Bis-N-heterocyclic carbene ruthenium(II) carbonyl complexes: Synthesis, structural characterization and catalytic activities in transfer hydrogenation of ketones

In this contribution, the synthesis and characterization of eight ruthenium(II) carbonyl complexes supported by chelating alkane-bridged bis-N-heterocyclic carbene ligands are reported. The products obtained are analyzed using infrared and NMR spectroscopies. The molecular structures of four metal complexes were determined by X-ray crystallography, which exhibit the six-coordinate octahedral geometry with two carbene carbon atoms from the bidentate Bi-NHCs, two carbonyl groups and two chlorine atoms in the trans(Cl)-cis(CO) configuration. All these complexes show catalytic activities in transfer hydrogenation of ketones.     

Organometallic ruthenium(II)-arene complexes with triphenylphosphine amino acid bioconjugates: Synthesis,characterization and biological properties

(p-Cymene)-ruthenium bioconjugates ML (1) and ML₂ (2), bearing phosphane ligands substituted with chiral or non-chiral amino acid esters, L, were synthetized and characterized by instrumental methods (NMR, CD, MS) and DFT calculations (using the wB97xD functional). Cytotoxic activity of complexes 1 and 2 was investigated by using human cervical carcinoma cell line (HeLa) and MTT assay. Four (2_pG, 2_pA, 2_mG and 2_mA) out of ten synthesized ruthenium complexes showed significant toxicity, with IC₅₀ values of 5–30 μM. Evaluation of the potential biomolecular targets of bioconjugates 2 by UV–Vis, fluorescence and CD spectroscopy revealed no measurable interaction with DNA, but micromolar affinity for proteins. The cytotoxicity of bioconjugates 2 is in correlation with their BSA binding constants, i. e. bioconjugates with lower IC₅₀ values show higher binding affinities towards BSA. Compound 2_mG with value of IC₅₀ 16 μM was selected for further biological characterization. The higher level of toxicity towards tumor compared to normal cell lines indicates its selective activity, important characteristic for potential medical use. It was detected 2_mG caused increase of cells in the S phase of cell cycle and consequential decrease of cells in G0/G1 phase. Additionally, 2_mG caused dose- and time-dependent increase of SubG0/G1 cell population, suggesting its ability to induce programmed cell death. Further investigation determined autophagy as the mode of cell death. The role of GSH in HeLa cells response to investigated organometallic ruthenium complexes was confirmed using specific regulators of GSH synthesis, buthionine sulfoximine and N-acetyl-cysteine. Pre-treatment of cells with ethacrynic acid and probenecid emphasized the role of GSH in detoxification of 2_mG compound. The amount of total ruthenium accumulation in the cell did not correlate with toxicity of 2_pG, 2_pA, 2_mG and 2_mA, suggesting structure dependent differences in either cell uptake or kinetics of ruthenium complexes detoxification. We speculate that ruthenium complexes bind protein-based biomolecules further triggering cell death. Based on the gained knowledge, the synthesis and development of more tumor-specific ruthenium-based complexes as potential anticancer drugs can be expected.     

Structure and spectroscopic studies of cis-bis(bipyridine) ruthenium(II) complexes of phenylcyanamide ligands

New ruthenium(II) complexes with cyanamide ligands, cis-[Ru(bpy)₂(Ipcyd)₂] (1) and [Ru(bpy)₂(OHpcyd)₂] (2) (bpy = 2,2′-bipyridine, Ipcyd = 4-iodophenylcyanamide anion, OHpcyd = 4-(3-hydroxy-3-methylbut-1-ynil)phenylcyanamide), have been prepared and characterized by UV-Vis, IR and ¹H NMR spectroscopies as well as electrochemical technique (CV). The complex cis-[Ru(bpy)₂(Ipcyd)₂] (1) crystallized with empirical formula of C₃₄H₂₄I₂N₈Ru in a monoclinic crystal system and space group of P2₁/c with a = 11.769(7) Å, b = 24.188(12) Å, c = 11.623(2) Å, β = 91.63(3)°, V = 3308(3) ų and Z = 4.     

