Novel sandwich complexes of zirconium [C9H5(SiMe3)2](C5Me4R)ZrCl2 (R = CH3, CH2CH2NMe2): Synthesis and reduction behavior

Novel half-sandwich [C₉H₅(SiMe₃)₂]ZrCl₃ (3) and sandwich [C₉H₅(SiMe₃)₂](C₅Me₄R)ZrCl₂ (R = CH₃ (1), CH₂CH₂NMe₂ (2)) complexes were prepared and characterized. The reduction of 2 by Mg in THF lead to (η⁵-C₉H₅(SiMe₃)₂)[η⁵:η²(C,N)-C₅Me₄CH₂CH₂N(Me)CH₂]ZrH (7). The structure of 7 was proved by NMR spectroscopy data. Hydrolysis of 2 resulted in the binuclear complex ([C₅Me₄CH₂CH₂NMe₂]ZrCl₂)₂O (6). The crystal structures of 1 and 6 were established by X-ray diffraction analysis.     

Mono- and bis-(2-dimethylaminoethyl)tetramethylcyclopentadienyl zirconium(IV) complexes: synthesis and structural studies in crystalline state and in solutions

A novel half-sandwich Zr(IV) complex [η⁵:η¹-N-C₅(CH₃)₄CH₂CH₂N(CH₃)₂]ZrCl₃ (6) together with zirconocene dichlorides [η⁵-C₅(CH₃)₄CH₂CH₂N(CH₃)₂][η⁵-C₅(CH₃)₅]ZrCl₂ (4) and [η⁵-C₅(CH₃)₄CH₂CH₂N(CH₃)₂]₂ZrCl₂ (5) have been prepared. Complex 6 has been isolated and characterized in three different forms, namely, as an adduct with THF 6a, an adduct with tetrahydrothiophene 6b, and a solvent-free form 6c. Molecular structures of complexes 4, 6b, and 6c have been established by X-ray diffraction analysis. Complex 6c has been shown to be a monomeric solvent-free half sandwich Zr(IV) complex. The dynamic behavior of complex 6a in a non-solvating medium (an equilibrium between 6a and 6c along with a degenerate interconversion of the Zr-C_cp-CH₂-CH₂-N(CH₃)₂-(Zr) pseudo-five-member metallacycle) have been studied by the variable-temperature ¹H and ¹³C{¹H} NMR spectroscopy. The activation parameters for the degenerate five-member cycle interconversion have been elucidated.     

Complexes of titanium and zirconium based on [C5Me4CH2-(2-C5H4N)] ligand

Half-sandwich [η⁵:η¹-κN-C₅Me₄CH₂-(2-C₅H₄N)]MCl₃ (M = Ti (4), Zr (5)) and sandwich [η⁵-C₅Me₄CH₂-(2-C₅H₄N)][η⁵-C₅Me₅]ZrCl₂ (6) ring-peralkylated complexes have been prepared and characterized. Evidence of the intramolecular coordination of the side-chain pyridyl group both in 4 and 5 in solutions is provided by NMR spectroscopy data. Crystal structure of an adduct 5-py with one molecule of pyridine has been established by X-ray diffraction analysis.     

Sulfur and oxygen functionalized cyclopentadienyl half-sandwich cobalt complexes with 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolato ligands

Sulfur and oxygen functionalized cyclopentandienyl half-sandwich cobalt dicarbonyl complexes [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]Co(CO)₂ (3) and [η⁵-C₅H₄(CH₂)₂OCH₃]Co(CO)₂ (7) were prepared. Oxidation of 3 or 7 with I₂ led to formation of 18-electron complexes [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]CoI₂ (4) and [η⁵-C₅H₄(CH₂)₂OCH₃]Co(CO)I₂ (8). The reactions of diiodide complex (4) with dilithium 1,2-dicarba-closo-dodecaborane(12)-1,2-dichalcogenolates [(THF)₃LiE₂C₂B₁₀H₁₀Li(THF)]₂ [E=S (1a), Se (1b)] afforded 18-electron mononuclear complexes [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]Co(E₂C₂B₁₀H₁₀) [E=S (5a), Se (5b)] in which sulfur atoms of side-chain were attached via an intramolecular coordination. Complex 7 reacted with 1a and 1b to give the binuclear complexes {[η⁵-C₅H₄(CH₂)₂OCH₃]Co(E₂C₂B₁₀H₁₀)}₂ [E=S (10a), Se (10b)]. The molecular structures of 5a and 10b were determined by X-ray crystallographic analysis. According to the X-ray structure analyses, 10b contains two o-carborane diselenolate bridges, and each Cp^′Co fragment is attached to one terminal and two bridging selenolato ligands. The central Co₂Se₂ four-membered ring is planar, and the direct metal-metal interaction is absent.     

