Synthesis, structure and characterization of binuclear copper(Ⅱ) complexes

At room temperature, dibenzoyl peroxide undergoes oxidative addition reaction with metallic copper powder and pyridine N-oxide (triphenylphosphine oxide or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolin) which affords the last products as binuclear copper(II) complexes, [Cu(C5H5NO)-(C6H5COO)2]2(1), [Cu(OPPh3)(C6H5COO)2]2(2) and [Cu(C6H5COO)(C26H2oN2)](3, C26H2oN2 is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolin). The structure of the complexes were characterized by elemental analyses, IR spectra, TG-DTA and magnetic property. Crystals(1) are triclinic, space group P1,a=0.92617(36),b=1.06973(17), c=1.08813(29) nm, a=59.60(2)°, β=74.83(3)°,γ=72.80(2)°, V=0.880 nm3, Dc=1.520 g/cm3, Z=1, R=0.044, Rw=0.048, Mr=805.78, 3477 reflections with I > 3σ(I). Each copper(Ⅱ) ion is coordinated by two bridging bidentate benzoate ligands and one pyridine N-oxide or triphenylphosphine oxide to form dimeric binuclear molecules. The structure of the compound(1) shows a clear centre of symmetry.     

Synthesis and characterization of dinuclear p-, m- and o-xylyl bridged complexes of molybdenum and tungsten. The crystal structures of μ-p-xylyl- bis(η-pentamethyl-cyclopentadienyltri- carbonylmolybdenum) and μ-m-xylyl-bis(η- pentamethylcyclopentadienyltricarbonyltungsten)

The reactions of (M = Mo, W) with α,α′-p-, m- and o-dichloro-xylenes yielded p-, m- and o-xylyl bridged dinuclear complexes of in high yields. All of such new complexes are stable to air and water, even stable in dilute acids and bases.     

Synthesis and characterization of binuclear μ-oxo and μ-telluro molybdenum(V) complexes, [CpMo(O)(μ-Te)]2

Pyrolysis of an in-situ generated intermediate, produced in the reaction of [Cp^∗MoCl₄], 1, (Cp^∗ = η⁵-C₅Me₅) with [LiBH₄·THF], with an excess of difuryl ditelluride in toluene at 90 °C yielded syn and anti isomers of [Cp^∗Mo(O)(μ-Te)]₂ (2, 3) and [Cp^∗₂Mo₂O₂(μ-O)(μ-Te)] (4, 5). In a similar fashion, dibenzyl diselenide yielded syn and anti isomers of [Cp^∗Mo(O)(μ-Se)]₂ (6, 7), along with the known nido-[(Cp^∗Mo)₂B₄H₈Se₂]. Note that in parallel with 2-7, [(Cp^∗Mo)₂B₅H₉] was isolated as the major product in both cases. Compounds 2-7 have been isolated in modest yield as orange to brown crystalline solids. All the new compounds have been characterized in solution by mass, IR, ¹H, ¹³C, ⁷⁷Se and ¹²⁵Te NMR spectroscopy, and the structural types were unequivocally established by crystallographic analysis of 2-4 and 7.     

Synthesis, structures, and catalytic properties for ethylene polymerization of bridged [η,η-C5H4CHPhArO]TiCl2 complexes

A number of bridged half-sandwich titanium complexes [η⁵:η¹-2-C₅H₄CHPh-4-R¹-6-R²C₆H₂O]TiCl₂ [R¹ = H (5), Me (6), ^tBu (7, 8); R² = H (6, 7), ^tBu (5, 8)] were synthesized from the reaction of their corresponding trimethylsilyl substituted ligand precursors 2-Me₃SiC₅H₄CHPh-4-R¹-6-R²C₆H₂OSiMe₃ [R¹ = H (1), Me (2), ^tBu (3, 4); R² = H (2, 3), ^tBu (1, 4)] with TiCl₄ in hexane. All new complexes were characterized by ¹H and ¹³C NMR spectroscopy. Molecular structures of complexes 5 and 8 were determined by single crystal X-ray diffraction analysis. Upon activation with AlⁱBu₃/Ph₃CB (C₆F₅)₄, complexes 5-8 exhibit reasonable catalytic activity for ethylene polymerization and copolymerization with 1-hexene, producing polyethylene and poly(ethylene-co-1-hexene) with moderate molecular weights.     