Control of the migratory aptitudes of vinyl and aryl ligands in ruthenium(II) complexes

Complexes Ru(CO)₂ (CH=CHR) (C₆H₄X-4)L₂ (R=^tBu, Ph, OEt; X=H, Cl, OMe; L=PMe₃, PMe₂Ph, P(OMe)₂Ph) in which the two phosphorus ligands are mutually cis (isomer 1) react readily with ligands ^tBuNC, CO and P(OMe)₃ to give complexes in which one of the organic ligands has migrated onto a carbonyl ligand. Vinyl migration products (5) retain the mutually cis geometry of the phosphorus ligands, and are unstable: one of the decomposition products is the ketone RCH=CHC(O)C₆H₄X-4. Phenyl migration products (4) are stable and have the phosphorus ligands in mutually trans positions; an X-ray crystal structure of Ru(CO) (CN^tBu) {C(O)Ph} (CH=CHPh) (PMe₂Ph)₂ was obtained. In both cases, the incoming ligand enters trans to the newly formed acyl ligand. Vinyl migration is favoured over aryl migration by electron-donating substituents on the vinyl ligand, electron-withdrawing substituents on the aryl ligand, good σ-donor phosphorus ligands and use of ^tBuNC as the incoming ligand. The rate of phenyl migration in Ru(CO)₂(CH=CHPh)Ph(PMe₂Ph)₂ is independent of ^tBuNC concentration: k=1.5 × 10⁻³ s⁻¹ at 20°C. Isomer 3 of complexes Ru(CO)₂(CH=CHR) (C₆H₄X-4)L₂ in which the phosphorus ligands are mutually trans is much less reactive towards migration reactions. The reactivity of isomer 1 is attributed to the steric strain of two mutually cis phosphorus ligands.     

The synthesis and characterization of mixed ligand Ru(II) complexes with dipyrido(2,3-a:3′,2′-j)phenazine (dpop′) and 2,3,5,6-tetra(2-pyridyl)-pyrazine (tppz)

The synthesis of the mixed ligand mono metallic [Ru(dpop′)(tppz)]²⁺ and bimetallic [(dpop′)Ru(tppz)Ru(dpop′)]⁴⁺ (dpop′ = dipyrido(2,3-a:3′,2′-j)phenazine; tppz = 2,3,5,6 tetra-(2-pyridyl)pyrazine) complexes is described. The [Ru(dpop′)(tppz)]²⁺ complex display an intense absorption at 518 nm which is assigned to a Ru(dπ) → dpop′ (π∗) MLCT transition, and at 447 nm which is assigned to a Ru(dπ) → tppz(π∗) MLCT transition. It undergoes emission at RT in CH₃CN with λ_em = 722 nm. The bimetallic [(dpop′)Ru(tppz)Ru(dpop′)]⁴⁺ complex shows a low energy absorption shoulder near 635 nm assigned to a Ru(dπ) → tppz(π∗) MLCT transition and an intense peak at 542 nm due to Ru(dπ) → dpop′ (π∗) MLCT transition. The bimetallic complex also emits at RT in CH₃CN with λ_em = 785 nm. Cyclic voltammetry shows reversible Ru^+2/+3 oxidations at 1.68 V for the monometallic complex and Ru^+2/+3 oxidation couples at +1.94 and +1.70 V for the bimetallic complex.     

