) antiferromagnetic interactions.     

Synthesis,structures and magnetic properties of two hexanuclear complexes

The reaction of salicylaldoxime (H₂salox) with Mn(ClO₄)₂ · 6H₂O, NaN(CN)₂ and NEt₃ in MeOH affords a Mn^III₆ hexanuclear complex of [Mn₆O₂(salox)₆(MeOH)₆(NCNCONH₂)₂] (1), while reaction of H₂salox with MnCl₂ · 4H₂O and NEt₄OH in EtOH affords a Mn^III₆ hexanuclear complex of [Mn₆O₂(salox)₆(EtOH)₄(H₂O)₂Cl₂] (2). Both complexes 1 and 2 contain a [Mn^III₆(μ₃-O)₂]¹⁴⁺ core, which is a known structural type in the family of Mn₆ complexes. Variable temperature magnetic susceptibilities and magnetization measurement of complexes 1 and 2 have been carried out. Exchange interactions of metal centers for complexes 1 and 2 are fitted by a full diagonalization matrix method. The fitting results indicate that both complexes 1 and 2 have the ground-state spin value of S = 4, and the ground state of complex 1 has the much closer energy to low-lying spin states than that of complex 2. Magnetization measurements at 2.0–4.0 K and 10–70 kG confirm that the ground state is S = 4, with significant magnetoanisotropy as gauged by the D value of ?0.82 cm^?1 and ?1.18 cm^?1, for 1 and 2, respectively. The frequency dependence of the out-of-phase component in alternating current magnetic susceptibilities for both complexes 1 and 2 indicates the slow magnetic relaxation of superparamagnetic behaviour with a U_eff of 27.0(1) K and τ₀ = 3.8(2) × 10^?9 s for complex 1, and U_eff of 25.1(6) K and τ₀ = 4.6(1) × 10^?8 s for complex 2.     

A novel 18-metallacrown-6 complex: Synthesis, structural characterization and magnetic properties

The novel 18-metallacrown-6 complex, with the formula of [Mn₆(C₁₁H₁₁N₂O₃)₆(CH₃CH₂OH)₆]·3C₃H₇NO·2CH₃CH₂OH (1) (pmshz = N-propanoyl-3-methyl-salicylhydrazide), has been prepared and characterized. The self-assembled, manganese complex assumes a nearly planar cyclic structure with an [Mn–N–N]₆ backbone. Due to the coordination, the ligand enforces the stereochemistry of the Mn³⁺ ions as a propeller shape with alternating …ΔΛΔΛ… configurations. The magnetic properties of the metallacrown molecule are characterized by a weak antiferromagnetic exchange interaction between the Mn³⁺ ion spins with S = 2 in the cyclic system.     

Coordination chemistry of di-2-pyridylketone. Synthesis, spectroscopic investigations, X-ray studies and DFT calculations of Re(III) and Re(V) complexes

The paper presents a combined experimental and computational study of Re(III) and Re(V) complexes containing di-2-pyridylketone and its gem-diol form – [ReCl₃(dpk-N,O)(PPh₃)] (1), [ReCl₃(dpk-N,N′)(OPPh₃)] (2) and [ReOBr₃(dpk-OH)]·2(dpkH⁺Br⁻) (3). All the complexes have been characterized spectroscopically and structurally (by single-crystal X-ray diffraction). The complex 2 has been additionally studied by magnetic measurement. The magnetic behavior of 2 is characteristic of mononuclear octahedral Re(III) complex with d⁴ low-spin (³T_1g ground state) and arise because of the large spin–orbit coupling (ζ = 2500 cm⁻¹), which gives diamagnetic ground state. DFT and time-dependent (TD)DFT calculations have been carried out for [ReCl₃(dpk-N,N′)(OPPh₃)] and [ReOBr₃(dpk-OH), and their UV–vis spectra have been discussed on this basis.     