Synthesis, characterization, and structural study of iron-sulfur core {Cp2Fe2(μ-SEt)2} complexes

The known complexes [Cp₂Fe₂(μ-SEt)₂(MeCN)₂](PF₆)₂ (1) and Cp₂Fe₂(μ-SEt)₂(CN)₂ (2) are prepared to investigate their reactivity. The reaction of complex 2 with equimolar amounts of MeOTf yields a monomethylation product [Cp₂Fe₂(μ-SEt)₂(CN)(CNMe)](OTf) (3). Dimethylation of complex 2 by 2 equiv. MeOTf gives a complex [Cp₂Fe₂(μ-SEt)₂(CNMe)₂](OTf)₂ (4). Complex 1 containing two labile MeCN ligands reacts with several bidentate phosphine ligands, such as dppm, dppa, and dppf, to afford complexes [Cp₂Fe₂(μ-SEt)₂(dppm)](PF₆)₂ (5), [Cp₂Fe₂(μ-SEt)₂(dppa)](PF₆)₂ (6), and [Cp₂Fe₂(μ-SEt)₂(dppf)](PF₆)₂ (7), respectively. The spectroscopic, electrochemical, and reactivity studies of iron-sulfur core complexes are performed. The structures of complexes 1-7 were confirmed by X-ray crystallography.     

Synthesis and characterization of two binuclear nickel(II) complexes of thiophenol-based “end-off” compartmental ligands and their application as catalysts for selective oxidation of sulfides

Reaction of the binucleating S-protected ligand precursors 2-(N,N-dimethylthiocarbamato)-5-methylisophthalaldehyde di-2′-hydroxy anil (I) and 2-(N,N-dimethylthiocarbamato)-5-methylisophthalaldehyde di-2′-hydroxy 5′-methyl anil (II) with nickel(II) acetate tetrahydrate in the presence of pyrazole afforded the binuclear nickel(II) complexes [L^INi₂(pz)] (1) and [L^IINi₂(pz)] (2), respectively. The complexes have been characterized by routine physicochemical studies as well as by X-ray single crystal structure analysis. In both complexes, Ni(II) ions are doubly bridged by the thiophenolic sulfur of the pentadentate Schiff base ligand and a pyrazolate group. Efficient protocols for the oxidation of sulfides to sulfoxides with high selectivities, catalyzed by binuclear μ-thiophenolato-μ-pyrazolatonickel(II) in the presence of urea hydrogen peroxide (UHP) were explored. We obtained predominantly the monooxygenated product. The resulting products are obtained in good to excellent yields within a reasonable time.     

Synthesis and characterization of binuclear Zn(II)–cyclen complexes bridged by α,ω-bis(4-methylphenoxy) alkanes

A series of novel α,ω-bis(4-methylphenoxy) alkane functionalized cyclen ligands were synthesized by the nucleophilic substitution reaction of 1,4,7-tris(tert-butyloxycarbonyl)-1,4,7,10-tetraazacyclododecane and α,ω-bis(4-bromomethylphenoxy) alkanes. The corresponding dimeric Zn(II)–cyclen complexes were obtained by reaction of these ligands with Zn(ClO₄)₂·6H₂O. Ligands and complexes were characterized by FT-IR, ¹H NMR, and elemental analysis.     

Lanthanide complexes of the monovacant Dawson polyoxotungstate [α2-As2W17O61] with 1D chain: Synthesis, structures, and photoluminescence properties

Six new lanthanide complexes, (H₃O)[Ln₃(H₂O)₁₇(α₂-As₂W₁₇O₆₁)]·nH₂O ((1) Ln=Ce^III and n≈13; (2) Ln=Pr^III and n≈9; (3) Ln=Nd^III and n≈14; (4) Ln=Sm^III and n≈8; (5) Ln=Eu^III and n≈4; (6) Ln=Gd^III and n≈7), have been isolated by conventional solution method and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. All the complexes are isomorphic and crystallize in the triclinic space group P-1. These complexes are 1D chain-like structures constructed by lanthanide cations and monovacant Dawson-type [α₂-As₂W₁₇O₆₁]¹⁰⁻ polyoxoanions. The striking feature of the structures is that there are three kinds of coordination environments for lanthanide cations, which are responsible for the formation of polymeric structures. Photoluminescence measurements reveal that 4 and 5 exhibit orange and red fluorescent emission at room temperature, respectively.     

