Oxygenation of thiolates to S-bonded sulfinate in an iron III complex related to nitrile hydratase

Air oxidation of the iron(III) complex derived from (2-mercaptoisobutyryl)-4,5-dichloro-O-phenylenediamine in the presence of Et4NCN afforded the corresponding disulfinato species. With two carboxamido nitrogens trans to two S-bonded sulfinates, this complex mimics the disulfinate inactive form of Fe-NHase.     

Synthesis and characterization of some novel ruthenium(II) complexes containing thiolate ligands

Reactions of the ruthenium complexes [RuH(CO)Cl(PPh₃)₃] and [RuCl₂(PPh₃)₃] with hetero-difunctional S,N-donor ligands 2-mercapto-5-methyl-1,3,5-thiadiazole (HL¹), 2-mercapto-4-methyl-5-thiazoleacetic acid (HL²), and 2-mercaptobenzothiazole (HL³) have been investigated. Neutral complexes [RuCl(CO)(PPh₃)₂(HL¹)] (1), [RuCl(CO)(PPh₃)₂(HL²)] (2), [RuCl(CO)(PPh₃)₂(HL³)] (3), [Ru(PPh₃)₂(HL¹)₂] (4), [RuCl(PPh₃)₃(HL²)] (5), and [RuCl(PPh₃)₃(HL³)] (6) imparting κ²-S,N-bonded ligands have been isolated from these reactions. Complexes 1 and 4 reacted with diphenyl-2-pyridylphosphine (PPh₂Py) to give neutral κ¹-P bonded complexes [RuCl(CO)(κ¹-P-PPh₂Py)₂(HL¹)] (7), and [Ru(κ¹-P-PPh₂Py)₂(HL¹)₂] (8). Complexes 1-8 have been characterized by analytical, spectral (IR, NMR, and electronic absorption) and electrochemical studies. Molecular structures of 1, 2, 4, and 7 have been determined crystallographically. Crystal structure determination revealed coordination of the mercapto-thiadiazole ligands (HL¹-HL³) to ruthenium as κ²-N,S-thiolates and presence of rare intermolecular S-S weak bonding interaction in complex 1.     

Complexes of ruthenium(II) and -(III) with dimethylsulphoxide—III. Bis-iodo-tetrakis- dimethylsulphoxide ruthenium(II) and some other iodo complexes of ruthenium(II)

The ruthenium(II) complex [RuI₂(Me₂SO)₄] was synthesized and characterized. The Me₂SO ligands are all S-bonded. Reactions of RuI₂(Me₂SO)₄ with ligands containing P, N and S donor atoms have been carried out and the complexes obtained were characterized using different physical methods. [RuI₂L₄] (L= CH₃CN, Me₂SO and py), [RuI₂(CH₃CN)₂(PPh₃)₂] and [RuI₂(CS)(PPh₃)₃] have been synthesized using RuI₃ as the source material and characterized as above.     

Carbon-sulfur bond formation via alkene addition to an oxidized ruthenium thiolate

Bulk oxidation of [Ru(DPPBT)3], 1b, (DPPBT = 2-diphenylphosphinobenzenethiolate) in the presence of ethylene yields [(ethane-1,2-diylbis(thio-2,1-phenylene)diphenylphosphine) ruthenium(II)] hexafluorophosphate, [2a]PF6, from the addition of the alkene across cis sulfur sites. During oxidation, the absorption bands of 1b at 540, 797, and 1041 nm decrease in intensity. The resulting complex [2a]+ displays a single redox couple at +804 mV. The +ESI-MS of [2a]+ shows a parent ion peak at m/z = 1009.1013, and the 31P NMR spectrum displays chemical shift values of delta(1) = 61.0, delta(2) = 40.3, and delta(3) = 37.5 with coupling constants of J(12) approximately J(13) approximately 30 Hz and J(23) = 304 Hz. Oxidation of [2a]+ by one electron at a holding potential of +1000 mV yields [(ethane-1,2-diylbis(thio-2,1-phenylene)diphenyl phosphine)ruthenium(III)] hexafluorophosphate, [2b][PF6]2. The EPR of [2b][PF6]2 displays a rhombic signal with g(1) = 2.09, g(2) = 2.04, and g(3) = 2.03. Oxidation of 1b in the presence of alkenes including 1-hexene, styrene, cyclohexene, and norbornene yields products similar to [2a]+. Each of these products was further oxidized to an analogue of [2b]2+. Complex [2a]+ was also prepared, as the bromide salt, from [PPN][Ru(DPPBT)3] (PPN [1a]; PPN = bis(triphenylphosphoranylidene)ammonium) and 1,2-dibromoethane. The complex [2a]Br crystallizes as thin yellow plates in the monoclinic space group P21/c with unit cell dimensions of a = 10.2565(9) A, b = 13.2338(12) A, c = 38.325(3) A, and beta = 93.3960(10) degrees.     

