The Influence of N‐Heterocyclic Carbenes (NHC) on the Reactivity of [Ru(NHC)4H]+ With H2, N2, CO and O2

The five‐coordinate ruthenium N‐heterocyclic carbene (NHC) hydrido complexes [Ru(IiPr₂Me₂)₄H][BAr^F₄] ( 1 ; IiPr₂Me₂=1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene; Ar^F=3,5‐(CF₃)₂C₆H₃), [Ru(IEt₂Me₂)₄H][BAr^F₄] ( 2 ; IEt₂Me₂=1,3‐diethyl‐4,5‐dimethylimidazol‐2‐ylidene) and [Ru(IMe₄)₄H][BAr^F₄] ( 3 ; IMe₄=1,3,4,5‐tetramethylimidazol‐2‐ylidene) have been synthesised following reaction of [Ru(PPh₃)₃HCl] with 4–8 equivalents of the free carbenes at ambient temperature. Complexes 1 – 3 have been structurally characterised and show square pyramidal geometries with apical hydride ligands. In both dichloromethane or pyridine solution, 1 and 2 display very low frequency hydride signals at about δ ?41. The tetramethyl carbene complex 3 exhibits a similar chemical shift in toluene, but shows a higher frequency signal in acetonitrile arising from the solvent adduct [Ru(IMe₄)₄(MeCN)H][BAr^F₄], 4 . The reactivity of 1 – 3 towards H₂ and N₂ depends on the size of the N‐substituent of the NHC ligand. Thus, 1 is unreactive towards both gases, 2 reacts with both H₂ and N₂ only at low temperature and incompletely, while 3 affords [Ru(IMe₄)₄(η²‐H₂)H][BAr^F₄] ( 7 ) and [Ru(IMe₄)₄(N₂)H][BAr^F₄] ( 8 ) in quantitative yield at room temperature. CO shows no selectivity, reacting with 1 – 3 to give [Ru(NHC)₄(CO)H][BAr^F₄] ( 9 – 11 ). Addition of O₂ to solutions of 2 and 3 leads to rapid oxidation, from which the Ru^III species [Ru(NHC)₄(OH)₂][BAr^F₄] and the Ru^IV oxo chlorido complex [Ru(IEt₂Me₂)₄(O)Cl][BAr^F₄] were isolated. DFT calculations reproduce the greater ability of 3 to bind small molecules and show relative binding strengths that follow the trend CO ? O₂ > N₂ > H₂.     

Near‐IR Absorbing Ruthenium Complexes of Non‐Innocent 6,12‐Di(pyridin‐2‐yl)indolo[3,2‐b]carbazole: Variation as a Function of Co‐Ligands

This article deals with the hitherto unexplored metal complexes of deprotonated 6,12‐di(pyridin‐2‐yl)‐5,11‐dihydroindolo[3,2‐b]carbazole (H₂L). The synthesis and structural, optical, electrochemical characterization of dimeric [{Ru^III(acac)₂}₂(μ‐L^.?)]ClO₄ ([ 1 ]ClO₄, S=1/2), [{Ru^II(bpy)₂}₂(μ‐L^.?)](ClO₄)₃ ([ 2 ](ClO₄)₃, S=1/2), [{Ru^II(pap)₂}₂(μ‐L^2?)](ClO₄)₂ ([ 4 ](ClO₄)₂, S=0), and monomeric [(bpy)₂Ru^II(HL^?)]ClO₄ ([ 3 ]ClO₄, S=0), [(pap)₂Ru^II(HL^?)]ClO₄ ([ 5 ]ClO₄, S=0) (acac=σ‐donating acetylacetonate, bpy=moderately π‐accepting 2,2’‐bipyridine, pap=strongly π‐accepting 2‐phenylazopyridine) are reported. The radical and dianionic states of deprotonated L in isolated dimeric 1 ⁺/ 2 ³⁺ and 4 ²⁺, respectively, could be attributed to the varying electronic features of the ancillary (acac, bpy, and pap) ligands, as was reflected in their redox potentials. Perturbation of the energy level of the deprotonated L or HL upon coordination with {Ru(acac)₂}, {Ru(bpy)₂}, or {Ru(pap)₂} led to the smaller energy gap in the frontier molecular orbitals (FMO), resulting in bathochromically shifted NIR absorption bands (800–2000 nm) in the accessible redox states of the complexes, which varied to some extent as a function of the ancillary ligands. Spectroelectrochemical (UV/Vis/NIR, EPR) studies along with DFT/TD‐DFT calculations revealed (i) involvement of deprotonated L or HL in the oxidation processes owing to its redox non‐innocent potential and (ii) metal (Ru^III/Ru^II) or bpy/pap dominated reduction processes in 1 ⁺ or 2 ²⁺/ 3 ⁺/ 4 ²⁺/ 5 ⁺, respectively.     

