Synthesis and structural characterisation of a ruthenium dinitrosyl complex with atrans-chelating bidentate diphosphine (1,10-bis(diphenylphosphinomethyl) [a] benzophenanthrene) chlorodi(nitrosyl)ruthenium tetrafluoroborate, [RuCl(NO)2{(Ph2PCH2)2-C18H10}]BF4

Summary [RuCl(NO)₂(dppbp)]BF₄ (dppbp=(Ph₂PCH₂)_2–) has been synthesised from [RuCl(NO)₂(PPh₃)₂]BF₄ and dppbp and characterised in the solid state by a single crystal x-ray determination. The [RuCl(NO)₂(dppbp)]⁺ cation, has an approximately square-pyramidal co-ordination geometry with the dppbp ligand occupyingtrans-basal sites. The nitrosyl ligand in the apical site is partially bent [Ru–N–O=156.2(7)⁰] and the nitrosyl ligand in the basal side is essentially linear [Ru–N–O=172.5(6)⁰]. The¹Hn.m.r. spectrum of [RuCl(NO)₂(dppbp)]BF₄ in solution has provided some insight into the dynamics of the complex in solution.     

Heterodinuclear Ruthenium(II) Complexes of the Bridging Ligand 1,6,7,12‐Tetraazaperylene with Iron(II), Cobalt(II), Nickel(II), as well as Palladium(II) and Platinum(II)

The first heterodinuclear ruthenium(II) complexes of the 1,6,7,12‐tetraazaperylene (tape) bridging ligand with iron(II), cobalt(II), and nickel(II) were synthesized and characterized. The metal coordination sphere in this complexes is filled by the tetradentate N,N′‐dimethyl‐2,11‐diaza[3.3](2,6)‐pyridinophane (L‐N₄Me₂) ligand, yielding complexes of the general formula [(L‐N₄Me₂)Ru(µ‐tape)M(L‐N₄Me₂)](ClO₄)₂(PF₆)₂ with M = Fe {[ 2 ](ClO₄)₂(PF₆)₂}, Co {[ 3 ](ClO₄)₂(PF₆)₂}, and Ni {[ 4 ](ClO₄)₂(PF₆)₂}. Furthermore, the heterodinuclear tape ruthenium(II) complexes with palladium(II)‐ and platinum(II)‐dichloride [(bpy)₂Ru(μ‐tape)PdCl₂](PF₆)₂ {[ 5 ](PF₆)₂} and [(dmbpy)₂Ru(μ‐tape)PtCl₂](PF₆)₂ {[ 6 ](PF₆)₂}, respectively were also prepared. The molecular structures of the complex cations [ 2 ]⁴⁺ and [ 4 ]⁴⁺ were discussed on the basis of the X‐ray structures of [ 2 ](ClO₄)₄ · MeCN and [ 4 ](ClO₄)₄ · MeCN. The electrochemical behavior and the UV/Vis absorption spectra of the heterodinuclear tape ruthenium(II) complexes were explored and compared with the data of the analogous mono‐ and homodinuclear ruthenium(II) complexes of the tape bridging ligand.     

Voltammetry and electrocatalytic properties of cobalt (1,4,8,12-tetraazacyclopentadecane) in aqueous solution

Summary The spectrochemical, electrochemical and electrocatalytic properties of Co[15]aneN₄ ([15]aneN₄ = 1,4,8,12-tetraazacyclopentadecane) have been investigated. The results show that, in aqueous solution, this compound mainly exists as three species whose axial coordination positions are occupied by water and/or hydroxy ligands; it is marginal whether other substrates such as Cl^– and NO _inf3 ^sup– interact with the central ion in acid-base solutions. The approximate Pourbaix diagram of Co^III/II[15]ane N₄ was determined. There is an electrochemically-induced isomerization between two trans conformational isomers of the Co[15]aneN₄ complexes in acid and netural solutions. The Co[15]aneN₄ complex has electrocatalytic properties for reduction of nitrate and nitrite only in strong alkaline solution.     