Synthesis and structure of mixed-metal thiolate complex Cp′Cr(CO)2(μ-SBu)Pt(PPh3)2: Side-on-coordination of Cr–S double bond with platinum

The reaction of [Cp′Cr(CO)₂(μ-SBu)]₂ (1) (Cp′ = MeC₅H₄) with (PPh₃)₂Pt(PhCCPh) gives Cp′Cr(CO)₂(μ-SBu)Pt(PPh₃)₂ (2) which could be regarded as a product of the substitution of acetylene ligand at platinum by a monomeric chromium–thiolate fragment. According to the X-ray diffraction analysis 2 contains single Cr–Pt (2.7538(15)) and Pt–S (2.294(2) Å) bonds while Cr–S bond (2.274(3) Å) is shortened in comparison with ordinary Cr–S bonds (2.4107(4)–2.4311(4) Å) in 1. The bonding between Cr–S fragment and platinum atom is similar to the olefine coordination in their platinum complexes.     

Theoretical studies on the structural and optical properties of a series of Os(II) diimine complexes [Os(NN)(CO)2I2] (NN = 2,2′-bipyridine(bpy), 4,4′-di-tert-butyl-2,2′-bipyridine(dbubpy), 4,4′-dichlorine-2,2′-bipyridine(dclbpy))

The ground- and excited-state structures for a series of Os(II) diimine complexes [Os(NN)(CO)₂I₂] (NN = 2,2′-bipyridine (bpy) (1), 4,4′-di-tert-butyl-2,2′-bipyridine (dbubpy) (2), and 4,4′-dichlorine-2,2′-bipyridine (dclbpy) (3)) were optimized by the MP2 and CIS methods, respectively. The spectroscopic properties in dichloromethane solution were predicted at the time-dependent density functional theory (TD-DFT, B3LYP) level associated with the PCM solvent effect model. It was shown that the lowest-energy absorptions at 488, 469 and 539 nm for 1–3, respectively, were attributed to the admixture of the [d_xy (Os) → π^*(bpy)] (metal-to-ligand charge transfer, MLCT) and [p(I) → π^*(bpy)] (interligand charge transfer, LLCT) transitions; their lowest-energy phosphorescent emissions at 610, 537 and 687 nm also have the ³MLCT/³LLCT transition characters. These results agree well with the experimental reports. The present investigation revealed that the variation of the substituents from H → t-Bu → Cl on the bipyridine ligand changes the emission energies by altering the energy level of HOMO and LUMO but does not change the transition natures.     

Co(III) complexes of Me-salpn and Me-salbn and the ring size effect on the coordination modes and electrochemical properties: The crystal structures of trans-[Co(Me-salpn)(py)2]PF6 and cis-α-[Co(Me-salbn)(4-Mepy)2]BPh4 · 4-Mepy

The synthesis and characterization of a series of cobalt(III) complexes of the general type [Co(N₂O₂)(L₂)]⁺ are described. The N₂O₂ Schiff base ligands used are Me-salpn (H₂Me-salpn = N,N′-bis(methylsalicylidene)-1,3-propylenediamine) (1–3) and Me-salbn (H₂Me-salbn = N,N′-bis(methylsalicylidene)-1,4-butylenediamine) (4–5). The two ancillary ligands L include: pyridine (py) 1, 3-metheylpyridine (3-Mepy) 2, 1-methylimidazole (1-MeIm) 3, 4-methylpyridine (4-Mepy) 4 and pyridine (py) 5. These complexes have been characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structures of trans-[Co^III(Me-salpn)(py)₂]PF₆, 1, and cis-α-[Co^III(Me-salbn)(4-Mepy)₂]BPh₄ · 4-Mepy, 4, have been determined by X-ray diffraction. Examination of the solution and crystalline structures revealed that the outer coordination sphere of the complexes exerts a noticeable influence on the inner coordination sphere of the Co(III) ion. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial (R-py)–cobalt bonds. It has also been observed that the Co(III) state is stabilized with increasing the flexibility of the ligand environment.     

