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.     

An improved procedure for syntheses of silyl derivatives of the cubeoctameric silicate anion

The reaction of the Si₈O₂₀^8? silicate anion with X(CH₃)₂SiCl (X?H or CH₃) has been studied to develop a cost‐effective procedure for synthesizing Si₈O₂₀[Si(CH₃)₂X]₈ in high yield. Use of hexane as solvent and adjustment of the reaction temperature to ca 20 °C were found to be effective in promoting the reaction, by which Si₈O₂₀[Si(CH₃)₂X]₈ could be produced in good yield employing 24 mol of X(CH₃)₂SiCl per mole of Si₈O₂₀^8?. It was also demonstrated that the yield of Si₈O₂₀[Si(CH₃)₂X]₈ depends on the amount of solvent, suggesting that the amount is an important factor when scaling up the reaction to produce a large quantity of Si₈O₂₀[Si(CH₃)₂X]₈. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis and studies of benzoxazinesiloxanes

A synthesis of organosilicon 1,3-benzoxazines (BZ-Si) was accomplished by the reaction of organic phenols, paraformaldehyde and 3-aminopropyl(trialkoxy)silanes, as well as organosilicon phenols of the general formula R´[SiMe₂O]_n[SiMeRO]_mSiMe₂R´ (R´ is 4-hydroxy-3methoxyphenylpropyl-, R is methylor 4-hydroxy-3-methoxyphenylpropyl), paraformaldehyde, and aniline (or monoethanolamine). The structure of BZ-Si was confirmed by NMR and IR spectroscopy. The studies of BZ-Si by DSC showed that the benzoxazine ring opening takes place in the temperature range 130—265 °C. The temperature of 5% mass loss of BZ-Si in air is within 220—270 °C (TGA).     

<Emphasis Type="Italic">cis</Emphasis>-Tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes: Synthesis and mesomorphic properties

Hydrolytic condensation of organotrialkoxysilanes RSi(OR′)₃ (R = Me, Et, Pr, CH=CH₂; R′ = OMe, OEt) in the presence of sodium and/or potassium hydroxide gave new alkali organosiloxanolates {(M⁺)₄[RSi(O)O⁻]₄}·nL (R = Me, Et, Pr, CH=CH₂; M = Na, K; L = R′OH, H₂O) in which the main structural fragment is the cyclotetrasiloxanolate fragment cis-[RSi(O)O⁻]₄. Based on these organosiloxanolates, a series of cis-tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes was synthesized. For new cyclotetrasiloxanes, the thermotropic transitions and mesomorphic orderings were determined by differential scanning calorimetry, X-ray diffraction analysis, and polarization microscopy. In addition, new mesomorphic compounds were revealed. The character of thermotropic and time evolution of the phase state was found for a mixture of cis-tetra[ethyl(trimethylsiloxy)]-and cis-tetra[phenyl(trimethylsiloxy)]cyclotetrasiloxanes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 80–86, January, 2007.     

Silicon‐ and Tin‐Containing Open‐Chain and Eight‐Membered‐Ring Compounds as Bicentric Lewis Acids toward Anions

Herein, we report the syntheses of silicon‐ and tin‐containing open‐chain and eight‐membered‐ring compounds Me₂Si(CH₂SnMe₂X)₂ ( 2 , X=Me; 3 , X=Cl; 4 , X=F), CH₂(SnMe₂CH₂I)₂ ( 7 ), CH₂(SnMe₂CH₂Cl)₂ ( 8 ), cyclo‐Me₂Sn(CH₂SnMe₂CH₂)₂SiMe₂ ( 6 ), cyclo‐(Me₂SnCH₂)₄ ( 9 ), cyclo‐Me_(2?n)X_nSn(CH₂SiMe₂CH₂)₂SnX_nMe_(2?n) ( 5 , n=0; 10 , n = 1, X= Cl; 11 , n=1, X= F; 12 , n=2, X= Cl), and the chloride and fluoride complexes NEt₄[cyclo‐ Me(Cl)Sn(CH₂SiMe₂CH₂)₂Sn(Cl)Me?F] ( 13 ), PPh₄[cyclo‐Me(Cl)Sn(CH₂SiMe₂CH₂)₂Sn(Cl)Me?Cl] ( 14 ), NEt₄[cyclo‐Me(F)Sn(CH₂SiMe₂CH₂)₂Sn(F)Me?F] ( 15 ), [NEt₄]₂[cyclo‐Cl₂Sn(CH₂SiMe₂CH₂)₂SnCl₂?2 Cl] ( 16 ), M[Me₂Si(CH₂Sn(Cl)Me₂)₂?Cl] ( 17 a , M=PPh₄; 17 b , M=NEt₄), NEt₄[Me₂Si(CH₂Sn(Cl)Me₂)₂?F] ( 18 ), NEt₄[Me₂Si(CH₂Sn(F)Me₂)₂?F] ( 19 ), and PPh₄[Me₂Si(CH₂Sn(Cl)Me₂)₂?Br] ( 20 ). The compounds were characterised by electrospray mass‐spectrometric, IR and ¹H, ¹³C, ¹⁹F, ²⁹Si, and ¹¹⁹Sn NMR spectroscopic analysis, and, except for 15 and 18 , single‐crystal X‐ray diffraction studies.     