NO Release from trans-[Ru(NH3)4L(NO)]3+ Complexes Upon Reduction (L = 1-Methylimidazole or Benzoimidazole)

The synthesis, characterization and reactivity of trans-[Ru(NH₃)₄(L)NO](PF₆)₃(L = benzoimidazole or 1-methylimidazole in trans position to NO) are presented. ¹H-n.m.r. spectroscopy data indicate that the benzoimidazole and 1-methylimidazole ligands are coordinated to Ru^II through carbon and nitrogen, respectively. The nitrosyl stretching frequencies [(NO) > 1900 cm^–1] suggest that the coordinated nitrosyl has substantial NO⁺ character. The complexes undergo a single-electron reduction (E ⁰–0.245 versus NHE), which involves the coordinated nitrosyl. Dissociation of NO in the reduced species is facilitated by the 1-methylimidazole ligand, which is not observed for the benzoimidazole species. The complex with 1-methylimidazole does not suffer hydroxide attack on the NO⁺, at least at pH values lower than 11.     

Complexes of 1-thia-4,7,10-triazacyclododecane ([12]aneN3S): Synthesis,structure and stability constants

The 12-membered macrocyclic ligand 1-thia-4,7,10-triazacyclododecane ([12]aneN₃S) has been synthesised, although upon crystallization from acetonitrile a product in which carbon dioxide had added to one secondary amine in the macrocyclic ring (H[12]aneN₃S–CO₂·H₂O) was isolated and subsequently characterised by X-ray crystallography. The protonation constants for [12]aneN₃S and stability constants with Zn(II), Pb(II), Cd(II) and Cu(II) have been determined either potentiometrically or spectrophotometrically in aqueous solution, and compared with those measured or reported for the ligands 1-oxa-4,7,10-triazacyclododecane ([12]aneN₃O) and 1,4,7,10-tetraazacyclododecane ([12]aneN₄). The magnitudes of the stability constants are consistent with trends observed previously for macrocyclic ligands as secondary amine donors are replaced with oxygen and thioether donors although the stability constant for the [Hg([12]aneN₄)]²⁺ complex has been estimated from an NMR experiment to be at least three orders of magnitude larger than reported previously. Zinc(II), mercury(II), lead(II), copper(II) and nickel(II) complexes of [12]aneN₃S have been isolated and characterised by X-ray crystallography. In the case of copper(II), two complexes [Cu([12]aneN₃S)(H₂O)](ClO₄)₂ and [Cu₂([12]aneN₃S)₂(OH)₂](ClO₄)₂ were isolated, depending on the conditions employed. Molecular mechanics calculations have been employed to investigate the relative metal ion size preferences of the [3333], asym-[2424] and sym-[2424] conformation isomers. The calculations predict that the asym-[2424] conformer is most stable for M–N bond lengths in the range 2.00–2.25 Å whilst for the larger metal ions the [3333] conformer is dominant. The disorder seen in the structure of the [Zn([12]aneN₃S)(NO₃)]⁺ complex is also explained by the calculations.     

Synthesis and Characterization of the Mn(II) Complex of [15]aneN5

The complex Mn[15]aneN₅CIPF₆ has been prepared by the reaction of MnCI₂ [15]aneN₅.3HPF₆, and NaOH in water ([15]aneN₅ is 1,4,7,10,13-pentaazacyclopentadecane). The complex is obtained as a white solid formulated as [Mn(C₁₀H₂₅N₅)Cl](PF₆).3/2H₂O. It is a 2: 1 electrolyte in H₂O and a 1:1 electrolyte in CH₃CN, The complex contains high spin Mn(II), μ_eff = 5.83 B.M., and the EPR spectrum of the polycrystalline solid is indicative of rhombic symmetry at the metal site. The proton NMR relaxation enhancement of aqueous solvent by the complex is 2.3 mM^?1S ^?1 at 24 MHz and 25°C and is indicative of one rapidly exchanging water molecule in the coordination sphere of the solvated complex. The stability constant for the formation of the complex in aqueous solution as measured by potentiometric titration (IogK = 10.7) is four orders of magnitude greater than the comparable linear polyamine. In all, the characterization data are consistent with Mn(lI) strongly bound to a distorted or folded ligand and able to accommodate only one additional ligand.     

