Formation of [8,8-η2-{(μ-Cl)2Ru(η6-p-cym)Ph2PCH2PPh2}-nido-8,7-RhSB9H10], a bimetallic derivative of the novel species [8,8-(η2-dppm)-8-(η1-dppm)-nido-8,7-RhSB9H10]

Treatment of [8,8-(η²-dppm)-8-(η¹-dppm)-nido-8,7-RhSB₉H₁₀] (I) with [Ru(η⁶-p-cym)Cl₂]₂ leads to the formation of a new bimetallic complex, [8,8-η²-{(μ-Cl)₂Ru(η⁶-p-cym)Ph₂PCH₂PPh₂}-nido-8,7-RhSB₉H₁₀], (II) containing the group [(μ-Cl)₂Ru(η⁶-p-cym)Ph₂PCH₂PPh₂] that coordinates in a multidentate mode to Rh.     

Study of the cytotoxic activity of alkenyl-substituted ansa-titanocene complexes

The cytotoxic activity on tumour cell lines, human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x and normal immunocompetent cells, was tested for four different ansa-titanocene dichloride derivatives with potentially reactive substituents [Ti{Me(CH₂CH)Si(η⁵-₅Me₄) (η⁵-C₅H₄)}Cl₂] (1), [Ti{Me(H)Si(η⁵-C₅Me₄)₂}Cl₂] (2), [Ti{Me{(CH₂CH)Me₂SiCH₂CH₂}Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (3) and [Ti{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃(CMe₂(CH₂CH₂CHCH₂)))}Cl₂] (4), showing a very promising activity and opening up the possibility of extensive investigation in this field.     

Reactions of [(η6-Me6C6)Ru(Ph2PCHCH2)Cl2] with 1-ethynylcycloalkanols leading to methoxy-alkenyl carbenes via vinylvinylidene and/or allenylidene intermediates

Methoxy-alkenyl carbenes 1 and 2 have been synthesized by treating a dichloro-methane/methanol solution of the [(η⁶-Me₆C₆)Ru(Ph₂PCHCH₂)Cl₂] complex with an excess of 1-ethynyl-1-cyclohexanol and 1-ethynyl-1-cyclopentanol in the presence of NaPF₆. The compounds were characterized by IR and ¹H, ¹³C{¹H}, ³¹P{¹H} NMR spectroscopies and by elemental analyses. The crystal structure of 2 has also been determined by X-ray crystallography.     

Homoleptic complexes [Ru(L-L)3]2+ (L-L=diphosphine,diarsine)

Homoleptic Ru(II)–diphosphine and Ru(II)–diarsine complexes [Ru(L-L)₃](OTf)₂ (L-L=Me₂P(CH₂)_nPMe₂; n=1, dmpm; n=2, dmpe) and 1,2-C₆H₄(AsMe₂)₂ (diars) have been isolated, in which the Ru(II) state is stabilised to an unprecedented degree, and the crystal structure of [Ru(diars)₃]Cl₂ has been determined.     

Migratory insertion reaction in alkenyl ruthenium(II) complexes containing a trifluoroacetate ligand. X-ray structure of the Ru(η2- O2CCF3)(η1-OCCHCHtBu)(CO)(PPh3)2 complex

Reaction of compound Ru(O₂CCF₃)(CHCH^tBu)(CO)(PPh₃)₂ with CO gives the η¹-alkeneacyl complex Ru(O₂CCF₃)(OCCHCH^tBu)(CO)(PPh₃)₂, which is in equilibrium with the dicarbonyl Ru(O₂CCF₃)(CHCH^tBu)(CO)₂(PPh₃)₂ derivative in CH₂Cl₂ solution. The η¹-acyl form involves an η¹-coordination of the O₂CCF₃ ligand, whereas the dicarbonyl form contains the carboxylate ligand η²-coordinated to the metal. The same mixture of carbonylated compounds can be obtained from the reaction of Ru(CHCH^tBu)Cl(CO)₂(PPh₃)₂ with Na[O₂CCF₃] in a CH₂Cl₂/MeOH solution. These reactions reveal the significance of ancillary bidentate ligands for the η-nature of the acyl–metal bond. The molecular structure of the complex Ru(O₂CCF₃)(OCCHCH^tBu)(CO)(PPh₃)₂ was established by X-ray diffraction study of a monocrystal obtained from a CH₂Cl₂/MeOH solution of the mixture of carbonylated compounds.     

