1,10-(phenanthroline)-bis{1-alkyl-2-(arylazo)imidazole} ruthenium(II) perchlorate: Synthesis,spectral study,and electrochemistry

The hetero-tris-chelates of the formula [Ru(Phen)(RAaiR′)₂](ClO₄)₂ (Phen = 1,10-phenanthroline, RAaiR′ = 1-alkyl-2-(arylazo)imidazole, p-R-C₆H₄-N=N-C₃H₂-NN-1-R′, where R = H (a), Me (b), Cl (c) and R′ = Me (II), Et (III), CH₂Ph (IV)) have been isolated from the reaction of ctc-[RuCl₂(RAaiR′)₂] with AgNO₃ + Phen or [Ag(Phen)₂](ClO₄) in acetone at 40°C in dark followed by the addition of NaClO₄ (aq). The stereo-chemistry of the complexes have been supported by ¹H NMR data. Considering the arylazoimidazole and phenanthroline moietie there are twenty different carbon atoms in the molecule which gives a total of twenty different peaks in the ¹³C NMR spectrum of complex Ia. Cyclic voltammograms show Ru(III)/Ru(II) couple at 1.3–1.4 V vs SCE along with three successive ligand reductions. The article is published in the original.     

Synthesis, spectra and electrochemistry of dinitro- bis -2-(phenylazo)pyrimidine ruthenium(II). Nitro*#x2014;nitroso derivatives and reactivity of the electrophilic nitrosyl centreruthenium(II). Nitro*#x2014;nitroso derivatives and reactivity of the electrophilic nitrosyl centre

Silver-assisted aquation of bluecis-trans-cis-RuCl₂(Raapm)₂ (1a-1e) leads to the synthesis of solvento species, blue-violetcis-trans-cis-[Ru(OH₂)₂(Raapm)₂](ClO₄)₂ [Raapm =p-R-C₆H₄-N=N-C₄H₃-NN, (2a-2e), abbreviated as N,N′-chelator, where N(pyrimidine) and N(azo) represent N and N′ respectively; R = H (a),p-Me (b),p-Cl (c),m-Me (d),m-Cl (e) that react with NO₂ in warm EtOH to give violet dinitro complexes of the type, Ru(NO₂)₂(Raapm)₂ (3a-3e). The nitrite complexes are useful synthons of electrophilic nitrosyls, and on triturating the dinitro compounds with conc. HClO₄, nitro-nitrosyl derivatives are isolated. The solution structure and stereoretentive transformation in each step have been established from¹H NMR results. The compounds are redox active and display one metal-centred oxidation and successive ligand-based reductions. The v (NO) > 1900 cm^-1 strongly suggests the presence of linear Ru-N-O bonding. The electrophilic behaviour of metal-bound nitrosyl has been proved in one case by reacting with a bicyclic ketone, camphor, containing an active methylene group and an arylhydrazone with an active methine group. Diazotization of primary aromatic amines with strongly electrophilic mononitrosyl complexes in acetonotrile and dichloromethane solutions has been thoroughly studied.     

Studies on the reactivity of cis-RuCl2 fragment in Ru(PPh3)2(TaiMe)Cl2 with N,N-chelators (TaiMe = 1-methyl-2-(p-tolylazo)imidazole). Spectral and electrochemical characterisation of the products

Dechlorination of Ru(PPh₃)₂(TaiMe)Cl₂ (TaiMe = p-Me-C₆H₄-N=N-C₃H₂NN(1)-Me (1), 1-methyl-2-(p-tolylazo)imidazole) has been carried out in acetone solution by Ag⁺ and reacted with N,N’-chelators to synthesise [Ru(PPh₃)₂ (TaiMe)(N,N’)]²⁺. The complexes have been isolated as their perchlorate salts. The N,N’ chelators are 1-alkyl-2-(phenylazo)imidazoles (PaiX, X = Me, Et, CH₂Ph); 2-(arylazo)pyridines, (Raap,p-R-C₆H₄-N=N-C₅H₄N; R = H, Me, Cl); 2-(arylazo)pyrimidines (Raapm,p-R-C₆H₄-N=N-C₃N₂H₂; R = H, Me, Cl); 2,2’-bipyridine (bpy) and 1,10-phenanthroline (o-phen). Unsymmetrical N,N’ chelators may give two isomers and this is indeed observed. The¹H NMR spectral data refer to the presence of two isomers in the mixture in different proportions. With consideration of coordination pairs in the order of PPh₃, PPh₃; N,N (N refers to N(immidazole)) and N’,N (N’ refers to N(azo)), the complexes have been characterised astrans-cis-cis andtrans-trans-trans configuration; the former predominates in the mixture. Electrochemical studies exhibit high potential Ru(III)/Ru(II) couple and quasireversible N=N reduction. Electronic spectra show high intensity (ε ∼ 10⁴) MLCT transition in the visible region (520 ±10) nm along with a shoulder (ε ∼ 10³) in the longer wavelength region.     