Synthesis of nitrosylruthenium complexes containing 2,2':6',2"-terpyridine by reactions of alkoxo complexes with acids

Nitrosylruthenium complexes containing 2,2':6',2"-terpyridine (terpy) have been synthesized and characterized. The three alkoxo complexes trans-(NO, OCH3), cis-(Cl, OCH3)-[RuCl(OCH3)(NO)(terpy)]PF6 ([2]PF6), trans-(NO, OC2H5), cis-(Cl, OC2H5)-[RuCl(OC2H5)(NO)(terpy)]PF6 ([3]PF6), and [RuCl(OC3H7)(NO)(terpy)]PF6 ([4]PF6) were synthesized by reactions of trans-(Cl, Cl), cis-(NO, Cl)-[RuCl2(NO)(terpy)]PF6 ([1]PF6) with NaOCH3 in CH3OH, C2H5OH, and C3H7OH, respectively. Reactions of [3]PF6 with an acid such as hydrochloric acid and trifluoromethansulforic acid afford nitrosyl complexes in which the alkoxo ligand is substituted. The geometrical isomer of [1]PF6, trans-(NO, Cl), cis-(Cl, Cl)-[RuCl2(NO)(terpy)]PF6 ([5]PF6), was obtained by the reaction of [3]PF6 in a hydrochloric acid solution. Reaction of [3]PF6 with trifluoromethansulforic acid in CH3CN gave trans-(NO, Cl), cis-(CH3CN, Cl)-[RuCl(CH3CN)(NO)(terpy)]2+ ([6]2+) under refluxing conditions. The structures of [3]PF6, [4]PF6.CH3CN, [5]CF3SO3, and [6](PF6)2 were determined by X-ray crystallograpy.     

Influence of the Coordination of Donor Solvent Molecules to 1,4,7,10-Tetramethyl-1,4,7,10- tetraazacyclododecanenickel(II) and Analogous Nickel(II) Complexes on Their Steric Factors

Coordination equilibrium constants (K _NiS) of some donor solvent molecules to 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecanenickel(II) ([Ni(Me₄[12]aneN₄)]²⁺) were determined in nitrobenzene (a noncoordinating bulk solvent). The first (K _NiS1) and second stepwise coordination equilibrium constants (K _NiS2) for 1,4,7,10-tetraazacyclododecanenickel(II) ([Ni([12]aneN₄)]²⁺), 1,4,8,11-tetraazac yclotetradecane- nickel(II) ([Ni([14] aneN₄)]²⁺), 1,4,8,11-tetrathiacyclotetra-decanenickel(II) ([Ni([14]aneS₄)]²⁺) were also reinvestigated. The K _NiS values for [Ni(Me₄[12]aneN₄)]²⁺ were compared to those of [Ni([12]aneN₄)]²⁺, (1R,4S, 8R,11S)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecanenickel(II) (R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺), R,R,S,S-[Ni(Me₄[14]aneN₄)]²⁺, [Ni([14]aneN₄)]²⁺, and [Ni([14]aneS₄)]²⁺. Coordination of pyridine (Py), N,N,N′,N′-tetramethylurea (TMU), and N,N-dimethylacetamide (DMA) to [Ni(Me₄[12]aneN₄)]²⁺ was observed, although these donor solvent molecules did not coordinate to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺. The K _NiS values for Py, TMU, and DMA are 7.9, 2.8, and 9.0 dm³⋅mol⁻¹, respectively. Some hydrogen-bonding waters were coordinated to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺, but such waters did not coordinate to [Ni(Me₄[12] aneN₄)]²⁺. Also, the K _NiS2 values were larger than the corresponding K _NiS1 values for [Ni([14]aneS₄)]²⁺. Furthermore, the K _NiS1 values for [Ni([12]aneN₄)]²⁺ were the largest among these nickel(II) complex cations. The K _NiS, K _NiS1, and K _NiS2 values are discussed in terms of properties of the donor solvents and steric strains of these nickel(II) complex cations.     