Steric effects on the electronic and molecular structures of nickel(II) and cobalt(II) 2,6-dipyrazol-1-ylpyridine complexes

The complexes [M(L¹R)₂](BF₄)₂ (M=Ni, Co; L¹R=2,6-dipyrazol-1-ylpyridine [L¹H], 2,6-bis-{3-iso-propylpyrazol-1-yl}pyridine [L¹Prⁱ], 2,6-bis-{3-phenylpyrazol-1-yl}pyridine [L¹Ph], 2,6-bis-{3-[2,4,6-trimethylphenyl]pyrazol-1-yl}pyridine [L¹Mes]) and [M(L²)₂](BF₄)₂ (M=Ni, Co; L²=2-{3-[2,4,6-trimethylphenyl]pyrazol-1-yl}-6-{5-[2,4,6-trimethylphenyl]pyrazol-1-yl}pyridine) have been prepared. Single crystal structure determinations of [M(L¹H)₂](BF₄)₂ (M=Ni, Co) and solvates of [Ni(L¹Mes)₂](BF₄)₂, [Co(L¹Mes)₂](ClO₄)₂ and [Co(L²)₂](BF₄)₂ all show six-coordinate metal centres with local near-D_2d symmetry. The L¹Mes and L² mesityl substituents have only a small effect on the MN{pyrazole} (M=Ni, Co) bond lengths in these compounds. The d–d spectra of the complexes show that L¹Mes is a significantly better donor ligand than L¹H, L¹Prⁱ or L¹Ph, and that L¹Prⁱ is a weaker ligand than might be expected purely on inductive grounds. A combination of UV–Vis/NIR, EPR, NMR and magnetic measurements have demonstrated that all the Co(II) compounds are high-spin in the solid state and in solution at 290 K.     

Ruthenafuran Complexes Supported by the Bipyridine-Bis(diphenylphosphino)methane Ligand Set: Synthesis and Cytotoxicity Studies

Mononuclear and dinuclear Ru(II) complexes cis-[Ru(κ²-dppm)(bpy)Cl₂] (1), cis-[Ru(κ²-dppe)(bpy)Cl₂] (2) and [Ru₂(bpy)₂(μ-dpam)₂(μ-Cl)₂](Cl)₂ ([3](Cl)₂) were prepared from the reactions between cis(Cl), cis(S)-[Ru(bpy)(dmso-S)₂Cl₂] and diphosphine/diarsine ligands (bpy = 2,2′-bipyridine; dppm = 1,1-bis(diphenylphosphino)methane; dppe = 1,2-bis(diphenylphosphino)ethane; dpam = 1,1-bis(diphenylarsino)methane). While methoxy-substituted ruthenafuran [Ru(bpy)(κ²-dppe)(C^O)]⁺ ([7]⁺; C^O = anionic bidentate [C(OMe)CHC(Ph)O]⁻ chelate) was obtained as the only product in the reaction between 2 and phenyl ynone HC≡C(C=O)Ph in MeOH, replacing 2 with 1 led to the formation of both methoxy-substituted ruthenafuran [Ru(bpy)(κ²-dppm)(C^O)]⁺ ([4]⁺) and phosphonium-ring-fused bicyclic ruthenafuran [Ru(bpy)(P^C^O)Cl]⁺ ([5]⁺; P^C^O = neutral tridentate [(Ph)₂PCH₂P(Ph)₂CCHC(Ph)O] chelate). All of these aforementioned metallafuran complexes were derived from Ru(II)–vinylidene intermediates. The potential applications of these metallafuran complexes as anticancer agents were evaluated by in vitro cytotoxicity studies against cervical carcinoma (HeLa) cancer cell line. All the ruthenafuran complexes were found to be one order of magnitude more cytotoxic than cisplatin, which is one of the metal-based anticancer agents being widely used currently.     

Electrochemical studies on neutral triple-bridged di-ruthenium compounds.