Ruthenium(II) phenylazopyridinearylazoimidazoles: Synthesis, spectral studies and redox properties

Tris-chelate complex [Ru(Pap)(RAaiR′)₂](ClO₄)₂ (I, II, III/a, b, c) (where RAaiR′ = 1-alkyl-(2-arylazo)imidazole, R = H, Me, Cl (a, b, c); R′ = Me, Et, CH₂Ph (I, II, III), and Pap = phenylazopyridine) was prepared by silver assisted synthetic route. IR spectra of the complexes support Ru-azo nitrogen π-bonding interaction. ¹H NMR spectra suggest that there are two types of streochemical orientation of RAaiR′ around ruthenium(II). Cyclic voltammetry of the complexes shows one metal oxidation Ru(II)/Ru(III) at 1.4–1.5 V and three successive ligand reduction couples at the negative side of the reference potential in the range from −0.5 to −0.56, −0.7 to −0.8, and from −1.25 to −1.40 V, respectively. The text was submitted by the author in English.     

Gold(I)-triphenylphosphine-arylazoimidazole: Synthesis and spectral (H,C, COSY,HMQC NMR) characterization

The reaction of [Au(OSO₂CF₃)(PPh₃)] with arylazoimidazole in dichloromethane followed by NH₄PF₆ leads to [Au(RAaiR′)(PPh₃)]PF₆ (RAaiR′ = p-R-N=N-C₃H₂-NN-1-R′), abbreviated as N,N′/-chelator, where N (imidazole) and N (azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c), and R′ = Me (I), CH₂CH₃ (II), CH₂Ph (III)]. IR spectra of the complexes show -C=H- and -N=N-stretchings at 1590 and 1370 and at 1100, 755, 695, 545, and 505 cm⁻¹ due to the presence of the triphenylphosphine ring. The ¹H NMR spectral measurements suggest that methylene (-CH₂-) in (RAai)Et gives a complex of the AB type multiplet with a coupling constant of ∼7.6 Hz while in RAaiCH₂Ph it shows AB type quartets with coupling constant of av. 7.2 Hz. Considering the arylazoimidazole moity, there are different carbon atoms in the molecule giving different peaks in the ¹³C NMR spectrum of the complexes. In the ¹H-¹H COSY spectrum of the present complexes, the absence of any off-diagonal peaks extending from δ = 14.12 and 9.55 ppm confirms their assignment of no proton on N(1) and N(3), respectively. Contour peaks in the ¹H-¹³C HMQC spectrum in the present complexes, the absence of any contours at δ = 157.12, 160.76, 155.67, and 157.68–160.2 ppm assign them to the C(2), C(6), C(12), and C(PPh₃) carbon atoms, respectively. The solution structure and stereoretentive transformation in each step have been established from the ¹H NMR results. The article was submitted by the authors in English.     

Ruthenium-azoimine-chloranilates Synthesis,Spectra and Electrochemistry of Ruthenium(II)-1-alkyl-2-(arylazo)imidazole-chloranilate Complexes

Ag⁺-assisted dechlorination of blue cis-trans-cis Ru(R-aai-R′)₂Cl₂ followed by the reaction with chloranilic acid (H₂CA) in the presence of Et₃N, gives a neutral mononuclear violet complex [Ru(R-aai-R′)₂(CA)]. [R-aai-R′=p-R-C₆H₄—N=N—C₃H₂—NN, abbreviated as an N,N′ chelator where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), OMe (b), NO₂ (c) and R′= Me (4), Et(5), Bz(6)]. All the complexes exhibit strong intense MLCT transitions in the visible region and weak broad bands at higher wavelength (>700 nm). Visible transitions (580–595 nm) show a negative solvatochromic effect. The cyclic voltammograms show two quasireversible to irreversible couples positive to SCE and are due to CA⁻/CA²⁻ (1.2–1.35 V) and Ru(III)/Ru(II) (1.6–1.8 V) redox processes. Three couples, negative to SCE, are assigned to CA²⁻/CA³⁻ (−0.2 to −0.3 V), and azo reductions (−0.5 to −0.7, −0.8 to −0.9 V) of the chelated R-aai-R′.     