Solvent-controlled assemblies,structures, and properties of two Hg(II) coordination polymers with a multidentate N-donor tecton 3,4-bis(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole

Coordination polymers [Hg(L²)Cl₂]_n (1) and {[Hg₂(L²)Cl₄](DMF)}_n (2) have been assembled from Hg(II) chloride and a novel tripyridyltriazole tecton 3,4-bis(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (L²) in different solvent media. Both complexes have been characterized by IR, microanalysis, powder X-ray diffraction, and thermogravimetric analysis. Single crystal X-ray diffraction indicates that the L² ligands take the (η³, μ₂) and (η⁴, μ₃) binding modes in 1 and 2, respectively, which connect the Hg(II) centers to afford linear and ladder-like 1D arrays. Interestingly, complex 1 exhibits strong solid state fluorescent emission at room temperature due to the intraligand transitions, whereas complex 2 is non-fluorescent.     

Bis-boron-capped tris(dioxime) cage complexes with terminal carbonyl groups

Three clathrochelate complexes, [(p-OHCC₆H₄B)₂(chdd)₃Fe^II]·0.5CH₂Cl₂ (1·0.5CH₂Cl₂, H₂chdd = 1,2-cyclohexanedione-1,2-dioxime), [(p-OHCC₆H₄B)₂(hmbd)₃Mn^II₂]}·Et₃NH·0.5CH₃OH·0.5H₂O (2·0.5CH₃OH·0.5H₂O, H₃hmbd = 2-hydroxy-5-methyl-1,3-benzenedicarboxaldehyde-1,3-dioxime), and [(p-OHCC₆H₄B)₂(hmbd)₃Co^II₂]·Et₃NH·H₂O (3·H₂O), were synthesized through template macrobicyclization using metal-oximates as building blocks. These complexes contained reactive apical formyl substituents. Fe^II in mononuclear complex 1 was wrapped in the cavity formed by condensation of H₂chdd with 4-formylphenylboron acid. The organic frameworks of anion unit of binuclear Mn^II complex 2 and that of binuclear Co^II complex 3 were combined by H₃hmbd with 4-formylphenylboronic acid. Spectroscopic, electrochemical characterizations of complexes 1–3 were exploited. DFT calculation of 1 and 2 was also done for better understanding of the electronic property and charge carrier mobility.     

Oxidative addition of halogens to MoRu(CO)6(dppm)2

Halogens oxidatively add to MoRu(CO)₆(μ-dppm)₂ (1) at ambient temperature to yield [(CO)₂Mo(μ-X)(μ-CO)(μ-dppm)₂Ru(CO)₂]⁺[Mo(CO)₄X₃]⁻, where X=Cl (2) or I (3), dppm=Ph₂PCH₂PPh₂, and the μ-CO is semi-bridging. Complexes 2 and 3 have been characterized by elemental analysis, conductivity, and NMR spectroscopy, while the molecular structure of 3 has been determined by X-ray crystallography. Ignoring a weak metal–metal bond interaction, the cation of 3 is most easily described as pseudo-octahedral at Ru(II) and Mo(0) centres; the anion is a monocapped octahedron that has been described previously.     