Hydroformylation of oct-1-ene catalyzed by dinuclear gem-dithiolato-bridged rhodium(I) complexes and phosphorus donor ligands

The dinuclear gem-dithiolato bridged compounds [Rh₂(μ-S₂Cptn)(cod)₂] (1) (CptnS₂²⁻ = 1,1-cyclopentanedithiolato), [Rh₂(μ-S₂Chxn)(cod)₂] (2) (ChxnS₂²⁻ = 1,1-cyclohexanedithiolato), [Rh₂(μ-S₂CBn₂)(cod)₂] (3) (Bn₂CS₂²⁻ = 1,3-diphenyl-2,2-dithiolatopropane) and [Rh₂(μ-S₂CⁱPr₂)(cod)₂] (4) (ⁱPr₂CS₂²⁻ = 2,4-dimethyl-2,2-dithiolatopentane) dissolved in toluene in the presence of monodentate phosphine or phosphite P-donor ligands under carbon monoxide/hydrogen (1:1) atmosphere are efficient catalysts for the hydroformylation of oct-1-ene under mild conditions (6.8 atm of CO/H₂ and 80 °C). The influence of the gem-dithiolato ligand, the P-donor co-catalyst and the P/Rh ratio on the catalytic activity and selectivity has been explored. Aldehyde selectivities higher than 95% and turnover frequencies up to 245 h⁻¹ have been obtained using P(OMe)₃ as modifying ligand. Similar activity figures have been obtained using P(OPh)₃ although the selectivities are lower. Regioselectivities toward linear aldehyde are in the range 75–85%. The performance of the catalytic systems [Rh₂(μ-S₂CR₂)(CO)₂(PPh₃)₂]/PPh₃ has been found to be comparable to the systems [Rh₂(μ-S₂CR₂)(cod)₂] at the same P/Rh ratio. The system [Rh₂(μ-S₂CBn₂)(cod)₂] (3)/P(OPh)₃ has been tested in the hydroformylation-isomerization of trans-oct-2-ene. Under optimized conditions up to 54% nonanal was obtained. Spectroscopic studies under pressure (HPNMR and HPIR) evidenced the formation of hydrido mononuclear species under catalytic conditions that are most probably responsible for the observed catalytic activity.     

Nitric oxide and singlet oxygen photo-generation by light irradiation in the phototherapeutic window of a nitrosyl ruthenium conjugated with a phthalocyanine rare earth complex

The photochemical, photophysical and photobiological studies of a mixture containing cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] (H₂-dcbpy = 4,4′-dicarboxy-2,2′-bipyridine) and Na₄[Tb(TsPc)(acac)] (TsPc = tetrasulfonated phthalocyanines; acac = acetylacetone), a system capable of improving photodynamic therapy (PDT), were accomplished. cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] was obtained from cis-[Ru(H₂-dcbpy)₂Cl₂]·2H₂O, whereas Na₄[Tb(TsPc)(acac)] was obtained by reacting phthalocyanine with terbium acetylacetonate. The UV–Vis spectrum of cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] displays a band in the region of 305 nm (λ_max in 0.1 mol L⁻¹ HCl)(π–π*) and a shoulder at 323 nm (MLCT), while the UV–Vis spectrum of Na₄[Tb(TsPc)(acac)] presents the typical phthalocyanine bands at 342 nm (Soret λ_max in H₂O) and 642, 682 (Q bands). The cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] FTIR spectrum displays a band at 1932 cm⁻¹ (Ru–NO⁺). The cyclic voltammogram of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] complex in aqueous solution presented peaks at E = 0.10 V (NO^+/0) and E = −0.50 V (NO^0/−) versus Ag/AgCl. The NO concentration and ¹O₂ quantum yield for light irradiation in the λ > 550 nm region were measured as [NO] = 1.21 ± 0.14 μmol L⁻¹ and ø_OS = 0.41, respectively. The amount of released NO seems to be dependent on oxygen concentration, once the NO concentration measured in aerated condition was 1.51 ± 0.11 μmol L⁻¹ The photochemical pathway of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)]/Na₄[Tb(TsPc)(acac)] mixture could be attributed to a photoinduced electron transfer process. The cytotoxic assays of cis-[Ru(H-dcbpy^-)₂(Cl)(NO)] and of the mixture carried out with B16F10 cells show a decrease in cell viability to 80% in the dark and to 20% under light irradiation. Our results document that the simultaneous production of NO and ¹O₂ could improve PDT and be useful in cancer treatment.     