Synthesis, characterization and magnetic properties of novel μ-isophthalato oxovanadium(IV) binuclear complexes

Four novel oxovanadium(IV) binuclear complexes have been synthesized, namely [(VO)₂(IPHTA) (L)₂SO₄ (L denotes 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy) and 5-nitro-1,10-phenanthroline (NO₂-phen)), where IPHTA is the isophthalate dianon. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have IPHTA-bridged structures and consist of two vanadium(IV) atoms in a square-pyramidal environment. The complexes [(VO)₂(IPHTA)(Me₂bpy)₂]SO₄ (1) and [(VO)₂(IPHTA)(bpy)₂]SO₄ (2) were characterized by variable temperature magnetic susceptibility (4–300 K) and the data could be well fitted by the least-squares method to a susceptibility equation derived from the spin Hamiltonian operator, . The exchange integral, J, was found to be −26.8 cm⁻¹ for (1) and −31.0 cm⁻¹ for (2). These results are commensurate with antifferomagnetic interactions between two oxovanadium(IV) ions within each molecule. The influence of different terminal ligands on magnetic interactions between the metals of this kind of complexes is also discussed.     

Synthesis,characterization,structures and magnetic property of chiral oxalate-bridged dicopper(Ⅱ) complexes

The oxalato-bridged dicopper(II) complexes [Cu2(μ-ox)(LRR)2(H2O)2(ClO4)2] (1),[Cu2(μ-ox)(LRR)2(CH3COCH3)2(ClO4)2](1a),[Cu2(μ-ox)(LSS)2(H2O)2(ClO4)2] (2) and [Cu2(μ-ox)(LRR)(LSS)2(CH3COCH3)2(ClO4)2] (3) [LRR = (8R,10R)-(-)-[4,5]-pineno2,2′-bipyridine,LSS = (8S,10S)-(+)-[4,5]-pineno-2,2′-bipyridine;ox2= oxalate] were first prepared.A possible mechanism for the formation of the chial dicopper(II) complexes was proposed.Based on elemental analysis,conductance measurement,UV-Vis spectra,CD spectra and X-ray single-crystal diffraction,the oxalato-bridged structures of 1 and 2 were deduced to adopt two Cu(II) ions and the bridged oxalate lying in the nearly same plane.The crystal structures of 1a and 3 reveal that the coordination geometry around each Cu(II) ion is an elongated and distorted octahedron and two axial solvent molecules and two perchlorate ions are anti to each other respectively in both binuclear molecules.The solution CD spectra of 1 and 2 in the visible d-d range show very weak Cotton effects with peaks at 588 and 779 nm,which are approximately of mirror image,suggesting the optical activities may be derived from the vicinal effects of the chiragenic centers at the pinene group of LRR and LSS,respectively.Complex 1 has been characterized by variable-temperature magnetic susceptibility and the data was least-square fitted to the Blenaey-Bowers equation.The exchange integral J was found to be -338.41(4) cm-1,indicating a strong antiferromagnetic interaction between two copper(II) ions.     

Sublimable bis(β-iminoenolate)palladium(II) complexes and their application as catalysts in Suzuki-Miyaura reactions

The Pd(II) complexes strongly chelated by two β-iminoenolate ligands were easily synthesized in only two steps, and purified based on their sublimable and highly stable property. The Pd(II) complexes anchored on a silica surface showed good catalytic activity in Suzuki-Miyaura reactions (up to 99% yield with 0.05?mol% catalyst). They tolerated a wide range of temperature (rt～110?°C) and various solvents, and could be reused multiple times after simple recovering process.     