Synthesis and characterization of ruthenium(II) complexes bearing the bis(2-pyridylmethyl)amine ligand

The reaction of [Ru(CO)₂Cl₂]_n with bis(2-pyridylmethyl)amine (bpma) in refluxing ethanol followed by anion exchange yields two products: cis,fac-[Ru(bpma)(CO)₂Cl]PF₆ (1a, 71%) and trans,fac-[Ru(bpma)(CO)₂Cl]PF₆ (1b, 29%). Reaction of 1a with AgBF₄ in acetone, followed by acetonitrile and then anion exchange gave cis,fac-[Ru(bpma)(CO)₂(CH₃CN)](PF₆)₂ (2a). In the same way, 1b afforded trans,fac-[Ru(bpma)(CO)₂(CH₃CN)](PF₆)₂ (2b). Reaction of depolymerized [Ru(CO)₂Cl₂]_n with bpma in ethanol at room temperature afforded cis,cis-[Ru(η²-bpma)(CO)₂Cl₂] (3). In refluxing ethanol, 3 was converted to cis,fac-[Ru(bpma)(CO)₂Cl]Cl (1a-Cl). Heating 3 in chlorobenzene afforded 1b-Cl, exclusively; heating 3 in ethylene glycol gave mainly 1a-Cl. Heating 1a-Cl in ethanol resulted in no isomerization, but heating in chlorobenzene gave a mixture of 3 and 1b-Cl. Anion exchange for PF₆ with 1a-Cl and 1b-Cl afforded 1a and 1b, respectively, whereas anion exchange for BPh₄ afforded 1a-BPh₄. Compounds 1a, 1b, 2a and 3 have been structurally characterized.     

Synthesis and characterization of iron and ruthenium complexes bearing P-N ligands based on 8-hydroxyquinoline

The synthesis of bidentate aminophosphine ligands (PN^quin) based on 8-hydroxyquinoline is described. These ligands react with cis-Fe(CO)₄Br₂ to give selectively octahedral complexes of the type cis,cis-Fe(PN^quin)(CO)₂Br₂. There is only one isomer formed where the two CO and the two bromide ligands adopt a cis configuration. The reaction of [RuCp(CH₃CN)₃]PF₆ with PN^quin ligands affords the halfsandwich complexes [RuCp(PN^quin)(CH₃CN)]PF₆ in high isolated yields. Likewise, treatment of [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂ with PN^quin in the presence of AgCF₃SO₃ affords halfsandwich complexes of the type [Ru(η⁶-p-cymene)(PN^quin)Cl]CF₃SO₃. All ligands and complexes are characterized by NMR and IR spectroscopy. The X-ray structure of representative compounds is reported. In addition, the relative stability of isomeric structures and conformers of Fe(PN^quin-Ph)(CO)₂Br₂ is studied by means of DFT calculations.     

Synthesis, chemical- and electrochemical properties of ruthenium(II) complexes bearing 2,6-bis(2-naphthyridyl)pyridine

Ruthenium complexes with a terpyridine-analogous ligand, 2,6-bis(2-naphthyridyl)pyridine (bnp), have been synthesized and their chemical and electrochemical properties investigated. The structures of [Ru(bnp)(tpy)](PF₆)₂ (1) and [Ru(bnp)₂](PF₆)₂ (2) were determined by the X-ray structure analysis. The bnp localized redox potentials of 1 and 2 showed significant positive shift by 260-290 mV relative to the analogous Ru-terpyridine complexes.     

Syntheses, structures and photoluminescence properties of cadmium(II) and zinc(II) complexes with pyridinylcarboxamide-containing ligand

Four new coordination complexes [Cd(DPBA-3)₂(H₂O)₂](ClO₄)₂·2H₂O (1), [Cd(DPBA-3)(DMF)(NO₃)₂]·DMF (2), [Cd₃(DPBA-3)₂(SCN)₆]·2DMF·4H₂O (3) and [Zn(DPBA-3)(SCN)₂] (4) [DPBA-3 = N,N′-di(pyridin-3-yl)pyridine-3,5-dicarboxamide] have been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction. Complexes 1, 3 and 4 exhibit three different types of one-dimensional (1D) chain structures constructed by the metal ions and DPBA-3 ligands, and the Cd(II)-DPBA-3 1D chains in 3 are further linked by bridging SCN⁻ ligands to afford a three-dimensional (3D) framework. Complex 2 possesses a (6,3) two-dimensional (2D) layer structure. In 1-4, the hydrogen bonds involving the amide groups play important role to stabilize the resultant frameworks. The photoluminescence properties of the DPBA-3 and the complexes were studied in the solid state at room temperature.     