Synthesis, EPR spectrum and X-ray structure of tetra-n-butylammonium bis(benzene-1,2-dithiolato(2−)-κS,S′)platinate(III)

The new salt, tetra-n-butylammonium bis(benzene-1,2-dithiolato(2−)-κ²S,S′)platinate(III), [NBu₄][Pt(C₆H₄S₂)₂] (1), has been synthesized in ethanol/water, and fully characterized by single crystal X-ray structure determination. The central platinum in the complex ion [Pt(bdt)₂]⁻ is tetracoordinated by the S atoms of the bdt²⁻ ligands (bdt²⁻ is benzene-1,2-dithiolate) in a square-planar geometry. The well-resolved frozen solution EPR spectrum exhibits rhombic symmetry. The room temperature effective magnetic moment (μ_eff = 1.80 Bohr magneton) is in line with this spectrum and strongly supports the Pt(III) oxidation state in 1. This observation is in excellent agreement with previous results reported on closely related Ni(III), Pd(III) and Pt(III) species.     

Polymerisations of -caprolactone and β-butyrolactone with Zn-, Al- and Mg-based organometallic complexes

The reaction of EtAlCl₂ with 1,2-{LiN(PMes₂)}₂C₆H₄ (Mes = 2,4,6-Me₃C₆H₂) and of butyloctylmagnesium with 1,2-{NH(PPh₂)}₂C₆H₄ gave [AlEt(1,2-{N(PMes₂)}₂C₆H₄-κ²N,N′)(THF)] (1) and [Mg(1,2-{N(PPh₂)}₂C₆H₄-κ²N,N′)(THF)₂] (2), respectively. Complexes 1 and 2 were fully characterised by NMR (¹H, ¹³C, ³¹P) and IR spectroscopy and mass spectrometry. Complexes 1 and 2 were employed as catalysts in the polymerisation of -caprolactone, which produced polymers with a narrow molecular weight distribution. For comparison the polymerisations of -caprolactone and β-butyrolactone were carried out with the Zn complex [ZnPr{1-N(PMes₂)-2-N(PHMes₂)C₆H₄-κ²N,N′}] (3) as catalyst, which produced polymers with narrow molecular weight distributions and high molecular weights.     

Platinum(IV) complexes with α,ω-bis(pyrazol-1-yl) alkanediyl and diethyl ether/thioether ligands. Crystal structures of dibromodimethyl[1,2-bis(pyrazol-1-yl)ethane]platinum(IV) and trimethyl-bis[2-(pyrazol-1-yl)ethyl]etherplatinum(IV) tetrafluoroborate

Reactions of the flexible α,ω-bis(pyrazol-1-yl) compounds 1,2-bis(pyrazol-1-yl)ethane (L1), 1,8-bis(pyrazol-1-yl)-n-octane (L2), bis[2-(pyrazol-1-yl)ethyl]ether (L3) and bis[2-(pyrazol-1-yl)ethyl]thioether (L4) with precursor organometallic platinum complexes ([(PtBr₂Me₂)_n], [(PtIMe₃)₄] and [(PtMe₂(cod)]/I₂) are described herein. The spectroscopic characterization of the platinum(IV) products of these reactions [PtBr₂Me₂{pz(CH₂)_mpz}], m = 2 (1) or 8 (2), [PtI₂Me₂{pz(CH₂)₂pz}] (3), [PtMe₃(pzCH₂CH₂OCH₂CH₂pz)][BF₄] (4) and [PtMe₃(pzCH₂CH₂SCH₂CH₂pz)][CF₃SO₃] (5), where ‘pz’ is pyrazol-1-yl, is discussed. Furthermore, solid state structures of 1, a complex with a seven-membered chelate ring, and 4, a complex bearing the neutral κ²N,N′,κO ligand bis[2-(pyrazol-1-yl)ethyl]ether (L3) are reported.     