Synthesis,spectroscopic studies and magnetic properties of binuclear complexes of the first transition series cations bridged by 2,2′-bipyrimidine

Binuclear complexes [M₂Cl₄(-bpym)], where M = VO²⁺, Fe^II, Co^II or Cu^II and bpym = 2,2-bipyrimidine, and [M₂(hfacac)₄(-bpym)] complexes, where hfacac = hexafluoroacetylacetonate and M = Fe^II, Ni^II or Co^II have been synthesized and characterized by chemical analysis, conductance measurements, i.r., electronic and e.p.r spectroscopies and by magnetic susceptibility measurements (in the 4.2–291K range). Co^II and Fe^II are in a high spin state. [(VO)₂Cl₄(-bpym)] is paramagnetic, without significant interactions. [Fe₂Cl₄(-bpym)] shows a singular behaviour explained by an antiferromagnetic intradimer exchange and a ferromagnetic interdimer interaction. All other complexes are antiferromagnetic, with an intramolecular exchange parameter, J, varying from –3.3 cm^–1 for Co^II/math> to –109 cm^–1 for Cu^II.     

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 characterization of fluoro-substituted β-enaminoketonato titanium complexes and their catalytic behavior of regioselective ethylene/cyclopentadiene copolymerization

The ethylene/cyclopentadiene (CPD) copolymerization behavior by using fluoro-substituted bis(β-enaminoketonato) titanium complexes [FC₆H₄NC(CH₃)CHCO(CF₃)]₂TiCl₂ (1a–1c) has been investigated in detail. Upon utilizing MMAO as a cocatalyst, complexes 1a–1c exhibit high catalytic activities, affording the copolymers with high molecular weight and unimodal molecular weight distribution. Compared with non-substituted complex [C₆H₅NC(CH₃)CHCO(CF₃)]₂TiCl₂ (1), complexes 1a–1c can produce the copolymers with CPD incorporation adjusted in a wide range due to the enhancement of electrophilicity of metal center caused by introducing electron-withdrawing groups. Especially complex 1c bearing fluorine at the para-position of N-aryl moiety provides the highest CPD incorporation, which is nearly two times (18.5 mol%) higher than the non-substituted complex 1 (8.9 mol%) under the same conditions. The highest CPD incorporation up to 24.6 mol% can be easily achieved using this complex. ¹H- and ¹³C-NMR spectra demonstrate that these fluoro-substituted complexes possess regioselective nature with exclusive 1,2-insertion fashion, and alternating ethylene-CPD sequence can be detected at high CPD incorporation.     

Effect of counter cationic geometry on stacking structures and magnetic properties of [Ni(mnt)2]− complexes

The crystal structures and magnetic properties of two new ion-pair complexes, [N-NH₂Py][Ni(mnt)₂] (1) and [N-NH₂Ql][Ni(mnt)₂] (2) (N-NH₂Py⁺ = 1-aminopyridinium, N-NH₂Ql⁺ = 1-aminoquinolinium; mnt^2? = maleonitriledithiolate) have been investigated. The differences of the molecular topology and size of the counter cation result in distinct anionic and cationic stacking patterns in the crystals, namely, in the crystal of 1 the anions (A) and cations (C) alternate to stack into a mixed column in the fashion of …AACCAACC…, and the neighboring columns are connected together via intermolecular H-bonding interactions as well as van der Waals forces; while, in the crystal of 2, the anions and cations alternate to form a mixed columnar stack in the manner of …ACAC…, and the adjacent columns are held together via weak van der Waals forces. Investigations of variable-temperature magnetic susceptibility indicated that 1 is a spin gap system but its magnetic behavior does not follow the Bleaney–Bowers spin dimer model; 2 shows a magnetic feature of linear decrease of χ_mT value upon cooling, and this kind of magnetic behavior is probably related to the presence of temperature independent paramagnetism.     

Synthesis of dipyrrolo[2,3-a:1′,2′,3′-fg]acridin-12(1H)-ones

Acylation reactions of 4,6-dimethoxyindoles with glyoxyloyl chlorides were achieved by the use of graphite powder in 1,2-dichloroethane at reflux. The products were monoketones as a result of decarbonylation, rather than the expected 1,2-diketones. Treatment of these monoketones with base led to their cyclisation and elimination of methanol to afford the novel dipyrrolo[2.3-a:1′,2′,3′-fg]acridin-12(1H)-ones.     