Voltammetric studies reveal that, like [Ru₂Cl₄(PPh₃)₄(CO)], triply-bridged complexes [Ru₂Cl₄L₅] (L = PClPh₂, PMePh₂, PEt₂Ph) are reversibly oxidized to [Ru₂Cl₄L₅]⁺. The mixed valence complexes [Ru₂Cl₅L₃Y] (L = PPh₃, P(tol)₃; Y = CO, CS) undergo a corresponding reduction to [Ru₂Cl₅L₃Y]^?; whereas [Ru₂Cl₅L₄] (L = PEt₂Ph, As(tol)₃) and [Ru₂Cl₆(AsPh₃)₃] are both reduced $\text{and}$ oxidised in reversible one-electron steps. For the bridging (RuCl₃Ru)^z+ moiety, the redox series z = 1, 2, 3, 4 is established.     

Electron-Rich Diruthenium Complexes with π-Extended Alkenyl Ligands and Their F4TCNQ Charge-Transfer Salts**

The synthesis of dinuclear ruthenium alkenyl complexes with {Ru(CO)(PⁱPr₃)₂(L)} entities (L=Cl⁻ in complexes Ru₂-3 and Ru₂-7 ; L=acetylacetonate (acac⁻) in complexes Ru₂-4 and Ru₂-8 ) and with π-conjugated 2,7-divinylphenanthrenediyl ( Ru₂-3 , Ru₂-4 ) or 5,8-divinylquinoxalinediyl ( Ru₂-7 , Ru₂-8 ) as bridging ligands are reported. The bridging ligands are laterally π-extended by anellating a pyrene ( Ru₂-7 , Ru₂-8 ) or a 6,7-benzoquinoxaline ( Ru₂-3 , Ru₂-4 ) π-perimeter. This was done with the hope that the open π-faces of the electron-rich complexes will foster association with planar electron acceptors via π-stacking. The dinuclear complexes were subjected to cyclic and square-wave voltammetry and were characterized in all accessible redox states by IR, UV/Vis/NIR and, where applicable, by EPR spectroscopy. These studies signified the one-electron oxidized forms of divinylphenylene-bridged complexes Ru₂-7 , Ru₂-8 as intrinsically delocalized mixed-valent species, and those of complexes Ru₂-3 and Ru₂-4 with the longer divinylphenanthrenediyl linker as partially localized on the IR, yet delocalized on the EPR timescale. The more electron-rich acac⁻ congeners formed non-conductive 1 : 1 charge-transfer (CT) salts on treatment with the F₄TCNQ electron acceptor. All spectroscopic techniques confirmed the presence of pairs of complex radical cations and F₄TCNQ^.− radical anions in these CT salts, but produced no firm evidence for the relevance of π-stacking to their formation and properties.     

Mixed-Valence 24-Vanadophosphate Decorated with Six RuII(dmso)3 Groups: [{RuII3(dmso)9PVV11VIVRuIIIO37(OH)3}2]8?

The mixed-valence 24-vanadophosphate (1) has been synthesized and characterized in the solid state by IR, magnetism, EPR, XPS, and elemental analysis. Single-crystal X-ray analysis was carried out on (Na-1), which crystallizes in the triclinic system, space group , with a = 17.168(3) ?, b = 18.1971(14) ?, c = 20.1422(13) ?, α = 114.753(3)°, β = 99.390(4)°, γ = 95.124(4)°, and Z = 2. Polyanion 1 has an unusual, open structure composed of 2 Ru^IIIO₆ octahedra, 2 V^IVO₆ octahedra, 14 V^VO₅ square-pyramids, 8 V^VO₄ tetrahedra, and 2 PO₄ tetrahedra which are all directly linked via edges and corners. The outer surface of 1 is decorated with six Ru^II(dmso)₃ groups. XPS studies on Na-1 confirm the presence of 2 Ru^III and 6 Ru^II as well as 22 V^V and 2 V^IV centers. Magnetic susceptibility data on Na-1 show that the V^IV–Ru^III pairs are coupled antiferromagnetically, with J ₁ = −13 K and J ₂ ∼ −3 K. We did not detect any peak in our EPR measurements on Na-1, thus supporting the conclusion that Na-1 is diamagnetic in its ground state. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. In Memoriam Prof. F. A. Cotton     