Formation of ferraboranes from pentaborane(9) or BH3 · thf and an electron-rich cyclopentadienyl iron phosphine hydride

[(η⁵-C₅R₅)Fe(PMe₃)₂H] (R = H, Me) can be made in good yields in a simple one-pot reaction between FeCl₂, PMe₃, C₅R₅H (R = H, Me) and Na/Hg in thf. Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with pentaborane(9) gives the known metallaborane [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (1) in improved yield as well as the new metallaboranes [(η-C₅H₅)-nido-2-FeB₅H₈{μ-5,6-Fe(η⁵-C₅H₅)(PMe₃)(μ-6,7-H)}] (2), [(η-C₅H₅)(PMe₃)-arachno-2-FeB₃H₈] (3), [(η⁵-C₅H₅)₂-capped-nido-2,3-Fe₂B₄H₈] (4), [(η⁵-C₅H₅)-nido-2-FeB₄H₇(PMe₃)] (5) and [(η⁵-C₅H₅)-nido-2-FeB₅H₈(PMe₃)] (6). Reaction of [(η⁵-C₅Me₅)Fe(PMe₃)₂H] with pentaborane(9) gives predominantly [(η⁵-C₅Me₅)-nido-2-FeB₅H₁₀] (7) and [(η⁵-C₅Me₅)(PMe₃)-arachno-2-FeB₃H₈] (8). Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with 2 equiv. of BH₃ · thf gives low yields of ferrocene and compound 3. Compound 7 thermally isomerises to the apical isomer [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (9) in low yield. Compounds 1 and 7 deprotonate cleanly in the presence of KH at the unique B-H-B bridge to give [(η⁵-C₅H₅)-nido-2-FeB₅H₉⁻][K⁺] (10) and [(η⁵-C₅Me₅)-nido-2-FeB₅H₉⁻][K⁺] (11) respectively, whilst 6 deprotonates more slowly at one of two equivalent B-H-B bridges to give the fluxional anion [(η⁵-C₅H₅)-nido-2-FeB₅H₇(PMe₃)⁻] (12).     

Synthesis and reactivity of η-tetramethylcyclopentadienyl-propenyl rhenium complexes: Molecular structure of [(η:η-C5Me4CH2CHCH2)Re(CO)2]

The fulvene complexes [(η⁶-C₅Me₄CH₂)Re(CO)₂(R)] (1a, RI; 1b, RC₆F₅) react at the exocyclic methylene carbon with a vinylmagnesium bromide solution to produce the anionic species [(η⁵-C₅Me₄CH₂CHCH₂)Re(CO)₂(R)]⁻. Protonation with HCl at 0 °C produces the hydride complexes [trans-(η⁵-C₅Me₄CH₂CHCH₂)Re(CO)₂(R)(H)] (2a, RI; 2b, RC₆F₅). Thermolysis of an hexane solution of the iodo-hydride (2a) under a CO atmosphere yields the complex [(η⁵-C₅Me₄CH₂CHCH₂)Re(CO)₃] (3) and [Re(CO)₅I] as by-product. Thermolysis of 2b produced three new products, mainly the chelated complex [(η⁵:η²-C₅Me₄CH₂CHCH₂)Re(CO)₂] (4) and complex 3, with a non-coordinated olefin group, in moderated yield, and traces of [Re(CO)₅(C₆F₅)]. Thermolysis of an hexane solution of 2 in presence of an excess of PMe₃, afforded the phosphine derivative [(η⁵-C₅Me₄CH₂CHCH₂)Re(CO)₂(PMe₃)] (5). All the complexes were characterized by IR, ¹H, ¹³C and ³¹P NMR spectroscopies and mass spectrometry. The molecular structure of 4 has also been determined. The molecule exhibits a formal three-legged piano-stool structure, with two CO groups, and the third position corresponding to the η²-coordination of the propenyl side arm of the η⁵-C₅Me₄ ring.     