Formation and isomerisation of theO-sulphito complex of 1,4,7,10,13-penta-azacyclohexadecanecobalt(III)

Summary Dissolved SO₂ reacts rapidly with [Co([16]aneN₅)OH]²⁺ to give [Co([16]aneN₅OSO₂]⁺([16]aneN₅=1,4,7,10, 13-penta-azacyclohexadecane), which on immediate acidification loses SO₂ to give [Co([16]aneN₅)OH₂]³⁺. The O-bonded sulphito complex (_max 526 nm) undergoes a slow linkage isomerisation to give the S-bonded species [Co([16]aneN₅)SO₃]⁺ (_max 466 nm), rather than an internal redox reaction. The S-bonded complex has been isolated and characterised as the perchlorate salt [Co([16]aneN₅) (SO₃H)](ClO₄)₂.     

Chemical Swarming: Depending on Concentration,an Amphiphilic Ruthenium Polypyridyl Complex Induces Cell Death via Two Different Mechanisms

The crystal structure and in vitro cytotoxicity of the amphiphilic ruthenium complex [ 3 ](PF₆)₂ are reported. Complex [ 3 ](PF₆)₂ contains a Ru?S bond that is stable in the dark in cell‐growing medium, but is photosensitive. Upon blue‐light irradiation, complex [ 3 ](PF₆)₂ releases the cholesterol–thioether ligand 2 and an aqua ruthenium complex [ 1 ](PF₆)₂. Although ligand 2 and complex [ 1 ](PF₆)₂ are by themselves not cytotoxic, complex [ 3 ](PF₆)₂ was unexpectedly found to be as cytotoxic as cisplatin in the dark, that is, with micromolar effective concentrations (EC₅₀), against six human cancer cell lines (A375, A431, A549, MCF‐7, MDA‐MB‐231, and U87MG). Blue‐light irradiation (λ=450 nm, 6.3 J cm^?2) had little influence on the cytotoxicity of [ 3 ](PF₆)₂ after 6 h of incubation time, but it increased the cytotoxicity of the complex by a factor 2 after longer (24 h) incubation. Exploring the unexpected biological activity of [ 3 ](PF₆)₂ in the dark elucidated an as‐yet unknown bifaceted mode of action that depended on concentration, and thus, on the aggregation state of the compound. At low concentration, it acts as a monomer, inserts into the membrane, and can deliver [ 1 ]²⁺ inside the cell upon blue‐light activation. At higher concentrations (>3–5 μm ), complex [ 3 ](PF₆)₂ forms supramolecular aggregates that induce non‐apoptotic cell death by permeabilizing cell membranes and extracting lipids and membrane proteins.     

Synthesis of trans-[Re(NO)2-(Ph2PCH2CH2PPh2)2][BF4], a formal dinitrosyl complex of rhenium(-I) and its protic denitrosylation. X-Ray structure of trans-[ReF(NO)-(Ph2PCH2CH2PPh2)2][BF4]

Treatment of a THF solution of trans-[ReCl(N₂)(dppe)₂] (dppe = Ph₂PCH₂CH₂PPh₂) with NO, in the presence of Tl[BF₄], forms trans-[Re(NO)₂(dppe)₂][BF₄], a rare formal 20-electron d⁸-rhenium nitrosyl complex which, by reaction with HX (X = BF₄, Cl or HSO₄), gives trans-[ReF(NO)(dppe)₂][BF₄] (2) (the X-ray structure of which is reported) or trans-[ReX(NO)(dppe)₂]X (3, X = Cl or HSO₄), respectively, as well as nitrous oxide.     

Stereospecific synthesis and redox properties of ruthenium(II) carbonyl complexes bearing a redox-active 1,8-naphthyridine unit

Two stereoisomers of cis-[Ru(bpy)(pynp)(CO)Cl]PF₆ (bpy = 2,2′-bipyridine, pynp = 2-(2-pyridyl)-1,8-naphthyridine) were selectively prepared. The pyridyl rings of the pynp ligand in [Ru(bpy)(pynp)(CO)Cl]⁺ are situated trans and cis, respectively, to the CO ligand. The corresponding CH₃CN complex ([Ru(bpy)(pynp)(CO)(CH₃CN)]²⁺) was also prepared by replacement reactions of the chlorido ligand in CH₃CN. Using these complexes, ligand-centered redox behavior was studied by electrochemical and spectroelectrochemical techniques. The molecular structures of pynp-containing complexes (two stereoisomers of [Ru(bpy)(pynp)(CO)Cl]PF₆ and [Ru(pynp)₂(CO)Cl]PF₆) were determined by X-ray structure analyses.     