A SIMPLE ROUTE FOR SYNTHESES OF TRIHALIDE-BRIDGED CARBONYL DIRUTHENIUM(II,III) COMPLEXES: CRYSTAL AND MOLECULAR STRUCTURE OF ttt-[RuIICl2(CO)2(PPh3)2],[(CO)(AsPh3)2RuII(μ-Cl3)RuIIICl2(AsPh3)] AND ([CO)(PPh3)2RuII(μ-Br3)RuIIIBr2(PPh3)], SPECTROSCOPIES,ELECTROCHEMISTRY AND PROPERTIES

Abstract

The triply halide-bridged binuclear complexes [Ru₂Cl₅(CO)(AsPh₃)₃] (AsPh₃ = triphenylarsine), [Ru₂Cl₅(CO)(PPh₃)₂(AsPh₃)] (PPh₃ = triphenylphosphine), [Ru₂Cl₅(CO)(AsPh₃)₂(PPh₃)], [Ru₂ Br₅(CO)(PPh₃)₃], [Ru₂Cl₅(CO)(P{p-tol}₃)₂(PPh₃)] (P{p-tol}₃ = tri-p-tolylphosphine) and [Ru₂ Br₂Cl₃(PPh₃)₂(AsPh₃)] were prepared from the precursor compounds ttt-[RuX₂(CO)₂(P)₂] (X = Cl or Br) and [RuY₃(P')₂S]·S (Y = Cl or Br; P=PPh₃, AsPh₃ or P{p- tol}₃ and P' = AsPh₃ or PPh₃; S=DMA or MeOH, where DMA = N,N'-dimethylacetamide). The molecular structures of the binuclear complexes [Ru₂Cl₅(CO)(AsPh₃)₃] (P2_1/c), [Ru₂Br₅(CO)(PPh₃)₃] (P2_1/c) and ttt-[RuCl₂(CO)₂(PPh₃)₂] (P1) were determined by X-ray diffraction methods. The complexes are always formed by two Ru atoms bridged through three halide anions, two of which are × type (from the Ru^II precursor) and the other is Y type (from the ruthenium^III precursor) confirming our previously suggested mechanism for obtaining this class of complexes. The Ru^II atom is also coordinated to a carbon monoxide molecule and two P ligands from the ttt-starting isomer whereas the Ru^III atom is bonded to two non-bridging Y halides and one P' molecule. The presence of Ru^III was confirmed by EPR data, a technique that was also useful to suggest the symmetry of the complexes. The absence of intervalence charge-transfer transitions (IT) in the near infrared spectrum confirms that the binuclear complexes have localized valence. The IR spectra of the complexes show; (CO) bands close to 1970 cm^?1 and ν(Ru-Cl) or(Ru-Br) bands at about 230–380 cm^?1 corresponding to halides at terminal or bridged positions. Two widely separated redox processes, Ru^II/Ru^II←Ru^II/Ru^III→Ru^III/Ru^III, were observed by cyclic voltammetry and differential pulse voltammetry.     

Synthesis,Characterization, and X‐ray Structures of Ru3(CO)9(dotpm)(L) Complexes [L = PPh3, P(C6H4Cl‐p)3, and PPh2(C6H4Br‐p)]

The reaction of Ru₃(CO)₁₀(dotpm) ( 1 ) [dotpm = (bis(di‐ortho‐tolylphosphanyl)methane)] and one equivalent of L [L = PPh₃, P(C₆H₄Cl‐p)₃ and PPh₂(C₆H₄Br‐p)] in refluxing n‐hexane afforded a series of derivatives [Ru₃(CO)₉(dotpm)L] ( 2 – 4 ), respectively, in ca. 67–70 % yield. Complexes 2 – 4 were characterized by elemental analysis (CHN), IR, ¹H NMR, ¹³C{¹H} NMR and ³¹P{¹H} NMR spectroscopy. The molecular structures of 2 , 3 , and 4 were established by single‐crystal X‐ray diffraction. The bidentate dotpm and monodentate phosphine ligands occupy equatorial positions with respect to the Ru triangle. The effect of substitution resulted in significant differences in the Ru–Ru and Ru–P bond lengths.     