Mono and dinuclear rhodium, iridium and ruthenium complexes containing chelating 2,2′-bipyrimidine ligands: Synthesis, molecular structure, electrochemistry and catalytic properties

The mononuclear cations [(η⁵-C₅Me₅)RhCl(bpym)]⁺ (1), [(η⁵-C₅Me₅)IrCl(bpym)]⁺ (2), [(η⁶-p-PrⁱC₆H₄Me)RuCl(bpym)]⁺ (3) and [(η⁶-C₆Me₆)RuCl(bpym)]⁺ (4) as well as the dinuclear dications [{(η⁵-C₅Me₅)RhCl}₂(bpym)]²⁺ (5), [{(η⁵-C₅Me₅)IrCl}₂(bpym)]²⁺ (6), [{(η⁶-p-PrⁱC₆H₄Me)RuCl}₂(bpym)]²⁺ (7) and [{(η⁶-C₆Me₆)RuCl}₂(bpym)]²⁺ (8) have been synthesised from 2,2′-bipyrimidine (bpym) and the corresponding chloro complexes [(η⁵-C₅Me₅)RhCl₂]₂, [(η⁵-C₅Me₅)IrCl₂]₂, [(η⁶-PrⁱC₆H₄Me)RuCl₂]₂ and [(η⁶-C₆Me₆)RuCl₂]₂, respectively. The X-ray crystal structure analyses of [3][PF₆], [5][PF₆]₂, [6][CF₃SO₃]₂ and [7][PF₆]₂ reveal a typical piano-stool geometry around the metal centres; in the dinuclear complexes the chloro ligands attached to the two metal centres are found to be, with respect to each other, cis oriented for 5 and 6 but trans for 7. The electrochemical behaviour of 1-8 has been studied by voltammetric methods. In addition, the catalytic potential of 1-8 for transfer hydrogenation reactions in aqueous solution has been evaluated: All complexes catalyse the reaction of acetophenone with formic acid to give phenylethanol and carbon dioxide. For both the mononuclear and dinuclear series the best results were obtained (50 °C, pH 4) with rhodium complexes, giving turnover frequencies of 10.5 h⁻¹ for 1 and 19 h⁻¹ for 5.     

Thermolysis of titanocene methyl compounds bearing t-butyl- and benzyltetramethylcyclopentadienyl ligands

Elimination of methane during thermolysis of title compounds results in the formation of σ-Ti-C bond to t-butyl or benzyl group. The t-butyl-containing titanocene methyl compound [Ti(III)Me(η⁵-C₅Me₄t-Bu)₂] (5) eliminates methane at 110 °C to give cleanly [Ti(III)(η⁵:η¹-C₅Me₄CMe₂CH₂)(η⁵-C₅Me₄t-Bu)] (6). The methyl derivative of analogous benzyl-containing titanocene [Ti(III)Me(η⁵-C₅Me₄CH₂Ph)₂] was not isolated because it eliminated methane at ambient temperature to give [Ti(III)(η⁵:η¹-C₅Me₄CH₂-o-C₆H₄)(η⁵-C₅Me₄CH₂Ph)] (7) with one phenyl ring linked to titanium atom in ortho-position. The corresponding titanocene dimethyl compound [TiMe₂{η⁵-C₅Me₄t-Bu)}₂] (9) eliminates two methane molecules at 110 °C to give the singly tucked-in 1,1-dimethylethane-1,2-diyl-tethered titanocene [Ti{η⁵:η¹:η¹-C₅Me₃(CH₂)(CMe₂CH₂)}(η⁵-C₅Me₄t-Bu)] (11). In distinction, the analogous benzyl derivative [TiMe₂(η⁵-C₅Me₄CH₂Ph)₂] (10) eliminates at 110 °C only one methane molecule to afford [TiMe(η⁵:η¹-C₅Me₄CH₂-o-C₆H₄)(η⁵-C₅Me₄CH₂Ph)] (12) containing one phenyl group attached to titanium in o-position and one methyl group persisting on the titanium atom. This compound is stable at 150 °C for at least 3 h. The crystal structures of 5, 6, 7, and 10 were determined.     