Cobalt(II) complexes of various thiosemicarbazones of 4-aminoantipyrine: syntheses,spectral, thermal and antimicrobial studies

An interesting series of cobalt(II) complexes of the new ligands: 4[N-(benzalidene)amino]antipyrinethiosemicarbazone (BAAPTS), 4[N-(2′-hydroxy-benzalidene)amino]antipyrinethiosemicarbazone (HBAAPTS) and 4[N-(2′-hydroxy-1′-naphthalidene)amino]antipyrinethiosemicarbazone (HNAAPTS) were synthesized by reaction with Co(II) salts in ethanol. The general stoichiometry of the complexes was found to be [CoX₂(H₂O)(L)] and [Co(L)₂](ClO₄)₂, where X = Cl, NO₃, NCS or CH₃COO and L = BAAPTS, HBAAPTS or HNAAPTS. The complexes were characterized by elemental analysis, molar conductivity measurement, molecular weight determination, magnetic moments at room temperature, infrared and electronic spectra. All the thiosemicarbazones behave as neutral tridentate (N, N, S) donor ligands. The conductivity measurements in PhNO₂ solution indicated that the chloro, nitrato, thiocyanato and acetate complexes are essentially non-electrolytes, while the perchlorate complexes are 1:2 electrolytes. Thermogravimetric studies were performed for some representative complexes and the decomposition mechanism proposed. Antibacterial and antifungal properties of the ligands and their cobalt(II) complexes have also been examined and it has been observed that the complexes are more potent bactericides than the ligand.     

Kinetics and Mechanism of the Reactions of Picolinic Acid with Dichloro-{1-alkyl-2-(arylazo)imidazole}palladium(II) Complexes

The reaction between Pd(N,N′)Cl₂ [N,N′ ≡ 1-alkyl-2-(arylazo)imidazole (N,N′) and picolinic acid (picH) have been studied spectrophotometrically at λ = 463 nm in MeCN at 298 K. The product is [Pd(pic)₂] which has been verified by the synthesis of the pure compound from Na₂[PdCl₄] and picH. The kinetics of the nucleophilic substitution reaction have been studied under pseudo-first-order conditions. The reaction proceeds in a two-step-consecutive manner (A → B → C); each step follows first order kinetics with respect to each complex and picH where the rate equations are: Rate 1 = {k′₀ + k′₂[picH]₀} × [Pd(N,N′)Cl₂] and Rate 2 = {k′′₀ + k′′₂[picH]₀}[Pd(N,O)(monodentate N,N′)Cl₂] such that the first step second order rate constant (k′₂) is greater than the second step second order rate constant (k′′₂). External addition of Cl⁻ (as LiCl) suppresses the rate. Increase in π-acidity of the N,N′ ligand, increases the rate. The reaction has been studied at different temperatures and the activation parameters (Δ^‡H° and Δ^‡S°) were calculated from the Eyring plot.     

Synthesis and reactivity of cyclopentadienyl ruthenium complexes containing ferrocenylselenolates

The heterotrimetallic complex 1,1′-[Fc(SeRuCp(PPh₃)₂)₂] is accessible by the reaction of 1,1′-[Fc(SeLi)₂·2THF] (Fc = Fe(η⁵-C₅H₄)₂, THF = Tetrahydrofuran) with two equivalents of CpRu(PPh₃)₂Cl in high yield. Complex 1,1′-[Fc(SeLi)₂·2THF] can be prepared by treatment of 1,1′-[Fc(SeSiMe₃)₂] with two equivalents of n-BuLi in THF solution. 1,1′-[Fc(SeRuCp(PPh₃)₂)₂] is converted to 1,1′-[Fc(SeRuCpCO(PPh₃))₂] under CO atmosphere in THF solution. The complexes 1,1′-[Fc(SeRuCp(PP))₂] [PP = Ph₂P(CH₂)PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH=CH)₂PPh₂ (dppee), Ph₂P(CH₂)₃PPh₂ (dppp)] are obtained in a one-pot reaction of CpRu(PPh₃)₂Cl and 1,1′-[Fc(SeLi)₂·2THF] with the chelating bisphosphine ligand.     

1H and13C NMR study of tin-containing sulfoxide, sulfimide, and sulfoximide

Sulfoxide RS(O)R′ (1), sulfimide RS(=NSO₂Ar)R′ (2), and sulfoximide RS(O)(=NSO₂Ar)R′ (3) (R=Me₃Sn(CH₂)₃, R′=n-C₅H₁₁, Ar=4-C₆H₄Cl) were investigated by¹H and¹³C NMR spectroscopy. Unlike 3, compounds 1 and 2 have a cyclic structure due to the intramolecular donor-acceptor S→Sn interaction. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1966–1969, November, 1997.     