Reactivity of TpRu(L)(NCMe)R (L = CO, PMe3; R = Me, Ph) systems with isonitriles: Experimental and computational studies toward the intra- and intermolecular hydroarylation of isonitriles

The Ru(II) phenyl complex TpRu(PMe₃)(NCMe)Ph {Tp = hydridotris(pyrazolyl)borate} reacts with isonitriles to form complexes of the type TpRu(PMe₃)(CNR)Ph (R = ^tBu, CH₂Ph, CH₂CH₂Ph). Neither thermal nor photolytic reactions of these systems with excess isonitrile and benzene resulted in the production of corresponding imines. DFT studies that probed the energetics of the desired catalytic transformations revealed that (Tab)Ru(PH₃)(CNCH₂CH₂Ph)Ph {Tab = tris(azo)borate} is the most stable species in a proposed catalytic cycle. Exclusive of calculated transition states, the highest points on the calculated free energy surface are 34 kcal/mol, for (Tab)Ru(PH₃)(o,η²-C,C-CNCH₂CH₂Ph)Ph {relative to the starting material (Tab)Ru(PH₃)(CNCH₂CH₂Ph)Ph}, and 27 kcal/mol for the C-H activation product (Tab)Ru(PH₃)(o-C₆H₄CH₂CH₂NC) and benzene. The substantial increases in free energy result primarily from the loss of the stable ruthenium-η¹-isonitrile interaction.     

Nucleophilic Aromatic Addition Reactions of the Metallabenzenes and Metallapyridinium: Attacking Aromatic Metallacycles with Bis(diphenylphosphino)methane to Form Metallacyclohexadienes and Cyclic η2‐Allene‐Coordinated Complexes

The reactions of phosphonium‐substituted metallabenzenes and metallapyridinium with bis(diphenylphosphino)methane (DPPM) were investigated. Treatment of [Os{CHC(PPh₃)CHC(PPh₃)CH}Cl₂(PPh₃)₂]Cl with DPPM produced osmabenzenes [Os{CHC(PPh₃)CHC(PPh₃)CH}Cl₂{(PPh₂)CH₂(PPh₂)}]Cl ( 2 ), [Os{CHC(PPh₃)CHC(PPh₃)CH}Cl{(PPh₂)CH₂(PPh₂)}₂]Cl₂ ( 3 ), and cyclic osmium η²‐allene complex [Os{CH?C(PPh₃)CH?(η²‐C?CH)}Cl₂{(PPh₂)CH₂(PPh₂)}₂]Cl ( 4 ). When the analogue complex of osmabenzene 1 , ruthenabenzene [Ru{CHC(PPh₃)CHC(PPh₃)CH}Cl₂(PPh₃)₂]Cl, was used, the reaction produced ruthenacyclohexadiene [Ru{CH?C(PPh₃)CH?C(PPh₃)CH}Cl{(PPh₂)CH₂(PPh₂)}₂]Cl₂ ( 6 ), which could be viewed as a Jackson–Meisenheimer complex. Complex 6 is unstable in solution and can easily be convert to the cyclic ruthenium η²‐allene complexes [Ru{CH?C(PPh₃)CH?(η²‐C?CH)}Cl{(PPh₂)CH₂(PPh₂)}₂]Cl₂ ( 7 ) and [Ru{CH?C(PPh₃)CH?(η²‐C?CH)}Cl₂{(PPh₂)CH₂(PPh₂)}₂]Cl ( 8 ). The key intermediates of the reactions have been isolated and fully characterized, further supporting the proposed mechanism for the reactions. Similar reactions also occurred in phosphonium‐substituted metallapyridinium [OsCl₂{NHC(CH₃)C(Ph)C(PPh₃)CH}(PPh₃)₂]BF₄ to give the cyclic osmium η²‐allene‐imine complex [OsCl₂{NH?C(CH₃)C(Ph)?(η²‐C?CH)}{(PPh₂)CH₂(PPh₂)}(PPh₃)]BF₄ ( 11 ).     

Dioxygen Activation by Redox-Active Bis(aldimine) Ligand Bridged Diruthenium Complex Possessing Singlet Ground State

The unexplored ‘actor’ behavior of redox-active bis(aldimine) congener, p-phenylene-bis(picoline)aldimine (L1), towards dioxygen activation and subsequent functionalization of its backbone was demonstrated on coordination with {Ru(acac)₂} (acac= acetylacetonate). Reaction under aerobic condition led to the one-pot generation of dinuclear complexes with unperturbed L1, imino-carboxamido (L2⁻), and bis(carboxamido) (L3²⁻)-bridged isovalent {Ru^II(μ-L1)Ru^II}, 1/ {Ru^III(μ-L3²⁻)Ru^III}, 3 and mixed-valent {Ru^II(μ-L2⁻)Ru^III}, 2 . Authentication of the complexes along with the redox non-innocence behavior of their bridge have been validated through structure, spectroelectrochemistry and DFT calculations. Kinetic and isotope labelling experiments together with DFT analyzed transition states justified the consideration of redox shuttling at metal/L1 interface for ³O₂ activation despite of the closed shell configuration of 1 (S=0) to give carboxamido derived 2 / 3 .     