Synthesis and structure of dinuclear dimethylene- or 1,4-phenylene-linked bis(decamethyltitanoceneoxide) (Ti) complexes

The singly tucked-in titanocene [Ti(η⁵-C₅Me₅)(η⁵:η¹-C₅Me₄CH₂)] (1) reacts smoothly with ethylene glycol or hydroquinone to give bis(titanoceneoxide) (Ti^III) complexes [CH₂OTi(η⁵-C₅Me₅)₂]₂ (2) and [(η⁵-C₅Me₅)₂TiOC₆H₄OTi(η⁵-C₅Me₅)₂] (3) containing dimethylene and 1,4-phenylene link, respectively. EPR spectra of 2 in 2-methyltetrahydrofuran glass and 3 in toluene glass revealed that the unpaired d¹ electrons are in interaction to form triplet state molecules. The Ti-Ti distance derived from the zero-field splittings D for the two conformations of 2 (7.42 Å and 7.66 Å) are in good agreement with the Ti-Ti distance of 7.2430(7) Å from the X-ray diffraction single-crystal analysis. For 3, however, the Ti-Ti distance derived from D (7.65 Å) is by 1.47 Å shorter than the crystallographic distance of 9.1230(8) Å that indicates an enhancement of the through-space dipole-dipole interaction due to the presence of a conjugated quinonide link.     

Mono and dinuclear iridium, rhodium and ruthenium complexes containing chelating carboxylato pyrazine ligands: Synthesis, molecular structure and electrochemistry

The mononuclear complexes [(η⁵-C₅Me₅)IrCl(L¹)] (1), [(η⁵-C₅Me₅)RhCl(L¹)] (2), [(η⁶-p-PrⁱC₆H₄Me)RuCl(L¹)] (3) and [(η⁶-C₆Me₆)RuCl(L¹)] (4) have been synthesised from pyrazine-2-carboxylic acid (HL¹) and the corresponding complexes [{(η⁵-C₅Me₅)IrCl₂}₂], [{(η⁵-C₅Me₅)RhCl₂}₂], [{(η⁶-p-PrⁱC₆H₄Me)RuCl₂}₂], and [{(η⁶-C₆Me₆)RuCl₂}₂], respectively. The related dinuclear complexes [{(η⁵-C₅Me₅)IrCl}₂(μ-L²)] (5), [{(η⁵-C₅Me₅)RhCl}₂(μ-L²)] (6), [{(η⁶-p-PrⁱC₆H₄Me)RuCl}₂(μ-L²)] (7) and [{(η⁶-C₆Me₆)RuCl}₂(μ-L²)] (8) have been obtained in a similar manner from pyrazine-2,5-dicarboxylic acid (H₂L²). Compounds isomeric to the latter series, [{(η⁵-C₅Me₅)IrCl}₂(μ-L³)] (9), [{(η⁵-C₅Me₅)RhCl}₂(μ-L³)] (10), [{(p-PrⁱC₆H₄Me)RuCl}₂(μ-L³)] (11) and [{(η⁶-C₆Me₆)RuCl}₂(μ-L³)] (12), have been prepared by using pyrazine-2,3-dicarboxylic acid (H₂L³) instead of H₂L². The molecular structures of 2 and 3, determined by X-ray diffraction analysis, show the pyrazine-2-carboxylato moiety to act as an N,O-chelating ligand, while the structure analyses of 5-7, confirm that the pyrazine-2,5-dicarboxylato unit bridges two metal centres. The electrochemical behaviour of selected representatives has been studied by voltammetric techniques.     