Synthesis,Spectra and Electrochemistry of Dinitro-bis-{1-alkyl-2-(arylazo) imidazole} Ruthenium(II). Nitro-nitroso Derivatives and Reactivity of the Electrophilic {Ru-NO}<Superscript>6</Superscript>System

Ag⁺ assisted aquation of blue cis-trans-cis-RuCl₂(RaaiR′)₂ (4–6) leads to the synthesis of solvento species, blue-violet cis-trans-cis-[Ru(OH₂)₂(RaaiR′)₂](ClO₄)₂ [Raai R′=p-R-C₆H₄ N=N–C₃H₂–NN–1–R′, (1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), OMe (b), NO₂ (c) and R′ = Me (1/4/7/10), CH₂CH₃ (2/5/8/11), CH₂Ph (3/6/9/12)] that have been reacted with NO₂⁻in warm EtOH resulting in violet dinitro complexes of the type, Ru(NO₂)₂(RaaiR′)₂ (7–9). The nitrite complexes are useful synthons of electrophilic nitrosyls, and on triturating the compounds, (7b–9b) with conc. HClO₄ nitro-nitrosyl derivatives, [Ru(NO₂)(NO)(OMeaaiR′)₂](ClO₄)₂ (10b–12b) are isolated. The solution structure and stereoretentive transformation in each step have been established from ¹H n.m.r. results. All the complexes exhibit strong MLCT transitions in the visible region. They are redox active and display one metal-centred oxidation and successive ligand-based reductions. The redox potentials of Ru(III)/Ru(II) (E_1/2^M) of (10b–12b) are anodically shifted by ∼ ∼0.2 V as compared to those of dinitro precursors, (7b–9b). The ν(NO) >1900 cm⁻¹ strongly suggests the presence of linear Ru–NO bonding. The electrophilic behaviour of metal bound nitrosyl has been proved in one case (12b) by reacting with a bicyclic ketone, camphor, containing an active methylene group and an arylhydrazone with an active methine group, and the heteroleptic tris chelates thus formed have been characterised.     

Ruthenium-mediated Selective Aromatic Thiolation in the Complex [RuII{o-S—C6H4-(p-R-)—N=N—C3H2NN(1)—R′}2]. Synthesis, Spectroscopic, e.p.r., Electro-chemical Characterization and Spectro-electrochemical Correlation

The reaction of ctc-[Ru(RaaiR′)₂Cl₂] (3a–3i) [RaaiR′=1-alkyl-2-(arylazo)imidazole, p-R—C₆H₄—N=N— C₃H₂NN(1)—R′, R=H, OMe, NO₂, R′=Me, Et, Bz] with KS₂COR′′ (R′′=Me, Et, Pr, Bu or CH₂Ph) in boiling dimethylformamide afforded [Ru^II{o-S—C₆H₄(p-R-)—N=N—C₃H₂NN(1)—R′}₂] (4a–4i), where the ortho-carbon atom of the pendant phenyl ring of both ligands has been selectively and directedly thiolated. The newly formed tridentate thiolate ligands are bound in a meridional fashion. The solution electronic spectra exhibit a strong MLCT band near 700 nm and near 550 nm, respectively in DCM. The molecular geometry of the complexes in solution has been determined by H n.m.r. spectroscopy. Cyclic voltammograms show a Ru(II)/Ru(III) couple near 0.4 V and an irreversible oxidation response near 1.0 V due to oxidation of the coordinated thiol group, along with two successive reversible ligand reductions in the range −0.80–0.87 V (one electron), −1.38–1.42 V (one electron). Coulometric oxidation of the complexes at 0.6 V versus SCE in CH₂Cl₂ produced an unstable Ru(III) congener. When R=Me the presence of trivalent ruthenium was proved by a rhombic e.p.r. spectrum having g₁=2.349, g₂=2.310.     