Electronic tuning of the PNNP ligand for the asymmetric cyclopropanation of olefins catalysed by [RuCl(PNNP)]+

Cationic ruthenium complexes of the type [RuCl(L)(PNNP)]⁺ (L=OEt₂, OH₂), where PNNP is the CF₃-subsituted PNNP ligand N,N′-bis[o-(bis(4-trifluoromethylphenyl)phosphino)benzylidene]-(1S,2S)-diaminocyclohexane 1b, catalyse the asymmetric cyclopropanation of styrene, α-Me-styrene, and 1-octene with ethyl diazoacetate. These complexes are more active and give higher cis- and enantioselectivities than their analogues containing the unsubstituted ligand 1a. Thus, [RuCl(OEt₂)(1b)]PF₆ cyclopropanates α-Me-styrene with 85% cis selectivity and 86% ee in 94% isolated yield.     

Mononuclear ruthenium(II) complexes bearing the (S,S)-Pr-pybox ligand

The complexes trans-[RuCl₂(L){(S,S)-ⁱPr-pybox}] ((S,S)-ⁱPr-pybox = 2,6-bis[4′-(S)-isopropyloxazolin-2′-yl]pyridine, L = PMe₃ (1), P(OMe)₃ (2), PPh₂(CH₂CHCH₂) (3), CNBn (5), CNCy (6) and MeCN (7)) have been synthesized by substitution of ethylene on the precursor trans-[RuCl₂(η²-C₂H₄){(S,S)-ⁱPr-pybox}]. This complex also reacts with cyclooctadiene (cod) or norbornadiene (nbd) and NaPF₆, in refluxing methanol, giving the coordination compounds [RuCl(η⁴-cod){(S,S)-ⁱPr-pybox}][PF₆] (8) and [RuCl(η⁴-nbd){(S,S)-ⁱPr-pybox}][PF₆] (9). The structures of complexes [RuCl(CO)(PPh₃)(H-pybox)][BF₄] (H-pybox = 2,6-bis(dihydrooxazolin-2′-yl)pyridine) (4), 6 and 8, have been resolved by X-ray diffraction methods. The catalytic activity of the new complexes in transfer hydrogenation of acetophenone has also been examined.     

A structural and n.m.r. investigation of chlorodinitrosyl bis(triphenyl phosphine) osmium(1+) tetrafluoroborate, [OsCl(NO)2(PPh3)2]BF4

Summary [OsCl(NO)₂(PPh₃)₂]BF₄ has been synthesised from [OsCl(CO)(NO)(PPh₃)₂] and NOBF₄ and characterised in the solid state by a single crystal x-ray analysis determination and in solution by³¹P{¹H} and¹⁵N n.m.r. studies. The nitrosyl ligands in [OsCl(NO)₂(PPh₃)₂]⁺ are approximately linear, and 170(1)⁰, and the co-ordination geometry about the metal ion is close to trigonal bipyramidal. This contrasts with the occurrence of a linear and a bent nitrosyl ligand in [RuCl(NO)₂(PPh₃)₂]⁺ and a square-pyramidal metal geometry. In solution the¹⁵N n.m.r. spectrum of a 50%¹⁵N enriched sample of [OsCl(NO)₂(PPh₃)₂]⁺ shows an equilibrium isotope effect similar to that reported for [RuCl(NO)₂(PPh₃)₂]⁺ and suggests that both complexes exist in solution as rapidly equilibrating isomeric forms.     