Titanium(IV) carboxylate complexes: Synthesis,structural characterization and cytotoxic activity

Four titanium(IV) carboxylate complexes [Ti(η⁵-C₅H₅)₂(O₂CCH₂SMes)₂] (1), [Ti(η⁵-C₅H₄Me)₂(O₂CCH₂SMes)₂] (2), [Ti(η⁵-C₅H₅)(η⁵-C₅H₄SiMe₃)(O₂CCH₂SMes)₂] (3) and [Ti(η⁵-C₅Me₅)(O₂CCH₂SMes)₃] (4; Mes = 2,4,6-Me₃C₆H₂) have been synthesised by the reaction of the corresponding titanium derivatives [Ti(η⁵-C₅H₅)₂Cl₂], [Ti(η⁵-C₅H₄Me)₂Cl₂], [Ti(η⁵-C₅H₅)(η⁵-C₅H₄SiMe₃)Cl₂] and [Ti(η⁵-C₅Me₅)Cl₃] and two (for 1–3) or three (for 4) equivalents of mesitylthioacetic acid. Complexes 1–4 have been characterized by spectroscopic methods and the molecular structure of the complexes 1, 2 and 4 have been determined by X-ray diffraction studies. The cytotoxic activity of 1–4 was tested against tumor cell lines human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x, and normal immunocompetent cells, that is peripheral blood mononuclear cells PBMC and compared with those of the reference complexes [Ti(η⁵-C₅H₅)₂Cl₂] (R1), [Ti(η⁵-C₅H₄Me)₂Cl₂] (R2), [Ti(η⁵-C₅H₅)(η⁵-C₅H₄SiMe₃)Cl₂] (R3) and cisplatin. In all cases, the cytotoxic activity of the carboxylate derivatives was higher than that of their corresponding dichloride analogues, indicating a positive effect of the carboxylato ligand on the final anticancer activity. Complexes 1–4 are more active against K562 (IC₅₀ values from 72.2 to 87.9 μM) than against HeLa (IC₅₀ values from 107.2 to 142.2 μM) and Fem-x cells (IC₅₀ values from 90.2 to 191.4 μM).     

Syntheses and characterization of [(η-C6Me6)Ru(μ-N3)(X)]2 (X = N3 and Cl) complexes and their reactions towards mono- and bidentate ligands

The reaction of the complex [{(η⁶-C₆Me₆)Ru(μ-Cl)Cl}₂] 1 with sodium azide ligand gave two new dimers of the composition [{(η⁶-C₆Me₆)Ru(μ-N₃)(N₃)}₂] 2 and [{(η⁶-C₆Me₆)Ru(μ-N₃)Cl}₂] 3, depending upon the reaction conditions. Complex 3 with excess of sodium azide in ethanol yielded complex 2. These complexes undergo substitution reactions with monodentate ligands to yield monomeric complexes of the type [(η⁶-C₆Me₆)Ru(X)(N₃)(L)] {X = N₃, Cl, L = PPh₃ (4a, 9a); PMe₂Ph (4b, 9b); AsPh₃ (4c, 9c); X = N₃, L = pyrazole (Hpz) (5a); 3-methylpyrazole (3-Hmpz) (5b) and 3,5-dimethyl-pyrazole (3,5-Hdmpz) (5c)}. Complexes 2 and 3 also react with bidentate ligands to give bridging complexes of the type [{(η⁶-C₆Me₆)Ru(N₃)(X)]₂(μ-L)} {X = N₃, Cl, L = 1,2-bis(diphenylphosphino)methane (dppm) (6, 10); 1,2-bis(diphenylphosphino)ethane (dppe) (7, 11); 1,2-bis(diphenylphosphino)propane (dppp) (8, 12); X = Cl, L = 4,4-bipyridine (4,4′-bipy) (13)}. These complexes were characterized by FT-IR and FT-NMR spectroscopy as well as by analytical data.The molecular structures of the representative complexes [{(η⁶-C₆Me₆)Ru(μ-N₃)(N₃)}₂] 2, [{(η⁶-C₆Me₆)Ru(μ-N₃)Cl}₂] 3,[(η⁶-C₆Me₆)Ru(N₃)₂(PPh₃)] 4a and [{(η⁶-C₆Me₆)Ru(N₃)₂}₂ (μ-dppm)] 6 were established by single crystal X-ray diffraction studies.     

