Ruthenium(II) complexes with ferrocene-modified arene ligands: synthesis and electrochemistry

Phosphorus-Nitrogen Compounds. Part 65. Novel diansa-spiro-cyclotetraphosphazenes: synthesis, characterization, bioactivity and electrochemical properties, fabrication of dye-sensitized solar cell studies

In this investigation, the substitution reaction of octachlorocyclotetraphosphazene, N4P4Cl8 (tetramer, OCCP, 1) with sodium 3-(N-ferrocenylmethylamino)-1-propanoxide (L1) was found to yield the compounds, 2,4-ansa- (2) and spiro- (2) cyclotetraphosphazene derivatives. The...

Induction of Cytotoxicity in Pyridine Analogues of the Anti-metastatic Ru(III) Complex NAMI-A by Ferrocene Functionalization

A series of novel ferrocene (Fc) functionalized Ru(III) complexes was synthesized and characterized. These compounds are derivatives of the anti-metastatic Ru(III) complex imidazolium [trans-RuCl4(1H-imidazole) (DMSO-S)] (NAMI-A) and are derived from its pyridine analogue (NAMI-Pyr), with direct coupling of Fc to pyridine at the 4 or 3 positions, or at the 4 position via a two-carbon linker, which is either unsaturated (vinyl) or saturated (ethyl). Electron paramagnetic resonance (EPR) and UV-vis spectroscopic studies of the ligand exchange processes of the compounds in phosphate buffered saline (PBS) report similar solution behavior to NAMI-Pyr. However, the complex with Fc substitution at the 3 position of the coordinated pyridine shows greater solution stability, through resistance to the formation of oligomeric species. Further EPR studies of the complexes with human serum albumin (hsA) indicate that the Fc groups enhance noncoordinate interactions with the protein and help to inhibit the formation of protein-coordinated species, suggesting the potential for enhanced bioavailability. Cyclic voltammetry measurements demonstrate that the Fc groups modestly reduce the reduction potential of the Ru(III) center as compared to NAMI-Pyr, while the reduction potentials of the Fc moieties of the four compounds vary by 217 mV, with the longer linkers giving significantly lower values of E1/2. EPR spectra of the compounds with 2-carbon linkers show the formation of a high-spin Fe(III) species (S = 5/2) in PBS with a distinctive signal at g = 4.3, demonstrating oxidation of the Fe(II) ferrocene center and likely reflecting degradation products. Density functional theory calculations and paramagnetic (1)H NMR describe delocalization of spin density onto the ligands and indicate that the vinyl linker could be a potential pathway for electron transfer between the Ru and Fe centers. In the case of the ethyl linker, electron transfer is suggested to occur via an indirect mechanism enabled by the greater flexibility of the ligand. In vitro assays with the SW480 cell line reveal cytotoxicity induced by the ruthenium ferrocenylpyridine complexes that is at least an order of magnitude higher than the unfunctionalized complex, NAMI-Pyr. Furthermore, migration studies with LNCaP cells reveal that Fc functionalization does not reduce the ability of the compounds to inhibit cell motility. Overall, these studies demonstrate that NAMI-A-type compounds can be functionalized with redox-active ligands to produce both cytotoxic and anti-metastatic activity.

Functionalized arene-ruthenium(II) complexes: dangling vs. tethering side chain

The reactivity of compounds [RuCl2(η(6)-C6H5OCH2CH2OH)(L)] (L = phosphine or phosphite) towards the chloride abstractor AgSbF6 has been investigated. Thus, the treatment of the triphenylphosphite complex [RuCl2(η(6)-C6H5OCH2CH2OH){P(OPh)3}] with one equivalent of AgSbF6 gave rise to the formation of the dinuclear dichloro-bridged species [{Ru(μ-Cl)(η(6)-C6H5OCH2CH2OH){P(OPh)3}}2](2+) as the hexafluoroantimonate salt. On the other hand, the triphenylphosphine analog [RuCl2(η(6)-C6H5OCH2CH2OH)(PPh3)] led, under the same experimental conditions, to the di-ruthenium derivative [{RuCl(η(6)-C6H5OCH2CH2OH)(PPh3)}2(μ-Cl)][SbF6] containing only one Cl-bridge. In sharp contrast, treatment of precursors [RuCl2(η(6)-C6H5CH2CH2CH2OH)(L)] (L = P(OPh)3, PPh3, P(OEt)3) with AgSbF6 resulted in the clean formation of the tethered compounds [RuCl{η(6):κ(1)(O)-C6H5CH2CH2CH2OH}(L)][SbF6]. The differences in reactivity observed have been rationalized by theoretical calculations.

Dichlorido(furfurylamine-κN)(η6-hexamethylbenzene)ruthenium(II)

The single-crystal X-ray structure analysis of [RuCl₂(C₁₂H₁₈)(C₅H₇NO)] reveals a distorted piano-stool geometry around the Ru^II atom, with a hexa­methyl­benzene ligand, two chloride ligands and a furfuryl­amine ligand, the latter coordinating through the amine group. In the crystal, a dimeric structure is observed as a result of N—H⋯Cl inter­actions between two symmetry-related mol­ecules.

Dichlorido[1-(2-chloroethyl)-3-(pyridin-4-ylmethyl-κN)urea](η6-hexamethylbenzene)ruthenium(II) chloroform monosolvate

The Ru^II atom in the title compound, [RuCl₂(C₁₂H₁₈)(C₉H₁₂ClN₃O)]·CHCl₃, exhibits a typical piano-stool coordination, defined by a hexa­methyl­benzene ligand, two chloride ligands and a pyridyl­urea ligand coordinated through the pyridine N atom. In the crystal, a dimeric structure is observed due to two strong N—H⋯Cl inter­actions between the NH groups of urea and the two chloride ligands of neighbouring mol­ecules. In addition, the C=O group of the urea moiety inter­acts with the solvent mol­ecule through weak C—H⋯O interactions.

31P NMR study of the stoichiometry, stability and thermodynamics of complex formation between palladium(II) acetate and bis(diphenylphosphino)ferrocene

The complexation reaction between palladium (II) acetate, and 1,1'-bis(diphenylphosphino)ferrocene, DPPF, was investigated in two different deuterated solvents CDCl(3) and DMSO at various temperatures using (31)P NMR spectroscopy. The exchange between free and complexed DPPF is slow on the NMR time scale and consequently, two (31)P NMR signals were observed. At metal ion-to-ligand mole ratio larger than 1, only one (31)P NMR signal was observed, indicating the formation of a 1:1 Pd(2+)-DPPF complex in solution. The formation constant of the resulting 1:1 complexes was determined from the integration of two (31)P signals. The values of the thermodynamic parameters (DeltaH, DeltaS and DeltaG(298)) for complexation were determined from the temperature dependence of stability constants. It was found that, in both solvents, the resulting complex is mainly entirely enthalpy stabilized and the DeltaH compensates the TDeltaS contribution.

Dichlorido(η-toluene)[tris-(4-methoxy-phen-yl)phosphine]ruthenium(II)

In the title compound, [RuCl₂(C₇H₈)(C₂₁H₂₁O₃P)], the Ru^II atom possesses a pseudo-octa­hedral geometry and the metrical parameters around the metallic core compare well with those of similar three-legged-piano-stool complexes.