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Achiral P‐donor pincer‐aryl ruthenium complexes ([RuCl(PCP)(PPh₃)]) 4c , d were synthesized via transcyclometalation reactions by mixing equivalent amounts of [1,3‐phenylenebis(methylene)]bis[diisopropylphosphine] ( 2c ) or [1,3‐phenylenebis(methylene)]bis[diphenylphosphine] ( 2d ) and the N‐donor pincer‐aryl complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 2). The same synthetic procedure was successfully applied for the preparation of novel chiral P‐donor pincer‐aryl ruthenium complexes [RuCl(P*CP*)(PPh₃)] 4a , b by reacting P‐stereogenic pincer‐arenes (S,S)‐[1,3‐phenylenebis(methylene)]bis[(alkyl)(phenyl)phosphines] 2a , b (alkyl=ⁱPr or ^tBu, P*CHP*) and the complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 3). The crystal structures of achiral [RuCl(equation/tex2gif-sup-3.gifPCP)(PPh₃)] 4c and of chiral (S,S)‐[RuCl(equation/tex2gif-sup-6.gifPCP)(PPh₃)] 4a were determined by X‐ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh₃)] complexes and chiral [RuCl(P*CP*)(PPh₃)] complexes were tested as catalyst in the H‐transfer reduction of acetophenone with propan‐2‐ol. With the chiral complexes, a modest enantioselectivity was obtained.     

Impact of Group 10 Metals on the Solvent-Induced Disproportionation of o-Semiquinonato Complexes

The oxidation of [M^II(3,5-DTBCat)(DTBbpy)] (M=Ni ( [Ni] ), Pd ( [Pd] ), and Pt ( [Pt] ); 3,5-DTBCat=3,5-di-tert-butylcatecholato; DTBbpy=4,4′-di-tert-butyl-2,2′-bipyridine) afforded the dimeric {[Ni^II(3,5-DTBSQ)(DTBbpy)](PF₆)}₂ ( {[Ni](PF₆)}₂ ; 3,5-DTBSQ=3,5-di-tert-butylsemiquinonato) and monomeric semiquinonato (SQ) complexes [M^II(3,5-DTBSQ)(DTBbpy)](PF₆) (M=Pd ( [Pd](PF₆) ) and Pt ( [Pt](PF₆) )). The negative solvatochromic properties of the SQ complexes allowed us to estimate the relative order of their dipole moments: [Pd](PF₆) > [Pt](PF₆) > {[Ni](PF₆)}₂ . The complexes [Pd](PF₆) and [Pt](PF₆) adopt monomeric structures and are stable in CH₂Cl₂ and toluene, whereas they gradually disproportionate at room temperature to [M] and 3,5-di-tert-butylbenzoquinone (3,5-DTBBQ) in polar solvents such as THF, MeOH, EtOH, DMF, or DMSO. The results of spectroscopic studies suggested that the oxidized nickel complex adopts a monomeric structure ( [Ni](PF₆) ) in CH₂Cl₂, but a dimeric structure ( {[Ni](PF₆)}₂ ) in the other investigated solvents. In polar solvents, {[Ni](PF₆)}₂ may disproportionate to [Ni] and 3,5-DTBBQ at 323 K, thereby demonstrating a significant solvent- and metal-dependence in temperature. The relative activities of {[Ni](PF₆)}₂ and [M](PF₆) toward disproportionation are related to the electrochemically estimated K_dis values in CH₂Cl₂ and DMF. The present work demonstrates that solvent polarity and the dipole moments of the SQ complexes promote disproportionation, which can be controlled by a judicious choice of the metal ion, solvent, and temperature.     

Complex compounds with rhodium(III) of enantiomers of nicotine

The synthesis, characterization and comparison of the enantiomeric transition metal complexes, trans-[Rh-(S-(–)-nicH⁺)₄Cl₂](PF₆)₅ and trans-[Rh-(R-(+)-nicH⁺)₄Cl₂](PF₆)₅, and of the racemic mixture trans-[Rh-(RS-(±)-nicH⁺)₄Cl₂](PF₆)₅ are described.     