Anticancer activity of new organo-ruthenium, rhodium and iridium complexes containing the 2-(pyridine-2-yl)thiazole N,N-chelating ligand

The dinuclear dichloro complexes [(η⁶-arene)₂Ru₂(μ-Cl)₂Cl₂] and [(η⁵-C₅Me₅)₂M₂(μ-Cl)₂Cl₂] react with 2-(pyridine-2-yl)thiazole (pyTz) to afford the cationic complexes [(η⁶-arene)Ru(pyTz)Cl]⁺ (arene = C₆H₆1, p-ⁱPrC₆H₄Me 2 or C₆Me₆3) and [(η⁵-C₅Me₅)M(pyTz)Cl]⁺ (M = Rh 4 or Ir 5), isolated as the chloride salts. The reaction of 2 and 3 with SnCl₂ leads to the dinuclear heterometallic trichlorostannyl derivatives [(η⁶-p-ⁱPrC₆H₄Me)Ru(pyTz)(SnCl₃)]⁺ (6) and [(η⁶-C₆Me₆)Ru(pyTz)(SnCl₃)]⁺ (7), respectively, also isolated as the chloride salts. The molecular structures of 4, 5 and 7 have been established by single-crystal X-ray structure analyses of the corresponding hexafluorophosphate salts. The in vitro anticancer activities of the metal complexes on human ovarian cancer cell lines A2780 and A2780cisR (cisplatin-resistant), as well as their interactions with plasmid DNA and the model protein ubiquitin, have been investigated.     

New alkenyl-substituted group 4 C-ansa-metallocene complexes. Reactivity of the substituent at the carbon ansa bridge

The allyl-substituted group 4 metal complexes [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti, R = CH₂CHCH₂, (2); R = CH₂C(CH₃)CH₂ (3); M = Zr, R = CH₂CHCH₂ (4), R = CH₂C(CH₃)CH₂ (5)] have been synthesized by the reaction of allyl ansa-magnesocene derivatives and the tetrachloride salts of the corresponding transition metal. The dialkyl complexes ] [M = Ti, R = CH₂=CHCH₂, R′ = Me (6), R′ = CH₂Ph (7); R = CH₂C(CH₃)CH₂, R′ = Me (8), R′ = CH₂Ph (9); M = Zr, R = CH₂CHCH₂, R′ = Me (10), R′ = CH₂Ph (11); R = CH₂C(CH₃)CH₂, R′ = Me (12), R′ = CH₂Ph (13)] have been synthesized by the reaction of the corresponding ansa-metallocene dichloride complexes 2-5 and two molar equivalents of the alkyl Grignard reagent. Compounds 2-5 reacted with H₂ under catalytic conditions (Wilkinson’s catalyst or Pd/C) to give the hydrogenation products [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = CH₂CH₂CH₃ (14) or R = CH₂CH(CH₃)₂ (15); M = Zr and R = CH₂CH₂CH₃ (16) or R = CH₂CH(CH₃)₂ (17)]. The reactivity of 2-5 has also been tested in hydroboration and hydrosilylation reactions. The hydroboration reactions of 3, 4 and 5 with 9-borabicyclo[3.3.1]nonane (9-BBN) yielded the complexes [M{(9-BBN)CH₂CH(R)CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (18); M = Zr and R = H (19) or R = CH₃ (20)]. The reaction with the silane reagents HSiMe₂Cl gave the corresponding [M{ClMe₂SiCH₂CHRCH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (21); M = Zr and R = H (22) or R = CH₃ (23)]. The reaction of 22 with t-BuMe₂SiOH produced a new complex [Zr{t-BuMe₂SiOSi(Me₂)CH₂CH₂CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (24) through the formation of Si-O-Si bonds. On the other hand, reactivity studies of some zirconocene complexes were carried out, with the insertion reaction of phenyl isocyanate (PhNCO) into the zirconium-carbon σ-bond of [Zr{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}₂Me₂] (25) giving [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr{Me{κ²-O,N-OC(Me)NPh}] as a mixture of two isomers 26a-b. The reaction of [Zr{(n-Bu)(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}(CH₂Ph)₂] (27) with CO also provided a mixture of two isomers [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr(CH₂Ph){κ²-O,C-COCH₂Ph}] 28a-b. The molecular structures of 4, 11, 16 and 17 have been determined by single-crystal X-ray diffraction studies.     