Ruthenium(II)-arylazoimidazole-8-hydroxyquinolinate complexes: Synthesis,spectral study (H,C, COSY,HMQC-NMR) and redox properties

The reaction of [Ru(OH₂)₂(RaaiR′)₂]²⁺ (RaaiR′ = 1-alkyl-2-(arylazo)imidazole, p-R-C₆H₄-N=N-C₃H₂NN(1)-R′, R = H (1), Me (2), Cl (3); R′ = Me (a), Et (b), CH₂Ph (c)) with 8-quinolinol (HQ) in acetone solution followed by the addition of NH₄PF₆ has afforded violet coloured mixed ligand complexes of the composition [Ru(Q)(RaaiR′)₂](PF₆). The maximum molecular peak of 1b is observed at m’z 790 (50%) in the ESI mass spectrum. Ir spectra of the complexes show -C=N- and -N=N- stretching near at 1590 and 1370 cm⁻¹. The ¹H NMR spectral measurements suggest methylene, -CH₂−, in RaaiEt gives a complex AB type while in RaaiCH₂Ph it shows AB type quartets. Considering the arylazoimidazole and oxine moitie there are twenty different carbon atoms in the molecule which gives a total of twenty different peaks in the C¹³ NMR spectrum of complex 1a. In the ¹H-¹H COSY spectrum of the present complexes, absence of any off-diagonal peaks extending from δ = 14.12 and 9.55 ppm confirm their assignment of no proton on N(1) and N(3) respectively. Contour peaks in the ¹H-¹³C HMQC spectrum in the present complexes, the absence of any contours at δ = 157.12, 160.76, 155.67 ppm and 157.68–160.2 ppm assign them to the C(2), C(6), C(g) and C(h), C(i) carbon atoms respectively. The solution structure and stereoretentive transformation in each step have been established from n.m.r. results. Cyclic voltammograme show a Ru(III)/Ru(II) couple at 1.0–1.1 V versus SCE along with three successive ligand reductions.     

A novel series of nickel(II)-dppe-arylazoimidazole complexes. Synthesis and spectroscopic characterization

Reaction of [Ni(dppe)Cl₂/Br₂] with AgOTf in CH₂Cl₂ medium following ligand addition leads to [Ni(dppe)(OSO₂CF₃)₂] and then [Ni(dppe)(RaaiR)](OSO₂CF₃)₂ [RaaiR′ = p–R–C₆H₄–N=N–C₃H₂–NN-1–R′,(1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), OSO₂CF₃ is the triflate anion]. ³¹P{¹H}-NMR confirm that stable bis-chelated square planar Ni(II) azoimine–dppe complex formation with one sharp peaks. The ¹H NMR spectral measurements suggest azoimine link is present with lot of phenyl protons in the aromatic region. Considering all the moities there are a lot of different carbon atoms in the molecule which gives many different peaks in the ¹³C(¹H)-NMR spectrum. In the ¹H-¹H COSY spectrum in the present complexes and contour peaks in the ¹H-¹³C-HMQC spectrum in the present complexes, assign the solution structure and stereoretentive conformation in each complexes.     

Chemistry of ruthenium in N2P2X2 (X = Cl, Br) coordination sphere: Synthesis, characterization and reactivities

Reaction of 2-(phenylazo)pyridine (pap) with [Ru(PPh₃)₃X₂] (X = Cl, Br) in dichloromethane solution affords [Ru(PPh₃)₂(pap)X₂]. These diamagnetic complexes exhibit a weakdd transition and two intense MLCT transitions in the visible region. In dichloromethane solution they display a one-electron reduction of pap near − 0.90 V vs SCE and a reversible ruthenium(II)-ruthenium(III) oxidation near 0.70 V vs SCE. The [Ru^III(PPh₃)₂(pap)Cl₂]⁺ complex cation, generated by coulometric oxidation of [Ru(PPh₃)₂(pap)Cl₂], shows two intense LMCT transitions in the visible region. It oxidizes N,N-dimethylaniline and [Ru^II(bpy)₂Cl₂] (bpy = 2,2′-bipyridine) to produce N,N,N′,N′-tetramethylbenzidine and [Ru^III(bpy)₂Cl₂]⁺ respectively. Reaction of [Ru(PPh₃)₂(pap)X₂] with Ag⁺ in ethanol produces [Ru(PPh₃)₂(pap)(EtOH)₂]²⁺ which upon further reaction with L (L = pap, bpy, acetylacetonate ion(acac⁻) and oxalate ion (ox²⁻)) gives complexes of type [Ru(PPh₃)₂(pap)(L)]ⁿ⁺ (n = 0, 1, 2). All these diamagnetic complexes show a weakdd transition and several intense MLCT transitions in the visible region. The ruthenium(II)-ruthenium(III) oxidation potential decreases in the order (of L): pap > bpy > acac⁻ > ox²⁻. Reductions of the coordinated pap and bpy are also observed.     

