Syntheses of [(η 6- p -cymene)Ru(EPh3)2Cl]+ complexes and molecular structure of chloro(η 6- p -cymene)-bis(triphenylphosphine)ruthenium(II) tetrafluoroborate (E = P,As and Sb)

The reaction of [(η⁶-p-cymene)RuCl₂]₂ with excess EPh₃ (E = P, As, Sb) in methanol in the presence of ammonium tetrafluoroborate leads to the formation of complexes of the type [(η⁶-p-cymene)Ru(EPh₃)₂Cl]BF_4, E = P (1), As (2), Sb (3), which arise through cleavage of the chloride bridges. These complexes were characterized by spectral and analytical data. The crystal structure of 1 was solved by single-crystal X-ray crystallography in order to establish the exact structure in the solid state. The complex crystallizes in monoclinic space group P2₁/n (#14) with a = 12.42500(10), b = 30.1925(3), c = 11.06530(10)?Å, β = 103.1470(10)°.     

Preparation, Structure, and Thermal Decomposition of Co(II) Complexeswith 2,3- and 2,5-Dichlorobenzoic Acid and Imidazole

Summary.  The reaction products of Co(II)-2,3- and -2,5-dichlorobenzoate with imidazole (1, 2; CoL ₂⋯2imdċ2H₂O, L=C₇H₃Cl₂O, imd=imidazole) were characterized by their spectroscopic and thermochemical properties. The compounds crystallize in the monoclonic system with space group = P2₁/c, a=13.848(3), b=12.841(3) ?, c= 7.064(2) ?, β=98.12 °, V=1243.5(4) ?³, Z=2 for 1 and space group =P2₁/n, a=13.293(3), b= 6.964(2), c=13.800(3) ?, β=108.92(3) °, V=1208.6(4) ?³, Z=2 for 2. The complexes lose their crystal water in one step at 333 K and subsequently decompose to CoO with intermediate formation of Co₃O₄. Received August 9, 1999. Accepted (revised) February 11, 2000     

Preparation, Structure, and Thermal Decomposition of Co(II) Complexeswith 2,3- and 2,5-Dichlorobenzoic Acid and Imidazole

 The reaction products of Co(II)-2,3- and -2,5-dichlorobenzoate with imidazole (1, 2; CoL ₂⋯2imdċ2H₂O, L=C₇H₃Cl₂O, imd=imidazole) were characterized by their spectroscopic and thermochemical properties. The compounds crystallize in the monoclonic system with space group = P2₁/c, a=13.848(3), b=12.841(3) ?, c= 7.064(2) ?, β=98.12 °, V=1243.5(4) ?³, Z=2 for 1 and space group =P2₁/n, a=13.293(3), b= 6.964(2), c=13.800(3) ?, β=108.92(3) °, V=1208.6(4) ?³, Z=2 for 2. The complexes lose their crystal water in one step at 333 K and subsequently decompose to CoO with intermediate formation of Co₃O₄.     

Density functional theory analysis of some triple-decker sandwich complexes of iron containing cyclo-P5 and cyclo-As5 ligands

Structure and bonding in triple-decker cationic complexes [(η⁵-Cp)Fe(μ,η:η⁵-E₅) Fe(η⁵-Cp)]⁺ (1: E = CH, 2: E = P, 3: E = As) and [(η⁵-Cp)Fe(μ,η:η⁵-Cp)Fe(η⁵-E₅)]⁺ (E = P, As) are examined by density functional theory (DFT) calculations at the B3LYP/6-31+G* level. These species exhibit the lowest energy when all the three ligands are eclipsed. In the complexes with bifacially coordinated cyclo-E₅, the perfectly eclipsed D_5h sandwich structure a is found to be a potential minimum. The energy difference between the fully eclipsed and the staggered conformations b and c are within 1.0, 2.1, and 6.3 kcal/mol, respectively, for E = CH, P, and As. The isomeric species with monofacially coordinated cyclo-E₅ (E =P, As), [(η⁵ -Cp)Fe(μ,η :η⁵-Cp)Fe(η⁵-E₅)]⁺ are predicted to be about 30 and 60 kcal/mol higher in energy , respectively, for E = P and As. The calculations predict that the bifacially coordinated cyclo-E₅ (E =P, As) undergoes significant ring expansion leading to ``loosening of bonds' as observed experimentally. The consequent loss of aromaticity in the central cyclo-E₅ indicates that significant π-electron density from the ring can be directed towards bonding with the iron centers on both sides. The diffuse nature of the π-orbitals of cyclo-P₅ and cyclo-As₅ can lead to better overlap with the iron d-orbitals and result in stronger bonding. This is reflected in the bond order values of 0.377 and 0.372 for the Fe-P and Fe-As bonds in 2a and 3a, respectively. The natural population analysis reveals that the Fe atom that is coordinated to a cyclo-E₅ (E = P, As) possesses a negative charge of −0.23 to −0.38 units due to transfer of electron density from the inorganic ring to the metal center.     