Synthesis and characterization of ruthenium and osmium complexes of heterocyclic bidentate ligands (N, X), X = S, Se

The reaction of [RuCl₂(PPh₃)₃] and [OsBr₂(PPh₃)₃] precursors with a series of heterocyclic bidentate (N, X) ligands, X = S, Se, gave complexes [M(R-pyS)₂(PPh₃)₂], (R = H, 3-CF₃, 5-CF₃, 3-Me₃Si); [M(R-pymS)₂(PPh₃)₂], (R = 4-CF₃, 4,6-MeCF₃) and [M(R-pySe)₂(PPh₃)₂], (R = H, 3-CF₃, 5-CF₃), where M is Ru or Os, pyS and pymS the anions of pyridine-2-thione and pyrimidine-2-thione, respectively, and pySe is the anion produced by the reductive cleavage of the Se-Se bond in the dipyridyl-2,2′-diselenide. All of the compounds obtained were characterized by microanalysis, IR, FAB, NMR spectroscopy and by cyclic voltammetry. Compounds [Ru(3-CF₃-pyS)₂(PPh₃)₂] · 2(CH₂Cl₂) (2), [Ru(3-Me₃Si-pyS)₂(PPh₃)₂] (4), [Ru(4-CF₃-pymS)₂(PPh₃)₂] (5), [Ru(3-CF₃-pySe)₂(PPh₃)₂] · 2(CH₂Cl₂) (8), [Os(3-CF₃-pyS)₂(PPh₃)₂] · (CHCl₃) (11), [Os(3-Me₃Si-pyS)₂(PPh₃)₂] (13), [Os(3-CF₃-pySe)₂(PPh₃)₂] · 2(CH₂Cl₂) (17), [Os(5-CF₃-pySe)₂(PPh₃)₂] · 2(H₂O) (18) and [OsCl₂(4,6-MeCF₃-pymS)(PPh₃)₂] (19) were also characterized by X-ray diffraction. In all cases, the metal is in a distorted octahedral environment with the heterocyclic ligand acting as a bidentate (N, S) chelate system.     

The synthesis, structure, reactivity and electrochemical properties of ruthenium complexes featuring cyanoacetylide ligands

The complex [Ru(CCCN)(dppe)Cp*] (1) is readily obtained (ca. 70%) from the sequential reaction of [Ru(CCH₂)(dppe)Cp*]PF₆ with ⁿBuLi and phenyl cyanate. The complex behaves as a typical transition metal acetylide upon reaction with tetracyanoethene, affording a metallated pentacyanobutadiene. Complex 1 is a useful metalloligand, and its reactions with [W(thf)(CO)₅], [RuCl(PPh₃)₂Cp], [RuCl(dppe)Cp*] or cis-[RuCl₂(dppe)₂] all afforded products featuring the M-CCCN-M′ motif, for which ground state structures indicate a degree of polarisation. Electrochemical and spectroelectrochemical studies reveal moderate interactions between the metal centres in the 35-electron dications [{Cp*(dppe)Ru}(μ-CCCN){RuL₂Cp′}]²⁺ (RuL₂Cp′ = Ru(PPh₃)₂Cp, Ru(dppe)Cp*).     