Copper(II) and ruthenium(II)/(III) Schiff base complexes

Metal complexes of general formula [Cu(L)](ClO4)2, [Ru(L)(PPh3)2]Cl2 and [Ru(L)(PPh3)Cl]Cl2[L = 1,4-di- (o-benzylidiminophenoxy/benzylidiminophenylthio)butane] containing N2O2 or N2S2 donor atoms have been prepared and characterised by spectral, magnetic and cyclic voltammetric studies. The rhombic nature of the e.s.r. spectra of the RuIII complexes indicates an asymmetry in the electronic environment around the Ru atom. e.s.r. spectra of the CuII complexes show a typical four-line spectrum with approximate tetrahedral distortion. The observed low A values in the CuII complexes, of the order of 132–160 × 10–4cm–1, indicates a tetrahedrally distorted square planar structure.The influence of modified ligands is reflected in the metal-centered redox potentials. CuII complexes having the N2S2 chromophore, in MeCN on a glassy carbon electrode, undergo quasi-reversible reduction in the 540–680 mV range. A depression in E1/2 values for the open chain N2S2 chromophoric macrocyclic CuII complexes, compared to electronically similar cyclic tetradentate CuII analogues, is due to the increased stabilization of the CuI state by added flexibility provided through the open chain donor sites.     

Unique formation of a pentanuclear lanthanum(III) thiolate oxide cluster via control of hydrolysis

The reaction of [(TMS)2N]3La(mu-Cl)Li(THF)3 (1) and HSPh produced a bimetallic complex [{(TMS)2N}2La(THF)]2(mu-SPh)(mu-Cl)] (2). Compound [{(TMS)2N}2La5O(SPh)10LiCl2(THF)6] (3) was prepared by control of the hydrolysis of 2 and LiCl or 1 and HSPh with the proper amount of water. 1 was treated first with 1/6 equiv of H2O and then with equimolar HSPh; a polymeric complex [{(TMS)2N}2(mu-SPh)La(mu-SPh)Li(THF)2](infinity) (4) was isolated. 3 contains a central [(mu-SPh)4(mu3-SPh)2{La(THF)}4(mu3-O)]4+ tetrahedral fragment in which two La atoms are linked by a pair of mu-SPh- and mu3-Cl- ligands to a [{(TMS)2N}2La]+ fragment, while the other two are bridged by two mu-SPh- ligands to a [Li(THF)2]+ fragment, forming a bee-shaped structure.     

Photoinduced ligand release in a ruthenium(II)-cobalt(III) heterodinuclear system

Two Ru(II)-Co(III) heterodinuclear complexes have been synthesised as model complexes for photoactivated cytotoxins. Photoinduced ligand release has been demonstrated and the rate shown to depend on dioxygen concentration. Emission lifetimes and quantum yields are reported. These results validate the concept and justify further work to synthesise systems containing cytotoxic ligands.     

Mixed complexes of ruthenium(III) and ruthenium(II) with triphenylphosphine or triphenylarsine and other ligands

The reactions of [RuCl₃(AsPh₃)₃] with ligands containing nitrogen (ammonia, hydrazines, amine and thiocyanate) and oxygen (carboxylates) and the reactions of β-diketones (acetylacetone, dibenzoylmethane and benzoylacetone) with [RuCl₂(PPh₃)₂]_n and [RuCl₂(AsPh₃)₂]₂ have been studied. Apart from this, a new Ru(III) complex, [RuBr₃(AsPh₃)₃] has also been synthesized. The compounds obtained have been characterised by analyses, conductivity and magnetic measurements, molecular weight and spectral studies (IR and visible). An equilibrium between hexacoordinated and pentacoordinated species is suggested on the basis of electronic spectral studies.     

General synthesis of (salen)ruthenium(III) complexes via N...N coupling of (salen)ruthenium(VI) nitrides