X-ray study of the third polymorphic structure of μ-oxo-bis[(octaethylporphinato)iron(III)]: [(OEPFe)2O)]

Exposure of a dichloromethane solution of [OEPFe^IIICl], where OEP is the dianion of octaethylporphyrin, to dioxygen results in its transformation into the μ-oxo bridged compound [(OEPFe)₂O)]. The structure of [(OEPFe)₂O)] is determined by X-ray diffraction analysis. It contains binuclear centrosymmetric [(OEPFe)₂O]. The Fe atom is five-coordinated to four N atoms of the porphyrin ring and to one bridging O atom. The compound is characterized by an average Fe-N bond length of 2.096 ?. The Fe-O bond distance is 1.7739(12) ?, the Fe-O-Fe bond angle is 180.0° and the two porphyrin rings are parallel. Crystal data: triclinic crystal system, a = 10.915(4) ?, b = 12.951(4) ?, c = 13.403(4) ?, α = 118.06(1)°, β = 100.33(1)°, Γ = 102.43°, space group, V = 1144.5(1) ?³, Z = 1.     

Arene ruthenium complexes of the thermally resistant ligand tri-2-pyridylamine

Summary The degradation-resistant ligand tri-2-pyridylamine (tripyam) (1) forms a variety of stable ruthenium complexes. Reaction of (1) with RuCl₂(PPh₃)₃ yields the complex RuCl₂(PPh₃)(tripyam) (2) and, upon prolonged heating in pyridine, forms RuCl₂(py)(tripyam) (3). Complexes (2) and (3) display unusual thermal stability, resisting degradation at temperatures of 270 °C. Reaction of (2) with two equivalents of AgSbF₆ in water yields the solvento complex [Ru(PPh₃)(tripyam)(OH₂)₂] (SbF₆)₂ (2a). Reaction of (1) with RuCl₃·H₂O also yields the trichloro complex RuCl₃(tripyam) (4). The organometallic precursor [RuCl₂(p-cymene)]₂ reacts with (1) and either two or four equivalents of AgSbF₆ to yield [RuCl(p-cymene)( ²-tripyam)]SbF₆ (5) and [Ru(p-cymene) ( ³-tripyam)](SbF₆)₂ (6), respectively. Each of these complexes has been characterized by spectroscopic techniques and, in the case of (5), by single-crystal X-ray diffraction.     

Anticancer activity of multinuclear arene ruthenium complexes coordinated to dendritic polypyridyl scaffolds

The rational development of multinuclear arene ruthenium complexes (arene = p-cymene, hexamethylbenzene) from generation 1 (G¹) and generation 2 (G²) of 4-iminopyridyl based poly(propyleneimine) dendrimer scaffolds of the type, DAB-(NH₂)_n (n = 4 or 8, DAB = diaminobutane) has been accomplished in order to exploit the ‘enhanced permeability and retention’ (EPR) effect that allows large molecules to selectively enter cancer cells. Four compounds were synthesised, i.e. [{(p-cymene)RuCl₂}₄G¹] (1), [{(hexamethylbenzene)RuCl₂}₄G¹] (2), [{(p-cymene)RuCl₂}₈G²] (3), and [{(hexamethylbenzene)RuCl₂}₈G²] (4), by first reacting DAB-(NH₂)_n with 4-pyridinecarboxaldehyde and subsequently metallating the iminopyridyl dendrimers with [(p-cymene)RuCl₂]₂ or [(hexamethylbenzene)RuCl₂]₂. The related mononuclear complexes [(p-cymene)RuCl₂(L)] (5) and [(hexamethylbenzene)RuCl₂(L)] (6) were obtained in a similar manner from N-(pyridin-4-ylmethylene)propan-1-amine (L). The molecular structure of 5 has been determined by X-ray diffraction analysis and the in vitro anticancer activities of the mono-, tetra- and octanuclear complexes 1–6 studied on the A2780 human ovarian carcinoma cell line showing a close correlation between the size of the compound and cytotoxicity.