Nickel(II) complexes bearing pyrazolylimine ligands: Synthesis, characterization, and catalytic properties for ethylene oligomerization

Four phenyl-substituted pyrazolylimine ligands 2-(C₃HN₂Me₂-3,5)(C(Ph)N(4-R₂C₆H₂(R₁)₂-2,6)) (L1: R₁ = ⁱPr, R₂ = H; L2: R₁ = H, R₂ = NO₂; L3: R₁ = R₂ = H; L4: R₁ = H, R₂ = OCH₃) were synthesized. The influences of steric bulk and electronic effect of pyrazolylimine ligands on the structures of their corresponding nickel complexes were investigated. Ligands with more bulky and electron withdrawing substituents on N-phenyl ring produced four-coordinate nickel complexes (2-(C₃HN₂Me₂-3,5))(C(Ph)(4-R₂C₆H₂(R₁)₂-2,6)NiBr₂ (1, R₁ = ⁱPr, R₂ = H; 2, R₁ = H, R₂ = NO₂)), whereas the ligands with less bulky and electron donating substituents on N-phenyl ring formed bis-pyrazolylimine dinickel tetrahalides (bis-2-(C₃HN₂Me₂-3,5))(C(Ph)N(4-R₂C₆H₂ (R₁)₂-2,6)Ni₂Br₄ (3, R₁ = R₂ = H; 4, R₁ = H, R₂ = OCH₃)) and six-coordinate nickel dihalides (bis-2-(C₃HN₂Me₂-3,5))(C(Ph)N(4-R₂C₆H₂(R₁)₂-2,6) NiBr₂ (5, R₁ = R₂ = H;6, R₁ = H, R₂ = OCH₃)). The solid-state structures of complexes 1, 4 and 5 have been confirmed by X-ray single-crystal analyses. Activated by methylaluminoxane (MAO), complexes 1, 2, 5 and 6 showed moderate to high activity for ethylene oligomerization, and complex 5 revealed the highest activity up to 8.96 × 10⁵ g oligomer/(mol Ni · h). The proportions of resultant oligomers were mainly C4-C8 and a little C10-C14 determined by gas chromatography/mass spectrometry.     

New dinuclear arene ruthenium complexes with P,S- or P,O-chelating ligands

Two equivalents of 2-diphenylphosphinobenzoic acid react with 1,2-ethanedithiol and 1,8-diaminonaphthalene under peptidic coupling conditions to give the new ligands 1,2-bis-S-[2^′-(diphenylphosphino)benzoyl]dithioethane (dppte) (1) and 1,2-bis-N-[2^′-(diphenylphosphino)benzoyl]diaminonaphthalene (dppan) (2), respectively. 1 and 2 have been characterised by mass spectrometry, elemental analysis, NMR, IR spectroscopy, and by single-crystal X-ray structure analysis. 2 is easily oxidised by air to give the monophosphine oxide derivatives (3). Single-crystal X-ray structure analysis of 3 shows an intramolecular hydrogen bond between an amido and the phosphoryl oxygen atom. Compounds 1 and 2 react with [RuCl₂(η⁶-p-cymene)]₂ to give the dinuclear complexes [RuCl(η⁶-p-cymene)(dppte)RuCl(η⁶-p-cymene)]²⁺ (4) and [RuCl(η⁶-p-cymene)(dppan)RuCl(η⁶-p-cymene)]²⁺ (5). As determined by single-crystal X-ray structure analysis, 4 and 5 adopt different coordination modes to the ruthenium atoms. In 4 the symmetric dppte ligand is P,S coordinated to the ruthenium atom, whereas in 5 the dppan ligand prefers a P,O coordination mode.     

Syntheses, crystal structures and luminescent properties of two silver complexes of N,N,N′,N′-tetra(diphenylphosphanylmethyl)ethylene diamine

Treatment of a suspension of AgNO₃ and AgCl in MeOH with a solution of N,N,N′,N′-tetra(diphenylphosphanylmethyl)ethylene diamine (dppeda) in CHCl₃ afforded a binuclear complex [Ag₂(dppeda)Cl](NO₃)·2MeOH (1). The analogous reactions using AgSCN and dppeda in EtOH/CH₂Cl₂ gave rise to a polymeric complex [Ag₂(dppeda)(SCN)₂]_n (2). Both compounds were fully characterized by elemental analyses, IR spectra, ¹H(³¹P) NMR, and single-crystal X-ray crystallography. The cation of 1 shows an interesting molecular basket framework in which dppeda adopts a side-by-side coordination mode. Compound 2 possesses an unique 2D (6,3) layer network with 34-membered metallomacrocycles in which dppeda takes a end-to-end coordination mode. The 2D topological framework of 2 is rare in the chemistry of tetraphosphines. The photoluminescent properties of 1 and 2 in solid state at ambient temperature were investigated.     