Deep eutectic solvents (DES) as green reaction media for the redox isomerization of allylic alcohols into carbonyl compounds catalyzed by the ruthenium complex [Ru(η3:η3-C10H16)Cl2(benzimidazole)]

The bis-allyl Ru(IV) complex [Ru(η³:η³-C₁₀H₁₆)Cl₂(benzimidazole)] (1c) is an active catalyst in the redox isomerization of allylic alcohols into saturated carbonyl compounds using, for the first time, Deep eutectic solvents (DES) as reaction media. A series of primary and secondary allylic alcohols could be isomerized into the corresponding carbonyl compounds in the absence of base. Although high activities and selectivities were reached at short reaction times and with low catalyst loadings (0.2 mol% in Ru) for monosubstituted allylic alcohols, for their disubstituted counterparts, high catalyst loading and longer reaction times were always required. It is important to note that the catalytic system: i) is active in a large-scale experiment, and ii) could be recycled up to four consecutive runs.     

In situ synthesis and dielectric properties of copper(II) and nickel(II) chiral Schiff base complexes

Two chiral Schiff base-containing complexes, [Cu(L¹)](ClO₄)₂·H₂O (1, L¹ = (S,S)-N1,N2-bis((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) and [Ni(L²)₂](ClO₄)₂ (2, L² = (S,S)-N1-((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) were synthesized from the reaction mixture of 1H-imidazole-4-carbaldehyde, (S,S)-1,2-diaminocyclohexane and Cu(ClO₄)₂·6H₂O or Ni(ClO₄)₂·6H₂O in methanol. Single-crystal X-ray diffraction analyses reveal that the in situ generated chiral Schiff base ligands L¹ and L² are bisubstituted and monosubstituted, respectively, corresponding to the different metal ions Cu^II and Ni^II. Variable-frequency and -temperature dielectric properties of 1 and 2 have been studied.     

Reactions of benzene based half sandwich ruthenium(II) complex with 2,6-bis((phenylseleno)methyl)pyridine: Preferential substitution of ring resulting in a catalyst of high activity for oxidation of alcohols

[2,6-Bis((phenylseleno)methyl)pyridine] (L) a (Se, N, Se) pincer ligand synthesized by reacting PhSe^? (in situ generated) with 2,6-bis(chloromethyl)pyridine reacts with [{(η⁶-C₆H₆)RuCl(μ-Cl)}₂] (2:1 molar ratio) by preferential substitution of ring resulting in the first Ru-(Se, N, Se) pincer ligand complex, mer-[Ru(CH₃CN)₂Cl(L)][PF₆](1).H₂O. Similar reaction in 4:1 molar ratio results in mer-[Ru(L)₂][ClO₄]₂(2). The ¹H, ¹³C{¹H} and ⁷⁷Se{¹H} NMR spectra of L, 1 and 2 were found characteristic. The single crystal structures of 1 and 2 were studied by X-ray crystallography. The geometry of Ru in both the complexes is distorted octahedral. The Ru–Se distances are in the ranges 2.4412(16)–2.4522(16) and 2.4583(14)–2.4707(15) ? respectively for 1 and 2. The structural solutions from the crystal data in case of 2, due to inferior quality of its crystals, are suitable for supporting bonding mode of L with Ru(II) only. The 1 shows high catalytic activity for oxidation of primary and secondary alcohols (TON up to 9.7 × 10⁴).     

Structural differences of half-sandwich complexes of scandium and yttrium containing bulky substituents

Scandium and yttrium half-sandwich chloride complexes (η⁵-C₅Me₄R)ScCl₂(THF)₂ R = CH₂Ph (3) or SiMe₂CH₂CH₂Ph (5) and (η⁵-C₅Me₄R)YCl₂(THF)₂ R = CH₂Ph (4) or SiMe₂CH₂CH₂Ph (6) were prepared by metathetic reactions of the corresponding substituted lithium or potassium cyclopentadienides with scandium or yttrium trichloride. A mutual comparison of the determined solid state structures of 4 and 5 revealed the tetranuclear character in the case of scandium complex containing C₅Me₄SiMe₂CH₂CH₂Ph ligand, while a formation of the trinuclear ate-complex 4 incorporating lithium was observed for the combination of yttrium and the benzyl substituted tetramethyl cyclopentadienyl. Moreover, the steric effect of addition of another differently substituted cyclopentadienyl ring into the molecule was evaluated.     