Multinuclear NMR investigation on organometallic gold(III) pentafluorophenylarylazoimidazole complexes

Reaction of [Au(C₆F₅)(tht)₂Cl](OTf) with RaaiR′ in CH₂Cl₂ medium leads to [Au(C₆F₅)(RaaiR′)Cl](OTf) [RaaiR′ = p-R–C₆H₄–N=N–C₃H₂–NN-1-R′, (1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), tht is tetrahydrothiophen]. The maximum molecular peak of [Au(C₆F₅)(MeaaiMe)Cl] is observed at m/z 599.51 (100 %) in the FAB mass spectrum. Ir spectra of the complexes show –C=N– and –N=N– stretching near at 1590 and 1370 cm⁻¹ and near at 1510, 955, 800 cm⁻¹ due to the presence of pentafluorophenyl ring. The ¹H-NMR spectral measurements suggest methylene, –CH₂–, in RaaiEt gives a complex AB type multiplet while in RaaiCH₂Ph shows AB type quartets. ¹³C-NMR spectrum of complexes confirm the molecular skeleton. In the ¹H-¹H-COSY spectrum as well as contour peaks in the ¹H-¹³C HMQC spectrum for the present complexes, assign the solution structure and stereoretentive conformation. The electrochemistry gives the ligand reduction peaks.     

Ruthenium(II) nitro-nitroso-bis-{1-(alkyl)-2-(β-napthylazo)imidazole}: Synthesis,spectroscopy, electrochemistry and reactivity

Aquation of blue cis-trans-cis-[RuCl₂(β-NaiR)₂] (1) leads to the synthesis of solvento species, blue-violet cis-trans-cis-[Ru(OH₂)₂(β-NaiR)₂](ClO₄)₂ (2), [β-NaiR = C₁₀H₇-N=N-C₃H₂-NN, abbreviated as N,N′-chelator, R = Me] that have been reacted with NaNO₂ in warm EtOH resulting in violet dinitro complexes of the type, [Ru(NO₂)₂(β-NaiR)₂] (3). The nitrite complexes are useful synthons of electrophilic nitrosyls, and on triturating the dinitro compounds with cone. HClO₄ nitro-nitrosyl derivatives, [Ru(NO₂)(NO)(β-NaiR)₂]²⁺ (4) are isolated. The chemical oxidation of aqua complex (2) by excess aqueous eerie solution in 1 (N) H₂SO₄ leads to the spontaneous formation of a yellow colored species. The electrophilic behaviour of metal bound nitrosyl has been proved by reacting with a bicyclic ketone, camphor, containing an active methylene group and an arylhydrazone with an active methine group. The diazotization of the primary aromatic amines with a strongly electrophilic mononitrosyl complex in acetonotrile and dichloromethane solution was thoroughly studied. Electrocatalytic oxidation of benzyl alcohol was examined.     

Palladium(II)-dppe-arylazoimidazole complexes: Synthesis,and spectroscopic characterization

Reaction of [Pd(dppe)Cl₂/Br₂] with AgOTf in a dichloromethane medium followed by ligand addition led to [Pd(dppe)(OSO₂CF₃)₂] and then [Pd(dppe)(RaaiR)](OSO₂CF₃)₂ [RaaiR′ = p-R-C₆H₄-N=N-C₃H₂-NN-1-R′, (1–3), abbreviated as a N,N′-chelator, where N(imidazole) and N(azo) are represented by N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), OSO₂CF₃ is the triflate anion, dppe = 1,2-bis-(diphenylphosphinoethane)]. ³¹P “¹H” NMR confirmed that due to the two phosphorus atom interaction in the azoimine symmetrical environment one sharp peak was formed. The ¹H NMR spectral measurements suggest that azo-imine link with lot of phenyl protons in the aromatic region. ¹³C (¹H) NMR spectrum, ¹H, ¹H COSY and ¹H, ¹³C HMQC spectrum assign the solution structure and stereo-retentive conformation in each complex.     