Synthesis, electrochemistry and spectroscopic properties of ruthenium phthalocyanine and naphthalocyanine complexes with triphenylarsine ligands

The synthesis, electrochemistry and spectroscopic properties of [PcRu(AsPh₃)₂] (1) and [{(tBu)₄Nc}Ru(AsPh₃)₂] (2), where Pc = phthalocyanine and Nc = naphthalocyanine are reported. These complexes are the first examples of metal phthalocyanine and naphthalocyanine complexes with axially-coordinated arsine ligands. The AsPh₃ ligands readily dissociate in non-coordinating solvents with 2 showing more rapid dissociation. In cyclic voltammetry experiments, 1 displayed three macrocycle-centred redox processes; one reduction and two oxidation processes. One reduction and three oxidation processes were observed for 2. The reduction and first oxidation are assigned to macrocycle-centred processes. The UV-Vis spectra of both complexes recorded over time showed macrocycle-centred oxidation. The oxidation was hindered by removing dioxygen from the solvent or adding excess AsPh₃.     

Spectroelectrochemical studies of some ruthenium(II) complexes with polypyridyl bridging ligands

Ruthenium(II) bis(2,2″-pyridyl) complexes with bridging ligands: 6,7-dichloro-2,3-di(2-pyridyl)quinoxaline; 2,3-di(2-pyridyl)-quinoxaline; 5-methyl-2,3-di(2-pyridyl) quinoxaline; 6,7-dibenzo-2,3-di(2-pyridyl)quinoxaline have been prepared. The electrochemical and spectroscopic properties of these complexes are reported. The resonance Raman spectroelectrochemical results indicate the presence of oxidation state sensitive marker bands in the resonance Raman spectra of the oxidized complexes. The spectroscopic data for the reduced complexes is similar for all four species. The resonance Raman data for the reduced species are dominated by 2,2″-bipyridyl vibrations.     

Synthesis,characterization and DNA binding and cleavage properties of ruthenium(II) complexes with various polypyridyls

Polypyridyl chlororuthenium(II) complexes have been synthesized and characterized. The binding mode of the complexes to DNA has been evaluated from the combined results of electronic absorption spectroscopy and viscosity measurement study. The results suggest that complexes 1, 2 and 3 bind to DNA via classical intercalation, electrostatic interaction and partial intercalation mode, respectively. Complex 2 shows less affinity for DNA. Cleavage of pUC19 DNA by complexes has been checked using gel electrophoresis. The data disclose that complex 1 has the highest cleaving ability.     

Preparation of ruthenium(II) chloride complexes of polybasic amines

The reactions of RuCl₂[P(C₆H₅)₃]₃, RuCl₂(tmeda)₂, and RuCl₂(1,5-COD)(tmeda) with polybasic amines such as pyrazole have been studied. From the phosphine complex, a binuclear complex has been isolated in which one pyrazole has been incorporated, while reactions of the latter two with excess pyrazole lead to the replacement of a tmeda ligand by two pyrazoles.     