Asymmetric transfer hydrogenation of 1-phenyl dihydroisoquinolines using Ru(II) diamine catalysts

A new [Ru(II)(η⁶-p-cymene)(1R,2R)-N-((1S,2S)-borneol-10-sulfonyl)-1,2-diphenylethylenediamine] catalyst for the asymmetric transfer hydrogenation of both 1-alkyl and 1-aryl dihydroisoquinolines has been isolated. For the first time in this type of reaction, the catalyst employs an N-alkylsulfonyl group instead of N-arylsulfonyl.     

Reactions of cyclic and linear alkynols with a phosphinic iron(II) centre

Treatment of a MeOH solution of trans-[FeBr₂(depe)₂] (depe=Et₂PCH₂CH₂PEt₂) with HCCC₆H₁₀OH or HCC(CH₂)_nOH (n=1 or 2), in the presence of NaBPh₄, forms the cyclic allenylidene trans-[FeBr(CCC₆H₁₀)(depe)₂][BPh₄] or the alkyne trans-[FeBr{η²-HCC(CH₂)_nOH}(depe)₂][BPh₄] (n=1 or 2) complexes, respectively.     

Synthesis,characterization and compared reactivity of asymmetrical ansa-metallocenes

Rac and meso ansa-zirconocenes [Zr{1-Me₂Si(3-R-(η⁵-C₉H₅))(3-R′-(η⁵-C₉H₅))}Cl₂] (R = Et, R′ = H; R = Pr, R′ = H; and R = Et, R′ = Pr) 4–9 have been prepared by the reaction of ZrCl₄ with the corresponding dilithiated derivatives from the ligands {1-Me₂Si(3-R-(η⁵-C₉H₅))(3-R′-(η⁵-C₉H₅))} (R = Et, R′ = H 1; R = Pr, R′ = H 2; and R = Et, R′ = Pr 3) in diethyl ether/toluene at ?78 °C. The molecular structure of rac [Zr{1-Me₂Si(3-Et-(η⁵-C₉H₅))(3-Pr-(η⁵-C₉H₅))}Cl₂] 8 has been determined by single crystal X-ray diffraction studies, which show a pseudotetrahedral environment formed by the two chlorine ligands and two η⁵-coordinated indenyl ligands. The activity in homogeneous and heterogeneous polymerization is compared and discussed.     

Synthesis and structural characterization of isomeric monocarbon (η-dicyclopentenyl)-closo-rhodacarboranes stabilized by the agostic bonding interaction

The [7-Me₃N-nido-7-CB₁₀H₁₂] (1), after being treated with two molar equiv. of Proton Sponge, reacts with [(η⁴-C₁₀H₁₂)₂Rh₂(μ-Cl)₂] (2) in benzene–ethanol solution affording two isomeric monocarbon (η-dicyclopentenyl)-closo-rhodacarborane complexes, differing in hapticity of the carbocyclic ligand, viz. [2,2-{(2′,3′-η²):(5′-η¹)-C₁₀H₁₃}-1-(Me₃N)-2,1-closo-RhCB₁₀H₁₀] (3) and [2-{(1′-3′-η³)-C₁₀H₁₃}-1-(Me₃N)-2,1-closo-RhCB₁₀H₁₀] (4). Isomeric compounds 3 and 4 were characterized by analytical, multinuclear NMR spectroscopic data as well as by single-crystal X-ray diffraction study, which revealed the existence of an agostic C–H⋯Rh interaction in both the species.     