trans‐Di­chloro­tetrakis(4‐methylpyrimidine‐N1)­ruthenium(II)

The title compound, trans‐[Ru^IICl₂(N¹‐mepym)₄] (mepym is 4‐methylpyrimidine, C₅H₆N₂), obtained from the reaction of trans,cis,cis‐[Ru^IICl₂(N¹‐mepym)₂(SbPh₃)₂] (Ph is phenyl) with excess mepym in ethanol, has fourfold crystallographic symmetry and has the four pyrimidine bases coordinated through N¹ and arranged in a propeller‐like orientation. The Ru—N and Ru—Cl bond distances are 2.082 (2) and 2.400 (4) Å, respectively. The methyl group, and the N³ and Cl atoms are involved in intermolecular C—H?N and C—­H?Cl hydrogen‐bond interactions.     

The role of the heteroatom (X?=?SiIV, PV, and SVI) on the reactivity of {��-[(H2O)RuIII(��-OH)2RuIII(H2O)][X n+W10O36]}(8?n)? with the O2 molecule

The mechanism of reaction of the di-Ru-substituted polyoxometalate, {??-[(H₂O)Ru^III(??-OH)₂Ru^III(H₂O)][X ⁿ⁺W₁₀O₃₆]}^(8?n)?, I_X, with O₂, i.e. I_X?+?O₂????{??-[(^·O)Ru^IV(??-OH)₂Ru^IV(O^·)][X ⁿ⁺W₁₀O₃₆]}^(8?n)??+?2H₂O, (1), was studied at the B3LYP density functional and self-consistent reaction field IEF-PCM (in aqueous solution) levels of theory. The effect of the nature of heteroatom X (where X?=?Si, P and, S) on the calculated energies and mechanism of the reaction (1) was elucidated. It was shown that the nature of X only slightly affects the reactivity of I_X with O₂, which is a 4-electron oxidation process. The overall reaction (1): (a) proceeds with moderate energy barriers for all studied X??s [the calculated rate-determining barriers are X?=?Si (18.7?kcal/mol)?<?S (20.6?kcal/mol)?<?P (27.2?kcal/mol) in water, and X?=?S (18.7?kcal/mol)?<?P (21.4?kcal/mol)?<?Si (23.1?kcal/mol) in the gas phase] and (b) is exothermic [by X?=?Si [28.7 (22.1) kcal/mol]?>?P [21.4 (9.8) kcal/mol]?>?S [12.3 (5.0) kcal/mol]. The resulting $ \left\{ {\gamma - \left[ {\left( {^{ \cdot } {\text{O}}} \right) {\text{Ru}}^{\text{IV}} \left( {\mu - {\text{OH}}} \right)_{2} {\text{Ru}}^{\text{IV}} \left( {{\text{O}}^{ \cdot } } \right)} \right]\left[ {{\text{X}}^{{{\text{n}} + }} {\text{W}}_{10} {\text{O}}_{36} } \right]} \right\}^{{\left( {8 - {\text{n}}} \right) - }} $ , VI_X, complex was found to have two Ru^IV?=?O^· units, rather than Ru^V?=?O units. The ??reverse?? reaction, i.e., water oxidation by VI_X is an endothermic process and unlikely to occur for X?=?Si and P, while it could occur for X?=?S under specific conditions. The lack of reactivity of VI_X biradical toward the water molecule leads to the formation of the stable [{Ru ₄ ^IV O₄(OH)₂(H₂O)₄}[(??-XW₁₀O₃₆]₂}^m? dimer. This conclusion is consistent with our experimental findings; previously we prepared the $ \left[ {\left\{ {{\text{Ru}}_{4}^{\text{IV}} {\text{O}}_{4} ({\text{OH}})_{2} \left( {{\text{H}}_{ 2} {\text{O}}} \right)_{4} } \right\}} \right[\left( {\gamma - {\text{XW}}_{10} {\text{O}}_{36} } \right]_{2} \}^{{{\text{m}} - }} $ dimers for X?=?Si (m?=?10) [Geletii et al. in Angew Chem Int Ed 47:3896?C3899, 2008 and J Am Chem Soc 131:17360?C17370, 2009] and P (m?=?8) [Besson et al. in Chem Comm 46:2784?C2786, 2010] and showed them to be very stable and efficient catalysts for the oxidation of water to O₂.     