Studies on solid state synthesis and the oxygenation property of cobalt (II) Schiff base (vanilline polyamine) complexes

Three new cobalt complexes were synthesized by solid-state reaction at room temperature and the resultant Co complexes reacted with two equivalent oxygen molecules at room temperature to produce the oxygenated complexes [Co·(L₁)₂·(O₂)₂](NO₃)₂·2H₂O (L₁ = N, N’-bis(4-hydroxyl-3-methoxy-benzyl)-diethylenetriamine), [Co·(L₂)₂·(O₂)₂](NO₃)₂·2H₂O (L₂ = N, N’-bis(4-hydroxyl-3-methoxy-benzyl)-triethylenetetramine), and [Co·(L₃)₂·(O₂)₂](NO₃)₂·2H₂O (L₃ = N, N’-bis(4-hydroxyl-3-methoxy-benzyl-tetraethylenepentamine). The oxygenated complexes were characterized by elemental analysis, IR (Infrared), ¹H-NMR (Nuclear Magnetic Resonance), and UV-Vis (Ultraviolet Visual) spectrometry, and TG/DTA (Thermogravimetry/Differential Thermal Analysis) analysis, and molar conductance. The coordinated oxygen contents in the oxygenated complexes were also determined by weight method. It was supposed that only one O₂ molecule coordinated to the Co ion forming a superoxo type oxygenated complex. Translated from Acta Chimica Sinica, 2006, 64(15): 1517–1522 (in Chinese)     

Synthesis and multinuclear NMR investigation on gold(III)-triphenylphosphine-pentafluorophenyl-arylazoimidazole

Reaction of [Au(C₆F₅)(PPh₃)(OSO₂CF₃)₂] with RaaiR′ in dichloromethane medium followed ligand addition leads to [Au(PPh₃)(C₆F₅)(RaaiR′)](OSO₂CF₃)₂ where RaaiR′ = p-R-C₆H₄-N=N-C₃H₂-NN-1-R′ (I–III), abbreviated as N, N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (I), CH₂CH₃ (II), CH₂Ph (III), PPh₃ is triphenylphosphine, OSO₂CF₃ is the triflate anion. The maximum molecular peak of the corresponding molecule is observed in the ESI mass spectrum. IR spectra of the complexes show -C=N- and -N=N- stretching near at ∼1590 and 1370 cm⁻¹ and at ∼1100, 755, 695, 545, and 505 cm⁻¹ due to the presence of triphenylphosphine and pentafluoropheny ring. The ¹H NMR spectral measurements suggest methylene (-CH₂-) in RaaiEt that gives a complex AB type multiplet with coupling constant of av. 6.6 Hz while in RaaiCH₂Ph it shows AB type quartets with coupling constant of av. 6.2 Hz. Considering all the moitie there are a lot of different carbon atoms in the molecule which gives a lot of eleven different peaks in the ¹³C {¹H}NMR spectrum. In the ¹H-¹H COSY NMR spectrum of the present complexes and contour peaks in the ¹H-¹³C HMQC NMR spectrum in the present complexes, assign the solution structure and stereo-retentive transformation in each step. The article is published in the original.     

Synthesis, spectral characterization and redox properties of iron (II) complexes of 1-alkyl-2-(arylazo)imidazole

Iron (II) complexes of 1-alkyl-2-(arylazo)imidazoles (p-R-C₆H₄-N=N-C₃H₂NN-1-R′, R = H (a), Me (b), Cl (c) and R′ = Me (1/3), Et (2/4) have been synthesized and formulated astris-chelates Fe(RaaiR′) ₃ ²⁺ . They are characterized by microanalytical, conductance, UV-Vis, IR, magnetic (polycrystalline state) data. The complexes are low spin in character,t _2g ⁶ (Fe(II)) configurations.     

Synthesis, spectral and electrochemical behaviour of cytosinato bridged complexes of ruthenium(II) and platinum(II) with 1-alkyl-2-(arylazo)imidazoles

Dechlorination of M(RaaiR′) _n Cl₂ by AgNO₃ produced [M(RaaiR′) _n (MeCN)₂]⁺² [M = Ru(II), n = 2; Pt(II), n = 1; RaaiR′ = 1-alkyl-2-(arylazo)imidazole)] which upon reaction with the nucleobase cytosine (C) in MeCN solution gave cytosinato bridged dimeric compounds which were isolated as perchlorate salts [M₂(RaaiR′) _n (C)₂](ClO₄)₂ · H₂O. The products were characterized by IR, u.v.–vis., ¹H-n.m.r. spectroscopy and cyclic voltammetry. In MeCN solution the ruthenium complexes exhibit a strong MLCT band at 550–555 nm and two redox couples positive to SCE due to two metal-center oxidation along with ligand reduction, negative to SCE. The platinum complexes show a weak transition at 500–520 nm in MeCN and exhibit only ligand reduction in cyclic voltammetry. The coordination of the ligand was supported by ¹H-n.m.r. spectral data.     