Synthesis of dialkyl, diaryl and metallacyclic complexes of Ni and Pd containing pyridine, α-diimines and other nitrogen ligands: Crystal structures of the complexes cis-NiR2py2 (R=benzyl, mesityl)

The alkylation of NiCl₂py₄ or PdCl₂py₂ with organomagnesium or organolithium reagents affords dialkyl complexes cis-MR₂py₂ (R=Me, CH₂SiMe₃, CH₂Ph, CH₂CMe₂Ph, 2,4,6-C₆H₂Me₃). The methyl and trimethylsilyl derivatives undergo ligand exchange reactions with chelating nitrogen ligands (α-diimines or 2-imidoylpyridines), yielding the corresponding dialkyl derivatives in good to excellent yields. A catalytic amount of PMe₃ induces the transformation of the nickel complex Ni(CH₂CMe₂Ph)₂py₂ into the metallacyclic derivative .The latter, and the related palladacycle , also undergo facile ligand exchange reactions.     

Stable silylenes with acyclic, cyclic, and unsaturated cyclic structures: Effects of heteroatoms and cyclopropyl α-substituents at DFT

The effects of alkyl, amino, phosphino, oxy, and thio moieties on the stability, multiplicity and reactivity of α-cyclopropylsilylenes with acyclic, cyclic, and unsaturated cyclic structures are compared and contrasted at B3LYP/AUG-cc-pVTZ//B3LYP/6-31G∗ level. The simultaneous stabilizing effects of heteroatom and cyclopropyl α-substituents on the above silylenes create the following trend of singlet-triplet energy gaps (?E_S-T): amino ≈ oxy > thio > alkyl > phosphino. The ΔE_S-T values for all the above silylenes increase through cyclization, because cyclization stabilizes singlet states of all our α-heteroatom substitued silylenes while destabilizes their corresponding triplet states. The ΔE_S-T values for all the heteroatom substituted cyclic silylenes decrease upon unsaturation, due to the higher stabilization of triplet compared to the singlet state. Interestingly, isodesmic reactions showed the phosphino substituents stabilize the triplet more than the corresponding singlet states, not only in the unsaturated form but also in the acyclic and cyclic structures. This is in contrast to cyclopropyl which stabilizes singlet considerably more than the corresponding triplet states. The reactivity of the above silylenes is discussed in terms of nucleophilicity, and electrophilicity; showing phosphino- and aminocyclopropylsilylenes more nucleophilic than oxy- and thiocyclopropylsilylenes.     

Synthesis and structures of the silyl bridged bis(indenyl) diruthenium complexes and a novel indenyl nonanuclear ruthenium cluster Ru9(μ6-C)(CO)14(μ3-η:η:η-C9H7)2

Thermal treatment of C₉H₇SiMe₂C₉H₇ and C₉H₇Me₂SiOSiMe₂C₉H₇ with Ru₃(CO)₁₂ in refluxing xylene gave the corresponding diruthenium complexes (E)[(η⁵-C₉H₆)Ru(CO)]₂(μ-CO)₂ [E = Me₂Si (1), Me₂SiOSiMe₂ (2)]. A desilylation product [(η⁵-C₉H₇)Ru(CO)]₂(μ-CO)₂ (3) was also obtained in the latter case. Similar treatment of C₉H₇Me₂SiSiMe₂C₉H₇ with Ru₃(CO)₁₂ gave a novel indenyl nonanuclear ruthenium cluster Ru₉(μ₆-C)(CO)₁₄(μ₃-η⁵:η²:η²-C₉H₇)₂ (5) with carbon-centered tricapped trigonal prism geometry, in addition to the diruthenium complex (Me₂SiSiMe₂)[(η⁵-C₉H₆)Ru(CO)]₂(μ-CO)₂ (4) and the desilylation product 3. Complex 4 can undergo a thermal rearrangement to form the product [(Me₂Si)(η⁵-C₉H₆)Ru(CO)₂]₂ (6). The molecular structures of 1, 2, 4, 5, and 6 were determined by X-ray diffraction.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).