Mg2Ru2Cl10O·16H2O

Mg₂Ru₂Cl₁₀O·16H₂O {dimagnesium μ‐oxo‐bis­[penta­chloro­ruthenate(IV)] hexa­deca­hydrate} crystallizes in the monoclinic system (space group P2₁/c). The structure consists of layers of [Ru₂Cl₁₀O]⁴⁻ anions, [Mg(H₂O)₆]²⁺ cations and water mol­ecules stacked along the a axis. Only the O atom bonded to Ru occupies the 2a site with symmetry. All the other atoms occupy general 4e sites. The crystal structure is stabilized by O—H⋯O and O—H⋯Cl inter­actions.     

Electronically Strongly Coupled Divinylheterocyclic‐Bridged Diruthenium Complexes

Complexes [{Ru(CO)Cl(PiPr₃)₂}₂(μ‐2,5‐(CH?CH)₂‐^cC₄H₂E] (E=NR; R=C₆H₄‐4‐NMe₂ ( 10 a ), C₆H₄‐4‐OMe ( 10 b ), C₆H₄‐4‐Me ( 10 c ), C₆H₅ ( 10 d ), C₆H₄‐4‐CO₂Et ( 10 e ), C₆H₄‐4‐NO₂ ( 10 f ), C₆H₃‐3,5‐(CF₃)₂ ( 10 g ), CH₃ ( 11 ); E=O ( 12 ), S ( 13 )) are discussed. The solid state structures of four alkynes and two complexes are reported. (Spectro)electrochemical studies show a moderate influence of the nature of the heteroatom and the electron‐donating or ‐withdrawing substituents R in 10 a – g on the electrochemical and spectroscopic properties. The CVs display two consecutive one‐electron redox events with ΔE°′=350–495 mV. A linear relationship between ΔE°′ and the σ_p Hammett constant for 10 a–f was found. IR, UV/Vis/NIR and EPR studies for 10 ⁺– 13 ⁺ confirm full charge delocalization over the {Ru}CH?CH‐heterocycle‐CH?CH{Ru} backbone, classifying them as Class III systems according to the Robin and Day classification. DFT‐optimized structures of the neutral complexes agree well with the experimental ones and provide insight into the structural consequences of stepwise oxidations.     

Electrochemical behaviour of [Ru(L)(CO)2Cl2] [Ru(L)(CO)Cl3][Me4N] and [Ru(L)(CO)2(CH3CN)2][CF3SO3]2 complexes (L = 2,2′- bipyridine or 4,4′-isopropoxycarbonyl-2,2′-bipyridine)

The clectrochemical behaviour of the complexes [Ru^II(L)(CO)₂Cl₂], [Ru^II(L)(CO)Cl₃][Me₄N] and [Ru^II(L)(CO)₂(CH₃CN)₂][CF₃SO₃]₂ (L = 2,2′-bipyridine or 4,4′-isopropoxycarbonyl-2,2′-bipyridine) has been investigated in CH₃CN. The oxidation of [Ru(L)(CO)₂Cl₂] produces new complexes [Ru^III(L)(CO)(CH₃CN)₂Cl]²⁺ as a consequence of the instability of the electrogenerated transient Ru^III species [Ru^III(L)(CO)₂Cl₂]⁺. In contrast, the oxidation of [Ru^II(L)(CO)Cl₃][Me₄N] produces the stable [Ru^III(L)(CO)Cl₃] complex. In contrast [Ru^II(L)(CO)₂(CH₃CN)₂][CF₃SO₃]₂ is not oxidized in the range up to the most positive potentials achievable. The reduction of [Ru^II(L)(CO)₂Cl₂] and [Ru^II(L)(CO)₂(CH₃CN)₂][CF₃SO₃]₂ results in the formation of identical dark blue strongly adherent electroactive films. These films exhibit the characteristics of a metal-metal bond dimer structure. No films are obtained on reduction of [Ru^II(L)(CO)Cl₃][Me₄N]. The effect of the substitution of the bipyridine ligand by electron-withdrawing carboxy ester groups on the electrochemical behaviour of all these complexes has also been investigated.     