Thiosemicarbazonates of Ruthenium(II): Crystal Structures of [Bis(triphenylphosphine)][bis(N‐phenyl‐pyridine‐2‐carbaldehyde Thiosemicarbazonato)]ruthenium(II) and [Bis(diphenylphosphino)butane][bis(salicylaldehyde Thiosemicarbazonato)]ruthenium(II)

Reaction of RuCl₂(PPh₃)₃ with N‐Phenyl‐pyridine‐2‐carbaldehyde thiosemicarbazone (C₅H₄N–C²(H)=N³‐N²H–C¹(=S)N¹HC₆H₅, Hpytsc‐NPh) in presence of Et₃N base led to loss of ‐N²H‐proton and yielded the complex [Ru(pytsc‐NPh)₂(Ph₃P)₂] ( 1 ). Similar reactions of precursor RuCl₂[(p‐tolyl)₃P]₃ with a series of thiosemicarbazone ligands, viz. pyridine‐2‐carbaldehyde thiosemicarbazone (Hpytsc), salicylaldehyde thiosemicarbazone (H₂stsc), and benzaldehyde thiosemicarbazone (Hbtsc), have yielded the complexes, [Ru(pytsc)₂{(p‐tolyl)₃P}₂] ( 2 ), [Ru(Hstsc)₂{(p‐tolyl)₃P}]₂ ( 3 ), and [Ru(btsc)₂{(p‐tolyl)₃P}₂] ( 4 ), respectively. The reactions of precursor Ru₂Cl₄(dppb)₃ {dppb = Ph₂P–(CH₂)₄–PPh₂} with H₂stsc, Hbtsc, furan‐2‐carbaldehyde thiosemicarbazone (Hftsc) and thiophene‐2‐carbaldehyde thiosemicarbazone (Httsc) have formed complexes of the composition, [Ru(Hstsc)₂(dppb)] ( 5 ), [Ru(btsc)₂(dppb)] ( 6 ), [Ru(ftsc)₂(dppb)] ( 7 ), and [Ru(ttsc)₂(dppb)] ( 8 ). The complexes have been characterized by analytical data, IR, NMR (¹H, ³¹P) spectroscopy and X‐ray crystallography ( 1 and 5 ). The proton NMR confirmed loss of –N²H– proton in all the compounds, and ³¹P NMR spectra reveal the presence of equivalent phosphorus atoms in the complexes. In all the compounds, thiosemicarbazone ligands coordinate to the Ru^II atom via hydrazinic nitrogen (N²) and sulfur atoms. The arrangement around each metal atom is distorted octahedral with cis:cis:trans P, P:N, N:S, S dispositions of donor atoms.     

Synthesis and Characterization of Some Ru( tmeda ) Complexes Containing Chloride, Hydride, and Vinylidene Ligands

 The polymeric compound [Ru(cod)Cl₂] _x (cod = cyclooctadiene) reacts with 2 equivalents of tmeda (N,N,N′,N′-tetramethylethylenediamine) in refluxing MeOH to afford trans-[Ru(cod)(tmeda)(Cl)(H)] (1), which upon treatment with CHCl₃ is readily converted to the dichloro complex trans-[Ru(cod)(tmeda)Cl₂] (2). When [Ru(cod)Cl₂] _x is reacted with tmeda under an atmosphere of H₂ (3 bar), the bis-tmeda complex trans-[Ru(tmeda)₂Cl₂] (3) is obtained in 80% yield. DFT calculations revealed that 3 is by 52 kJ/mol more stable than the corresponding cis isomer. Attempts to prepare the coordinatively unsaturated complex [Ru(tmeda)₂Cl]⁺ by reacting 1 with TICF₃SO₃ were unsuccessful. According to DFT calculations, however, such a complex should be stable and, interestingly, should adopt a square pyramidal rather than a trigonal bipyramidal structure. If halide abstraction of 3 is performed in the presence of terminal alkynes HC*CR (R*t-Bu, n-Bu), the cationic vinylidene complexes [Ru(tmeda)₂(Cl)(*C*CHR)]⁺ (4a,b) are obtained.