Luminescent α-diimine complexes of ruthenium(II) containing scorpionate ligands

We describe the synthesis, characterization, and reactivity of several Ru(II) complexes of the type cis-L₂Ru(Z)ⁿ⁺, where L is an α-diimine [e.g. 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen)] ligand and Z is a bis-coordinated scorpionate ligand such as tris-(1-pyrazolyl)methane (HC(pz)₃, PZ=1-pyrazolyl; n=2) or tetrakis-(1-pyrazolyl)borate anion (B(pz)₄ ⁻; n=1). The complexes each exhibit strong visible absorption assigned as a π*(L)←dπ(Ru) metal-to-ligand charge-transfer (MLCT) transition characteristic of the cis-L₂Ru²⁺ kernel. A corresponding MLCT excited state emission is observed in room temperature CH₃CN solution, although emission energies, lifetimes, and quantum yields are reduced relative to Ru(bpy)₃ ²⁺. Electronic spectra and cyclic voltammetry measurements indicate that the relative π-acceptor abilities of the coordinated Z are: Z=(1H-pyrazolyl)₂(pz)₂B(pz)₂<(pyridine)₂<(pz)₂CH(pz). Uncoordinated pz groups of cis-(bpy)₂Ru(pz)₂B(pz)₂ ⁺ can be reacted to form a sterically hindered, localized-valence (K_com33 l mol⁻¹) cis,cis-(bpy)₂Ru^II(pz)₂B(pz)₂Ru^II(bpy)₂ ³⁺ dimer. The dimer properties are interpreted by comparison to the known cis-(bpy)₂Ru^II(pz)₂Ru^II(bpy)₂ ²⁺ analog. The dimer is photoreactive and undergoes an asymmetrical photocleavage in CH₃CN (yielding cis-(bpy)₂Ru^III(pz)₂B(pz)₂ ²⁺ and cis-(bpy)₂Ru^II(CH₃CN)₂ ²⁺), similar to the corresponding thermal reaction observed for the mixed-valence cis-(bpy)₂Ru^II(pz)₂Ru^III(bpy)₂ ³⁺ system.     

Reactivity study of arene(azido)ruthenium N∩O-base complexes with activated alkynes

Substitution reaction of chloro η⁶-arene ruthenium N∩O-base complexes [(η⁶-arene)Ru(N∩O)Cl] [N∩O = pyrazine-2-carboxylic acid (pca-H), 8-hydroxyquinoline (hq-H); arene = p-ⁱPrC₆H₄Me, N∩O = hq (1); arene = C₆Me₆, N∩O = hq (2)] with NaN₃ yield the neutral arene ruthenium azido complexes of the general formula [(η⁶-arene)Ru(N∩O)N₃] [N∩O = pca, arene = p-ⁱPrC₆H₄Me (3), arene = C₆Me₆ (4); N∩O = hq, arene = p-ⁱPrC₆H₄Me (5), arene = C₆Me₆ (6)]. These complexes undergo [3 + 2] dipolar cycloaddition reaction with activated alkynes dimethyl and diethyl acetylenedicarboxylates to yield the arene triazole complexes [(η⁶-arene)Ru(N∩O){N₃C₂(CO₂R)₂}] [N∩O = pca, R = Me, arene = p-ⁱPrC₆H₄Me (7), C₆Me₆ (8); R = Et, arene = p-ⁱPrC₆H₄Me (9), C₆Me₆ (10); N∩O = hq, R = Me, arene = p-ⁱPrC₆H₄Me (11) C₆Me₆ (12); R = Et, arene = p-ⁱPrC₆H₄Me (13), C₆Me₆ (14)]. On the bases of proton NMR study, in the above triazole complexes N(2) isomers are assigned with dimethylacetylenedicarboxylate whereas N(1) isomers with diethylacetylenedicarboxylate. All complexes have been characterized by IR and NMR spectroscopy as well as by elemental analysis. The molecular structures of the azido complexes [(η⁶-p-ⁱPrC₆H₄Me)Ru(pca)N₃] (3), [(η⁶-p-ⁱPrC₆H₄Me)Ru(hq)N₃] (5) and [(η⁶-C₆Me₆)Ru(hq)N₃] (6) have been established by single crystal X-ray diffraction studies.