Preparation and characterization of cobalt-containing P,N-ligands and an unusual palladium complex ion pair: their applications in amination reactions

Several cobalt-containing P,N-ligands, alkyne-bridged dicobalt phosphines [(μ-PPh₂CH₂PPh₂)Co₂(CO)₄(μ,η-Me₂NCH₂CCPR₂)] (4a: R=^tBu; 4b: R=Ph; 4c: R=Cy), were prepared from the reactions of corresponding alkynylphosphines Me₂NCH₂CCPR₂ (2a: R=^tBu; 2b: R=Ph; 2c: R=Cy) with a dppm-bridged dicobalt complex [Co₂(CO)₆(μ-P,P-PPh₂CH₂PPh₂)] 3. A unique palladium complex ion pair [(μ-PPh₂CH₂PPh₂)Co₂(CO)₄(μ,η-Me₂NCH₂CCP (^tBu)₂)Pd(η³-C₃H₅)]⁺[(η³-C₃H₅)PdCl₂]⁻7a was obtained from the reaction of 4a with [(η³-C₃H₅)PdCl]₂. Compounds 4a, 4b, and 4c are authentic cobalt-containing P,N-bidentate ligands and can be used for ligation of palladium from various sources such as Pd(OAc)₂ or [(η³-C₃H₅)PdCl]₂. Satisfactory efficiencies were observed for the amination reactions of aryl bromides with morpholine employing either a 4a-chelated palladium complex formed in situ or pre-formed 7a as the catalytic precursor.     

Ruthenium(II), rhodium(III) and iridium(III) based effective catalysts for hydrogenation under aerobic conditions

The new cationic mononuclear complexes [(η⁶-arene)Ru(Ph-BIAN)Cl]BF₄ [η⁶-arene = benzene (1), p-cymene (2)], [(η⁵-C₅H₅)Ru(Ph-BIAN)PPh₃]BF₄ (3) and [(η⁵-C₅Me₅)M(Ph-BIAN)Cl]BF₄ [M = Rh (4), Ir (5)] incorporating 1,2-bis(phenylimino)acenaphthene (Ph-BIAN) are reported. The complexes have been fully characterized by analytical and spectral (IR, NMR, FAB-MS, electronic and emission) studies. The molecular structure of the representative iridium complex [(η⁵-C₅Me₅)Ir(Ph-BIAN)Cl]BF₄ has been determined crystallographically. Complexes 1–5 effectively catalyze the reduction of terephthaldehyde in the presence of HCOOH/CH₃COONa in water under aerobic conditions and, among these complexes the rhodium complex [(η⁵-C₅Me₅)Rh(Ph-BIAN)Cl]BF₄ (4) displays the most effective catalytic activity.     

Reduction-induced o-C–H bond activation of pyridine with decamethylzirconocene dichloride

Treatment of decamethylzirconocene dichloride (η⁵-Cp^∗)₂ZrCl₂ with amalgamated magnesium in pyridine results in formation of the o-C–H bond activation product [η⁵-C₅Me₅]₂ZrH[η²-κC,N-C₅H₄N] (1). X-ray diffraction analysis (solid state) and NMR spectroscopy data (solutions) reveal the lateral positioning of the nitrogen atom in 1. At elevated temperatures, complex 1 smoothly rearranges into its isomer 2 with medial positioning of the N-atom. The parameters of equilibrium between 1 and 2 were measured at different temperatures. A reaction of 1 or a mixture of 1 and 2 (ca. 1:10) with CDCl₃ smoothly and under mild conditions leads to one and the same η²-pyridyl chloride complex [η⁵-C₅Me₅]₂ZrCl[η²-κC,N-C₅H₄N] (3) with medial positioning of the N-atom. The thermodynamic and mechanistic concepts of the paper are discussed with application of the DFT computational data.     

Synthesis and properties of Zr-Co heterodinuclear complexes with a bridging bis(cyclopentadienyl) ligand

[(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(C₅H₅)] reacted with Co₂(CO)₈ to produce a heterodinuclear Zr(IV)-Co(I) complex [(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(η⁵-C₅H₄)Co(CO)₂] (3). Complex 3 underwent oxidative addition of I₂ to give [(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(η⁵-C₅H₄)CoI₂(CO)] (4) having Zr(IV) and Co(III) centers. The carbonyl ligand of 4 was easily replaced with P(OMe)₃ and PPh₃ to afford [(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(η⁵-C₅H₄)CoI₂(L)] (5: L = P(OMe)₃, 6: L = PPh₃). Structures of 5 and 6 were determined by X-ray crystallography. These Zr-Co heterodinuclear complexes catalyzed polymerization of ethylene and propylene.     