Reaction of [Ru (VI)(N)(L (1))(MeOH)] (+) (L (1) = N, N'-bis(salicylidene)- o-cyclohexylenediamine dianion) with excess pyridine in CH 3CN produces [Ru (III)(L (1))(py) 2] (+) and N 2. The proposed mechanism involves initial equilibrium formation of [Ru (VI)(N)(L (1))(py)] (+), which undergoes rapid N...N coupling to produce [(py)(L (1))Ru (III) N N-Ru (III)(L (1))(py)] (2+); this is followed by pyridine substituion to give the final product. This ligand-induced N...N coupling of Ru (VI)N is utilized in the preparation of a series of new ruthenium(III) salen complexes, [Ru (III)(L)(X) 2] (+/-) (L = salen ligand; X = H 2O, 1-MeIm, py, Me 2SO, PhNH 2, ( t )BuNH 2, Cl (-) or CN (-)). The structures of [Ru (III)(L (1))(NH 2Ph) 2](PF 6) ( 6), K[Ru (III)(L (1))(CN) 2] ( 9), [Ru (III)(L (2))(NCCH 3) 2][Au (I)(CN) 2] ( 11) (L (2) = N, N'-bis(salicylidene)- o-phenylenediamine dianion) and [N ( n )Bu 4][Ru (III)(L (3))Cl 2] ( 12) (L (3) = N, N'-bis(salicylidene)ethylenediamine dianion) have been determined by X-ray crystallography.     

Synthesis and photophysics of one mononuclear Mn(III) and one dinuclear Mn(III,III) complex covalently linked to a ruthenium(II) tris(bipyridyl) complex

The preparation of donor (D)-photosensitizer (S) arrays, consisting of a manganese complex as D and a ruthenium tris(bipyridyl) complex as S has been pursued. Two new ruthenium complexes containing coordinating sites for one (2a) and two manganese ions (3a) were prepared in order to provide models for the donor side of photosystem II in green plants. The manganese coordinating site consists of bridging and terminal phenolate as well as terminal pyridyl ligands. The corresponding ruthenium-manganese complexes, a manganese monomer 2b and dimer 3b, were obtained. For the dimer 3b, our data suggest that intramolecular electron transfer from manganese to photogenerated ruthenium(III) is fast, k(ET) > 5 x 10(7) s(-)(1).     

Nonadiabatic, short-range, intramolecular electron transfer from ruthenium(II) to cobalt(III) complexes

The activation parameters reported for intramolecular electron-transfer between ruthenium(II) and cobalt(III) complexes have been corrected for the thermodynamic contributions of the entropy change for the reaction DeltaS0 to the entropy of activation DeltaS*, and it is concluded that these electron-transfers range from adiabatic (pyrazine bridge) to highly nonadiabatic. The electronic factors are about 20 times smaller than for diruthenium mixed-valence complexes. Spanning the metal-metal separation range of 7-14 A over which beta=0.7 A-1, the electron-transfer rates are dominated by the electronic factors, which change three times more with separation than do the nuclear factors.     

Ruthenium(III) and ruthenium(II) complexes containing triphenylarsine and other ligands

The reactions of [RuCl₃(AsPh₃)₃] with ligands containing nitrogen (alkyl and aryl cyanides, pyridine, α-picoline N.N′-bipyridyl, 1,10-phenanthroline), oxygen (ketones, aldehydes, N,N-dimethylformamide, tetrahydrofuran, dimethylsulphoxide and nitroalkanes) and sulphur (CS₂ and Me₂S) donor atoms have been studied. The reactions of [RuCl₃(AsPh₃)₃] with tetra alkyl and aryl ammonium and arsonium salts have also been explored. The compounds obtained have been characterised by analyses, conductivity measurements, magnetic measurements and IR spectra. The electronic spectra of the complexes are discussed in terms of possible structures. An equilibrium between hexacoordinated and pentacoordinated species is suggested on the basis of electronic spectral studies.     

From ruthenium(II) to iridium(III): 15 years of triads based on bis-terpyridine complexes

In order to mimic the photosynthetic reaction centre and better understand photoinduced electron transfer processes, a family of compounds has been studied for the past 15 years. These are transition metal complexes, M(tpy)(2) where tpy is a 2,2':6',2" terpyridine based ligand, bearing on one side a donor group and on the other side an acceptor group. The resulting triad molecules or their two-component reference compounds (donor-M(tpy)(2) and M(tpy)(2-acceptor) can contain Ru, Os, Rh or Ir as the metal centre and both visible-light non absorbing groups and porphyrins as donor and acceptor groups. This tutorial review will briefly present the different systems studied and the reasons that led to the preparation of new systems with improved performances.     