Iridium(III) complexes based on 5-nitro-2-(2′,4′-difluorophenyl)pyridyl: Syntheses,structures and photoluminescence properties

A series of cyclometalated Ir(III) complexes [Ir(dFNppy)₂(PPh₃)L] (PPh₃ = triphenylphosphine, L = Cl⁻, 1; NCS⁻, 2; NCO⁻, 3; N₃⁻, 4) in which 5-nitro-2-(2′,4′-difluorophenyl)pyridyl (dFNppy) is used as the main ligand are synthesized and characterized. The crystal structures of 3 and 4 are determined by X-ray diffraction analyses. Photoluminescence spectra of 1–4 in CH₂Cl₂ solutions at room temperature show the maximum emission wavelengths (λ_max) in the range from 586 to 627 nm, corresponding to red-orange luminescence. HOMO–LUMO energy levels of 1–4 are estimated by cyclic voltammetry measurements. Compared with corresponding 2-phenylpyridyl (ppy)-containing Ir(III) complexes having same ancillary ligands, 1–4 have obviously smaller HOMO–LUMO energy gaps (E_g). Simultaneously, 1–4 show relatively bigger E_g compared with 2-phenyl-5-nitropyridyl (5-NO₂-ppy)-containing Ir(III) complexes possessing same ancillary ligands. Methods of E_g adjustment are also discussed.     

Metal–metal interaction through CH2–CN bridge: synthesis and characterization of [CpM(L2)NCCH2Fc]PF6 complexes (Fc=ferrocenyl; L=1/2 dppe,PPh3; M=Fe,Ru)

The new complexes [CpM(L₂)NCCH₂Fc]PF₆ (M=Fe 1, Ru 2; Fc=ferrocenyl), have been prepared from reaction of CpM(L₂)X and the ligand Fc–CH₂CN 3 in methanol and in the presence of NH₄PF₆. The compounds were characterized by elemental analysis as well as spectroscopic methods. Electrochemical as well as near-IR measurements suggest a weak metal–metal interaction for the Fe(II)–Fe(III) complex. Hush parameters for this mixed-valence complex suggest a class II Robin–Day type with a moderate metal–metal interaction similar to that observed in the related pyridine bridged systems (η⁵-C₅H₅)Fe-η⁵-C₅H₄–C₅H₄N–ML_n. The unusual electron transfer through a insulating CH₂ group is the first such example for an asymmetric binuclear system.     

Color change of redox-active organometallic dithienylethene complexes by photochemical and redox processes

Photochromic dithienylethene (DTE) derivatives, DTE-MCpL₂ {M = Fe, Ru; Cp = η⁵-cyclopentadienyl; L₂ = (CO)₂, (CO)PPh₃, dppe (dppe = Ph₂PCH₂CH₂PPh₂)}, with a directly σ-bonded, redox-active organometallic attachment have been prepared and their response to photo- and electrochemical stimuli has been investigated. It turns out that the color of the organometallic derivatives can be controlled not only by photochromic processes but also by one-electron redox processes. The Ru complexes 1^Ru and 2^Ru exhibit reversible photochromism in a manner similar to organic DTE derivatives, with ring closing and ring opening triggered by UV and visible-light irradiation, respectively. Their photochromic behavior is critically dependent on both of the central metal and ligands. One-electron oxidation of the Fe complex 3^Fe gives the corresponding radical cationic species with a visible absorption.     

Coordination modes in zirconium β-diketiminate complexes

Reaction of β-diketiminate lithium salts, nacnac^RLi(THF) (R = 2,6-xylyl (1a), R-CH(Me)Ph (1b)), with ZrCl₄ or ZrCl₄·THF yielded the mono-diketiminate complexes nacnac^RZrCl₃(THF), 2a and 2b. Complex 2a did not react further with a second equivalent of 1a, but with CpLi or IndLi to form pseudo-tetrahedral complexes 3 and 4. No product could be isolated from reaction of 2b with CpLi. Coordination of the diketiminate ligand in 2a is best described as a distorted κ²-, in-plane coordination. Complexes 3 and 4, however, display a haptotropic shift of the diketiminate ligand and its coordination is best described as κ²,η²-coordination. Although not previously described, analyses of available structures in the literature reveal that non-symmetric κ²,η²-coordination is an independent coordination mode, which exists next to the previously described “η⁵-like” coordination.