Selective Preparation of a Heteroleptic Cyclometallated Ruthenium Complex Capable of Undergoing Photosubstitution of a Bidentate Ligand

Cyclometallated ruthenium complexes typically exhibit red-shifted absorption bands and lower photolability compared to their polypyridyl analogues. They also have lower symmetry, which sometimes makes their synthesis challenging. In this work, the coordination of four N,S bidentate ligands, 3-(methylthio)propylamine (mtpa), 2-(methylthio)ethylamine (mtea), 2-(methylthio)ethyl-2-pyridine (mtep), and 2-(methylthio)methylpyridine (mtmp), to the cyclometallated precursor [Ru(bpy)(phpy)(CH₃CN)₂]⁺ (bpy=2,2′-bipyridine, Hphpy=2-phenylpyridine) has been investigated, furnishing the corresponding heteroleptic complexes [Ru(bpy)(phpy)(N,S)]PF₆ ([ 2 ]PF₆–[ 5 ]PF₆, respectively). The stereoselectivity of the synthesis strongly depended on the size of the ring formed by the Ru-coordinated N,S ligand, with [ 2 ]PF₆ and [ 4 ]PF₆ being formed stereoselectively, but [ 3 ]PF₆ and [ 5 ]PF₆ being obtained as mixtures of inseparable isomers. The exact stereochemistry of the air-stable complex [ 4 ]PF₆ was established by a combination of DFT, 2D NMR, and single-crystal X-ray crystallographic studies. Finally, [ 4 ]PF₆ was found to be photosubstitutionally active under irradiation with green light in acetonitrile, which makes it the first cyclometallated ruthenium complex capable of undergoing selective photosubstitution of a bidentate ligand.     

Study of novel η-cyclopentadienyl and η-arene platinum group metal complexes containing a N4-type ligand and their structural characterization

The mononuclear η⁵-cyclopentadienyl complexes [(η⁵-C₅H₅)Ru(PPh₃)₂Cl], [(η⁵-C₅H₅)Os(PPh₃)₂Br] and pentamethylcyclopentadienyl complex [(η⁵-C₅Me₅)Ru(PPh₃)₂Cl] react in the presence of 1 eq. of the tetradentate N,N′-chelating ligand 3,5-bis(2-pyridyl)pyrazole (bpp-H) and 1 eq. of NH₄PF₆ in methanol to afford the mononuclear complexes [(η⁵-C₅H₅)Ru(PPh₃)(bpp-H)]PF₆ ([1]PF₆), [(η⁵-C₅H₅)Os(PPh₃)(bpp-H)]PF₆ ([2]PF₆) and [(η⁵-C₅Me₅)Ru(PPh₃)(bpp-H)]PF₆ ([3]PF₆), respectively. The dinuclear η⁵-pentamethylcyclopentadienyl complexes [(η⁵-C₅Me₅)Rh(μ-Cl)Cl]₂ and [(η⁵-C₅Me₅)Ir(μ-Cl)Cl]₂ as well as the dinuclear η⁶-arene ruthenium complexes [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂ and [(η⁶-p-ⁱPrC₆H₄Me)Ru(μ-Cl)Cl]₂ react with 2 eq. of bpp-H in the presence of NH₄PF₆ or NH₄BF₄ to afford the corresponding mononuclear complexes [(η⁵-C₅Me₅)Rh(bpp-H)Cl]PF₆ ([4]PF₆), [(η⁵-C₅Me₅)Ir(bpp-H)Cl]PF₆ ([5]PF₆), [(η⁶-C₆H₆)Ru(bpp-H)Cl]BF₄ ([6]BF₄) and [(η⁶-p-ⁱPrC₆H₄Me)Ru(bpp-H)Cl]BF₄ ([7]BF₄). However, in the presence of 1 eq. of bpp-H and NH₄BF₄ the reaction with the same η⁶-arene ruthenium complexes affords the dinuclear salts [(η⁶-C₆H₆)₂Ru₂(bpp)Cl₂]BF₄ ([8]BF₄) and [(η⁶-p-ⁱPrC₆H₄Me)₂Ru₂(bpp)Cl₂]BF₄ ([9]BF₄), respectively. These compounds have been characterized by IR, NMR and mass spectrometry, as well as by elemental analysis. The molecular structures of [1]PF₆, [5]PF₆ and [8]BF₄ have been established by single crystal X-ray diffraction studies and some representative complexes have been studied by UV–vis spectroscopy.