Reactivity studies of (η-arene)ruthenium dimeric complexes towards pyrazoles: isolation of amidines, bis pyrazoles and chloro bridged pyrazole complexes

The complex [(η⁶-p-cymene)Ru(μ-Cl)Cl]₂1 reacts with pyrazole ligands (3a-g) in acetonitrile to afford the amidine derivatives of the type [(η⁶-p-cymene)Ru(L)(3,5-HRR′pz)](BF4)₂ (4a-f), where L = {HNC(Me)3,5-RR′pz}; R, R′ = H (4a); H, CH₃ (4b); C₆H₅ (4c); CH₃, C₆H₅ (4d) OCH₃ (4e); and OC₂H₅ (4f), respectively. The ligand L is generated in situ through the condensation of 3,5-HRR′pz with acetonitrile under the influence of [(η⁶-p-cymene)RuCl₂]₂. The complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂2 reacts with pyrazole ligands in acetonitrile to yield bis-pyrazole derivatives such as [(η⁶-C₆Me₆)Ru (3,5-HRR′pz)₂Cl](BF₄) (5a-b), where R, R′ = H (5a); H, CH₃ (5b), as well as dimeric complexes of pyrazole substituted chloro bridged derivatives [{(η⁶-C₆Me₆)Ru(μ-Cl) (3,5-HRR′pz)}₂](BF₄)₂ (5c-g), where R, R′ = CH₃ (5c); C₆H₅ (5d); CH₃, C₆H₅ (5e); OCH₃ (5f); and OC₂H₅ (5g), respectively. These complexes were characterized by FT-IR and FT-NMR spectroscopy as well as analytical data. The molecular structures¹ of representative complexes [(η⁶-C₆Me₆)Ru{3(5)-Hmpz}₂Cl]⁺5b, [(η⁶-C₆Me₆)Ru(μ-Cl)(3,5-Hdmpz)]₂²⁺5c and [(η⁶-C₆Me₆)Ru(μ-Cl){3(5)Me,5(3)Ph-Hpz}]₂²⁺5e were established by single crystal X-ray diffraction studies.     

One ligand different metal complexes: Biological studies of titanium(IV), tin(IV) and gallium(III) derivatives with the 2,6-dimethoxypyridine-3-carboxylato ligand

The reaction of 2,6-dimethoxypyridine-3-carboxylic acid (DMPH) with different precursors [Ti(η⁵-C₅H₅)₂Cl₂], [Ti(η⁵-C₅H₄Me)₂Cl₂], [Ti(η⁵-C₅H₄SiMe₃)(η⁵-C₅H₅)Cl₂], [Ti(η⁵-C₅Me₅)Cl₃], SnMe₃Cl and Ga^tBu₃ yielded the complexes [Ti(η⁵-C₅H₅)₂(DMP-κO)₂] (1), [Ti(η⁵-C₅H₄Me)₂(DMP-κO)₂] (2), [Ti(η⁵-C₅H₄SiMe₃)(η⁵-C₅H₅)(DMP-κO)₂] (3), [Ti(η⁵-C₅Me₅)(DMP-κ²O,O′)₃] (4), [SnMe₃(μ-DMP-κO:κO′)]_∞ (5), and [Ga^tBu₂(μ-DMP-κO:κO′)]₂ (6). 1-6 have been characterized by spectroscopic methods and the molecular structure of the complexes 1, 2, 3, 5 and 6 have been determined by X-ray diffraction studies. The cytotoxic activity of 1-6 was tested against the tumour cell lines human adenocarcinoma HeLa, human myelogenous leukaemia K562, human malignant melanoma Fem-x and human breast carcinoma MDA-MB-361. The results of this study show a higher cytotoxicity of the tin(IV) and gallium(III) derivatives in comparison to their titanium(IV) counterparts. Furthermore, the different titanium compounds showed differences in their cytotoxicities with a higher activity of complex 4 (mono-(cyclopentadienyl) derivative) compared to that of 1-3 (bis-(cyclopentadienyl) complexes). A qualitative UV-vis study of the interactions of these complexes with DNA has also been carried out.