Ruthenium and rhodium nitrosyl complexes containing dichalcogenoimidodiphosphinate ligands

Interaction of [Ru(NO)Cl₃(PPh₃)₂] with K[N(R₂PS)₂] in refluxing N,N-dimethylformamide afforded trans-[Ru(NO)Cl{N(R₂PS)₂}₂] (R = Ph (1), Prⁱ (2)). Reaction of [Ru(NO)Cl₃(PPh₃)₂] with K[N(Ph₂PSe)₂] led to formation of a mixture of trans-[Ru(NO)Cl{N(Ph₂PSe)₂}₂] (3) and trans-[Ru(NO)Cl{N(Ph₂PSe)₂}{Ph₂P(Se)NPPh₂}] (4). Reaction of Ru(NO)Cl₃ · xH₂O with K[N(Ph₂PO)₂] afforded cis-[Ru(NO)(Cl){N(Ph₂PO)₂}₂] (5). Treatment of [Rh(NO)Cl₂(PPh₃)₂] with K[N(R₂PQ)₂] gave Rh(NO){N(R₂PQ)₂}₂] (R = Ph, Q = S (6) or Se (7); R = Prⁱ, Q = S (8) or Se (9)). Protonation of 8 with HBF₄ led to formation of trans-[Rh(NO)Cl{HN(Prⁱ₂PS)₂}₂][BF₄]₂ (10). X-ray diffraction studies revealed that the nitrosyl ligands in 2 and 4 are linear, whereas that in 9 is bent with the Rh–N–O bond angle of 125.7(3)°.     

Layer-by-layer assembly of Ru3+ and $$ {\text{Si}}_{{\text{8}}} {\text{O}}^{{8 - }}_{{20}} $$ into electrochemically active silicate films

A porous silicate is obtained from octa-anionic cage-like poly-silicate (PS) and Ru³⁺ cations in an ethanol-based layer-by-layer assembly process. Electrochemical experiments (voltammetry and impedance spectroscopy) confirm the formation of redox-active ruthenium centers in the form of hydrous ruthenium oxide throughout the film deposit. Oxidation of Ru(III) to Ru(IV) at a potential below 0.5 V vs saturated Calomel electrode (SCE) is reversible, but a potential positive of 0.5 V vs SCE is associated with an irreversible change in reactivity, which is characteristic for very small hydrous ruthenium oxide nanoparticles. Further voltammetric experiments are performed in aqueous phosphate buffer solutions, and the effects of number of layers, scan rate, and pH are investigated. Three aqueous redox systems are studied in contact with the PS–Ru³⁺ films. The reduction of cationic methylene blue adsorbed onto the negative surface of the nanocomposite silicate is shown to occur, although most of the bound methylene blue appears to be electrochemically inactive either bound to silicate or buried into small pores. The PS–Ru³⁺-catalyzed oxidations of hydroquinone and arsenite(III) are investigated. Scanning electron microscopy images show that a macroscopically uniform porous surface is formed after deposition of 50 layers of the PS–Ru³⁺ nanocomposite. However, atomic force microscopy images demonstrate that in the initial deposition stages, irregular island growth occurs. The average rate of thickness increase for PS–Ru³⁺ nanocomposite films is 6 nm per deposition cycle.     

Synthesis and spectral studies of diorganotin(IV) dialkyldithiophosphates

Two series of diorganotin(IV) dialkyldithiophosphates, [RR′Sn{SSP(OR″)₂}₂](R = Me or Et; R′= Ph; R″ = Et, Prⁿ, Prⁱ or Buⁿ) and [RR′Sn(Cl){SSP(OR″)₂}] (R = R′= Me, Et or Ph; R″ = Ph; R″ = Et, Prⁱ or Buⁿ) were prepared and characterised by i.r. and NMR (¹H, ¹³C, ³¹P, ¹⁹⁹Sn) spectroscopy. The NMR data indicate five and six coordinate geometries for [RR′Sn(Cl){SSP(OR″)₂}] and [RR′Sn{SSP(OR″)₂}₂] complexes, respectively. The chloro complexes showed ²J (PSn) whereas such couplings were not observed in the spectra of [RR′Sn{SSP(OR″)₂}₂].