Effect of spin-orbit coupling on reduction potentials of octahedral ruthenium(II/III) and osmium(II/III) complexes

Reduction potentials of several M(2+/3+) (M = Ru, Os) octahedral complexes, namely, [M(H2O)6](2+/3+), [MCl6](4-/3-), [M(NH3)6](2+/3+), [M(en)3](2+/3+) [M(bipy)3](2+/3+), and [M(CN)6](4-/3-), were calculated using the CASSCF/CASPT2/CASSI and MRCI methods including spin-orbit coupling (SOC) by means of first-order quasi-degenerate perturbation theory. It was shown that the effect of SOC accounts for a systematic shift of approximately -70 mV in the reduction potentials of the studied ruthenium (II/III) complexes and an approximately -300 mV shift for the osmium(II/III) complexes. SOC splits the sixfold-degenerate (2)T(2g) ground electronic state (in ideal octahedral symmetry) of the M(3+) ions into the E((5/2)g) Kramers doublet and G((3/2)g) quartet, which were calculated to split by 1354-1573 cm(-1) in the Ru(3+) complexes and 4155-5061 cm(-1) in the Os(3+) complexes. It was demonstrated that this splitting represents the main contribution to the stabilization of the M(3+) ground state with respect to the closed-shell (1)A(1g) ground state in M(2+) systems. Moreover, it was shown that the accuracy of the calculated reduction potentials depends on the calculated solvation energies of both the oxidized and reduced forms. For smaller ligands, it involves explicit inclusion of the second solvation sphere into the calculations, whereas implicit solvation models yield results of sufficient accuracy for complexes with larger ligands. In such cases (e.g., [M(bipy)3](2+/3+) and its derivatives), very good agreement between the calculated (SOC-corrected) values of the reduction potentials and the available experimental values was obtained. These results led us to the conclusion that especially for Os(2+/3+) complexes, inclusion of SOC is necessary to avoid systematic errors of approximately 300 mV in the calculated reduction potentials.     

Coordination compounds of 2-mercapto-1-methylimidazole with platinum(II), palladium(II), rhodium(III) and ruthenium(III)

Summary Complexes of 2-mercapto-1-methylimidazole (TMZ) with Pt^II, Pd^II, Rh^III and Ru^III of the general formulae Pt(TMZ)₂Cl₂, Pd(TMZ)₄Cl₂. Rh(TMZ)Cl₃ and Ru(TMZ)Cl₃ have been obtained. The thermal stabilities of the compounds were estimated by derivatographic measurements and the electron-donating atom of the measurements and the electron-donating atom of the ligand was identified from the i.r. absorbtion spectra. Lattice constants for the Pt^II and Pd^II complexes were estimated from their x-ray powder diffraction patterns.     

DNA binding and topoisomerase II inhibitory activity of water-soluble ruthenium(II) and rhodium(III) complexes

Water-soluble piano-stool arene ruthenium complexes based on 1-(4-cyanophenyl)imidazole (CPI) and 4-cyanopyridine (CNPy) with the formulas [(eta6-arene)RuCl2(L)] (L = CPI, eta6-arene = benzene (1), p-cymene (2), hexamethylbenzene (3); L = CNPy, eta6-arene = benzene (4), p-cymene (5), hexamethylbenzene (6)) have been prepared by our earlier methods. The molecular structure of [(eta6-C6Me6)RuCl2(CNPy)] (6) has been determined crystallographically. Analogous rhodium(III) complex [(eta5-C5Me5)RhCl2(CPI)] (7) has also been prepared and characterized. DNA interaction with the arene ruthenium complexes and the rhodium complex has been examined by spectroscopic and gel mobility shift assay; condensation of DNA and B-->Z transition have also been described. Arene ruthenium(II) and EPh3 (E = P, As)-containing arene ruthenium(II) complexes exhibited strong binding behavior, however, rhodium(III) complexes were found to be Topo II inhibitors with an inhibition percentage of 70% (7) and 30% (7a). Furthermore, arene ruthenium complexes containing polypyridyl ligands also act as mild Topo II inhibitors (10%, 3c and 40%, 3d) in contrast to their precursor complexes. Complexes 4-6 also show significant inhibition of beta-hematin/hemozoin formation activity.     

1,3-diaryltriazenido complexes of ruthenium(I), (II) and (III), and of osmium(III), rhodium(III) and iridium(III)

The synthesis and characterization of the platinum metal—1,3-diaryltriazenido complexes [Ru(ArNNNAr)(CO)₃]₂, [Ru(ArNNNAr)₂]₂, cis-Ru(ArNNNAr)₂(CO)₂, MX₂(ArNNNAr)(PPh₃)₂ (M = Ru, Os; X = Cl, Br) and M′(ArNNNAr)₃ (M′= Ru, Os, Rh and Ir) are reported. Axial ligand substitution in [Ru(ArNNNAr)(CO)₃]₂ and adduct formation by [Ru(ArNNNAr)₂]₂ are described. In contrast to other known Ru(II)/Ru(II) “lantern” molecules, the species [Ru(ArNNNAr)₂]₂ have measured magnetic moments equivalent to ca one unpaired electron per dimer, which are presumably due to population of the spin states σ²π⁴δ²π^*4 and σ²π⁴δ²π^*3σ^*1.