Preparation of new dinuclear half-titanocene complexes with ortho- and meta-xylene linkages and investigation of styrene polymerization

Half-titanocene is well-known as an excellent catalyst for the preparation of SPS (syndiotactic polystyrene) when activated with methylaluminoxane (MAO). Dinuclear half-sandwich complexes of titanium bearing a xylene bridge, (TiCl₂L)₂{(μ-η⁵, η⁵-C₅H₄-ortho-(CH₂–C₆H₄–CH₂)C₅H₄}, (4 (L = Cl), 7 (L = O-2,6-iPr₂C₆H₃)) and (TiCl₂L)₂{(μ-η⁵, η⁵-C₅H₄-meta-(CH₂–C₆H₄–CH₂)C₅H₄} (5 (L = Cl), 8(L = O-2,6-iPr₂C₆H₃)), have been successfully synthesized and introduced for styrene polymerization. The catalysts were characterized by ¹H- and ¹³C NMR, and elemental analysis. These catalysts were found to be effective in forming SPS in combination with MAO. The activities of the catalysts with rigid ortho- and meta-xylene bridges were higher than those of catalysts with flexible pentamethylene bridges. The catalytic activity of four dinuclear half-titanocenes increased in the order of 4 < 5 < 7 < 8. This result displays that the meta-xylene bridged catalyst is more active than the ortho-xylene bridged and that the aryloxo group at the titanium center is more effective at promoting catalyst activity compared to the chloride group at the titanium center. Temperature and ratio of [Al]:[Ti] had significant effects on catalytic activity. Polymerizations were conducted at three different temperatures (25, 40, and 70 °C) with variation in the [Al]:[Ti] ratio from 2000 to 4000. It was observed that activity of the catalysts increased with increasing temperature, as well as higher [Al]:[Ti]. Different xylene linkage patterns (ortho and meta) were recognized to be a principal factor leading to the characteristics of the dinuclear catalyst due to its different spatial arrangement, causing dissimilar intramolecular interactions between the two active sites.     

Hexanuclear manganese(III) single-molecule magnets from derivatized salicylamidoximes

Four novel hexanuclear manganese(III) complexes based on derivatized salicylamidoximes, [Mn^III₆(μ₃-O)₂(O₂CPh)₂(Me₂N-sao)₆(EtOH)₄] (1), [Mn^III₆(μ₃-O)₂(O₂CPh)₂(Me₂N-sao)₆(ⁱPrOH)₄] (2), [Mn^III₆(μ₃-O)₂(O₂CPh)₂(Et₂N-sao)₆(EtOH)₄] (3) and [Mn^III₆(μ₃-O)₂(O₂CPh)₂(Et₂N-sao)₆(ⁱPrOH)₄] (4) (Me₂N-Hsao = dimethylsalicylamidoxime; Et₂N-Hsao = diethylsalicylamidoxime), have been prepared and characterized. Single-crystal X-ray diffraction allows one to determine that 1·2CHCl₃ and 4 crystallize in the triclinic system with space group P(–1), whereas 3 crystallizes in the monoclinic system with space group P2₁/n. dc and ac magnetic susceptibility measurements of 1-4 reveal ferromagnetic coupling between Mn(III) metal ions and single-molecule magnet behaviour. The anisotropy barriers are 56, 52, 71 and 59 K for 1, 2, 3 and 4, respectively.