Complexes n-Bu4N Research Articles

Cis-Tetrachlorido-bis(indazole)osmium(iv) and its osmium(iii) analogues: paving the way towards the cis-isomer of the ruthenium anticancer drugs KP1019 and/or NKP1339.

The relationship between cis-trans isomerism and anticancer activity has been mainly addressed for square-planar metal complexes, in particular, for platinum(ii), e.g., cis- and trans-[PtCl2(NH3)2], and a number of related compounds, of which, however, only cis-counterparts are in clinical use today. For octahedral metal complexes, this effect of geometrical isomerism on anticancer activity has not been investigated systematically, mainly because the relevant isomers are still unavailable. An example of such an octahedral complex is trans-[RuCl4(Hind)2]-, which is in clinical trials now as its indazolium (KP1019) or sodium salt (NKP1339), but the corresponding cis-isomers remain inaccessible. We report the synthesis of Na[cis-OsIIICl4(κN2-1H-ind)2]·(Na[1]) suggesting a route to the cis-isomer of NKP1339. The procedure involves heating (H2ind)[OsIVCl5(κN1-2H-ind)] in a high boiling point organic solvent resulting in an Anderson rearrangement with the formation of cis-[OsIVCl4(κN2-1H-ind)2] ([1]) in high yield. The transformation is accompanied by an indazole coordination mode switch from κN1 to κN2 and stabilization of the 1H-indazole tautomer. Fully reversible spectroelectrochemical reduction of [1] in acetonitrile at 0.46 V vs. NHE is accompanied by a change in electronic absorption bands indicating the formation of cis-[OsIIICl4(κN2-1H-ind)2]- ([1]-). Chemical reduction of [1] in methanol with NaBH4 followed by addition of nBu4NCl afforded the osmium(iii) complex nBu4N[cis-OsIIICl4(κN2-1H-ind)2] (nBu4N[1]). A metathesis reaction of nBu4N[1] with an ion exchange resin led to the isolation of the water-soluble salt Na[1]. The X-ray diffraction crystal structure of [1]·Me2CO was determined and compared with that of trans-[OsIVCl4(κN2-1H-ind)2]·2Me2SO (2·2Me2SO), also prepared in this work. EPR spectroscopy was performed on the OsIII complexes and the results were analyzed by ligand-field and quantum chemical theories. We furthermore assayed effects of [1] and Na[1] on cell viability and proliferation in comparison with trans-[OsIVCl4(κN1-2H-ind)2] [3] and cisplatin and found a strong reduction of cell viability at concentrations between 30 and 300 μM in different cancer cell lines (HT29, H446, 4T1 and HEK293). HT-29 cells are less sensitive to cisplatin than 4T1 cells, but more sensitive to [1] and Na[1], as shown by decreased proliferation and viability as well as an increased late apoptotic/necrotic cell population.

Trichloro-mono- β -diketonato oxorhenium(V) complexes: synthesis, characterization and crystal structure

Oxorhenium(V) complexes of β-diketonate systems have been synthesized and isolated in pure form. The red complexes n-Bu4N[ReO(R1COCHCOR2)Cl3] (acac, R1=R2=CH3; bzac, R1=CH3 and R2=C6H5; bzbz, R1=R2=C6H5) have been characterized by elemental analyses, spectroscopic and other physico-chemical tools. One complex, n-Bu4N[ReO(bzbz)Cl3] (1c) has been subjected to single-crystal X-ray analysis. In the structure of the anion, the metal has a six-coordinate octahedral environment in which the bidentate β-diketone ligand is cis and trans to the terminal oxygen.

Nickel Complexes Based on Thiophenedithiolate Ligands − Magnetic Properties of Metallocenium Salts

The nickel complex nBu4N[Ni(α-tpdt)2] (2) (α-tpdt = 2,3-thiophenedithiolate) has been prepared and characterized. A salt of this monoanionic paramagnetic complex, [Fe(Cp*)2][Ni(α-tpdt)2] (3), was obtained with decamethylferrocene, crystallizing in the monoclinic space group P21/a with a = 15.443(3), b = 10.237(1), c = 20.360(2) Å, β = 107.54(1)°, V = 3069.1(7) Å3, Z = 4. Its structure consists of alternating cationic and anionic layers, with short interlayer contacts defining alternating cation−anion chains. Magnetic characterization of 3 at low applied magnetic fields revealed an antiferromagnetic transition at TN = 2.56 K. Below TN, 3 displays a metamagnetic behaviour with a critical field of 0.07 T at 1.6 K. The magnetic properties of this compound are compared with those of the analogous salts with diamagnetic gold dithiolate [Fe(Cp*)2][Au(α-tpdt)2] (4), and diamagnetic decamethylcobaltocenium, [Co(Cp*)2][Ni(α-tpdt)2] (5), which are also reported. This comparison shows that the ferromagnetic interactions observed in 3 are due to cation−anion intrachain interactions.

Increasing the Lipophilic Character of Tetraphenylborate Anions through Silyl Substituents

Trimethylsilyl- and dimethyl(1H,1H,2H,2H-perfluorooctyl)silyl substituents have been introduced in the para position of tetraphenylborate anions, resulting in enhanced solubility of their complexes n-Bu4N[B(C6H4SiMe2R-4)4] (R = Me, CH2CH2C6F13) and [Rh(dppe)2][B(C6H4SiMe2R-4)4] (dppe = 1,2-bis(diphenylphosphino)ethane, R = Me, CH2CH2C6F13) in apolar organic solvents.

Gold complexes with dithiothiophene ligands: a metal based on a neutral molecule.

The gold complexes n-Bu4N[Au(alpha-tpdt)2] (5), n-Bu4N[Au(dtpdt)2] (4) and n-Bu4N[Au(tpdt)2] (6) based on new dithiothiophene ligands (alpha-tpdt= 2,3-thiophenedithiolate, dtpdt=2,3-dihydro-5,6-thiophenedithiolate and tpdt = 3,4-thiophenedithiolate) have been prepared and characterised. These gold(III) complexes are diamagnetic, but they can be oxidised with iodine to the paramagnetic compounds [Au(alpha-tpdt)2] (8), [Au(dtpdt)2] (7) and n-Bu4N[[Au(tpdt)2]n-2] (9), which were isolated as fine powders and which exhibit paramagnetic susceptibilities that are almost temperature independent with room temperature values of 2.5 x 10(-4), 2.0 x 10(-4) and 5 x 10(-4) emu x mol(-1), respectively. Interestingly, the neutral complex [Au(alpha-tpdt)2] (8) as a polycrystalline sample displays the properties of a metallic system with a room temperature electrical conductivity of 6 S x cm(-1) and a thermoelectric power of 5.5 microVK(-1); this is the first time that this metallic property has been observed in a molecular system based on a neutral species.

The synthesis, characterization and substitution reactions of the mixed ligand technetium(I) nitrosyl complex trans—trans-[(NO)(NCCH3)Cl2(PPh3)2Tc

The techneium—nitrosyl complex n-Bu4N[Tc(NO)Cl4] reacts with excess triphenylphospine in refluxing acenotonitrile to give the Tc(I) mixed ligand complex [Tc(NO)Cl2(PPh3)2NCCH3 in good yield. The IR spectrum of this complex displays an absorption at 1690 cm−1 which is associated with v(NO). The FAB(+) mass spectrum shows the fragment of 723 mz which corresponds to [Tc(NO)Cl2(PPh3)2]+ which is generated from the loss of the acetonitrile ligand. The 1HNMRR spectrum of this species displays equivalent trans-triphenylphosphine ligands; however because of the liability of the acetnitrile ligand, two signals are observed from the coordinated and dissociated acetonitrile protons. The analogous reaction in the methanol gives the methanol adduct [Tc(NO)Cl2(PPh3)2HOCH3]. When pyridine is employed as solvent, the tris-pyridine complex [Tc(NO)Cl2(py)3] is isolated as the major product, with no phosphine coordination. The IR spectrum of this complex shows an absorption at 1688 cm−1 which is associated with v(NO). The FAB(+) mass spectrum shows the fragment of 436 m/z which corresponds to the parent ion [Tc(NO)Cl2(py)3]+. This diamagnetic Tc(I) complex displays a well resolved, narrow-lined 1H NMR spectrum. Crystal data for [Tc(NO)Cl2(py)3]∗d2CH3CN: monoclinic space group C2/c, (No. 15), a = 19.182(1), b = 10.8725(8), c = 11.9371(8) A, β = 116.580(7)°,V = 2226.5(6) A3, with Dcalc = 1.543 g cm−3 to give Z = 4. structure solution based on 2689 reflections converged at R = 0.025, Rw = 0.030, GOF = 1.41. The reaction chemistry of the acetonitrile adduct [Tc(NO)Cl2(PPh3)2NCCH3] with pyridine, 3,5-lutidine, bipyridine, phenanthroline and terpyridine is also presented.

Electrochemistry of rhenium(V) complexes with N-(2-hydroxyphenyl)salicylideneiminate as schiff base ligand

The anodic and cathodic behaviour of the rhenium(V) complexes nBu 4N[ReOCl 3(HOPhSal)], nBu 4N[ReOCl 2(OPhSal)], [ReOCl(OPhSal)(MeOH)] and [ReOCl(OPhSal)(PMe 2Ph)] in acetonitrile was studied using platinum and mercury electrodes. Cyclic voltammetry and controlled potential coulometry were the main electroanalytical techniques employed. The nature of the electrolysis products as well as the mechanisms of the electrode oxidation and reduction processes were investigated. In particular a complex of rhenium(VI) containing the group ReO 4+ and complexes of rhenium(IV) with ReO 2+ core were electrochemically synthesized. They were characterized by elemental analysis, IR spectroscopy, magnetic susceptibility and conductivity measurements.