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.     

A novel series of gold(III)-bis-triphenylphosphine-arylazoimidazole complexes: synthesis and spectroscopic and redox study

Reaction of [Au(PPh₃)₂(tht)₂](OSO₂CF₃)₃ with RaaiR′ in CH₂Cl₂ medium following ligand addition leads to [Au(PPh₃)₂(RaaiR′)](OTf)₃ [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), PPh₃ is triphenylphosphine, OSO₂CF₃ is the triflate anion, tht is tetrahydrothiophen]. The maximum molecular peak of the corresponding molecule is observed in the ESI mass spectrum. The ¹H-nmr spectral measurements suggest methylene, –CH₂–, in RaaiEt gives a complex AB type multiplet while in RaaiCH₂Ph it shows AB type quartets. ¹³C-nmr spectrum suggests the molecular skeleton. In the ¹H–¹H COSY spectrum as well as contour peaks in the ¹H–¹³C heteronuclear multiple-quantum coherence (HMQC) spectrum assign the solution structure. Electrochemistry assign ligand reduction part rather than metal oxidation.     

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.     

Palladium(II) complexes with R2edda-derived ligands. Part V. Reaction of O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate with K2[PdCl4]

The reaction of K₂[PdCl₄] with [(S,S)-H₂(Et)₂eddv]Cl₂ diester (O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate) (1) resulted in [PdCl₂{(S,S)-(Et)eddv-κ² N,N′,κO}] (2) complex with one hydrolyzed ester group. The compound was characterized by spectroscopic methods and it was found that the reaction is diastereoselective (¹H and ¹³C NMR; one diastereoisomer of four possible). In addition, the structure of 2 was confirmed by X-ray diffraction analysis, indicating that the product is the (R,R)–N,N′-configured isomer. DFT calculations support the formation of one diastereoisomer of 2.     

1,1-Diethynylsilacycloalkanes and Propellanes Based Thereon

Previously unknown 1,1-diethylnylsilacycloalkanes (CH₂)4nSi(C& = CH)₂ (n = 3, 4) were prepared by the reaction of HC& = CMgBr with 1,1-dichlorosilacycloalkanes (CH₂)4nSiCl₂ (n = 3, 4). The reaction of (CH₂)₄Si(C& = CMgBr)₂ with (CH2)4SiCl2 in THF under conditions of high dilution gives cyclo(tetramethylene)- silethynes [(CH2)4SiC& = C]4 with an admixture of cyclodi(tetramethylene)silethyne [(CH2)4SiC& = C]2. The re- action of Me2Si(C& = CSiMe2C& = CMgBr)2 with (CH2)4SiCl2 was used to prepare 1,1,4,4,7,7-hexamethyl-10,10- tetramethylene-1,4,4,10-tetrasilacyclododeca-2,5,8,11-tetrayne.     

Synthesis and thermal stability of silicon-containing esters of phosphorus acids

A number of trialkylsilylmethyl diphenyl phosphates MeRR′SiCH₂OP(O)(OPh)₂ (1a-e: R=Et (a), Pr (b), CF₃CH₂CH₂ (c, e), Me₃SiCH₂ (d); R′=Me (a-d), Et (e)) were synthesized and their thermal rearrangement, of the 1,2-shift type, was studied. The rearrangement consists of the migration of an alkyl group from Si atom to the methylene carbon atom and gives the corresponding silyl esters. The rate of the rearrangement was found to increase in the order1d<1b<1a<1 (R=R′=Me)<1c corresponding to the enhancement of the total inductive effect (−I) of the substituents at the Si atom. The relative migration ability of the substituents at the Si atom, determined by GC/MS analysis of the disiloxane fraction resulting from hydrolysis of pyrolyzed phosphates1a-e, increases in the order R=Pr<Et<CF₃CH₂CH₂<Me≪Me₃SiCH₂, which differs substantially from the order in which the rate of the rearrangement of phosphates1a-d changes. The electronegativity of the migrating group affects noticeably the relative ability to migrate. For Part 4, see Ref. 1. Deceased. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 1767–1772, September, 1998.     

Formation of phosphonates and pyrophosphates in the reactions of chlorophosphate esters with strong organic bases

The compounds S(6-t-Bu-4-Me-C₆H₂O)₂P(O)Cl (1), CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(O)Cl (2) and (2,2′-C₂₀H₁₂O₂)P(O)Cl (3) react with diazabicycloundecene (DBU) to give rise to, predominantly, the phosphonate compounds [S(6-t-Bu-4-Me-C₆H₆O)₂P(O)(DBU)]⁺[Cl]⁻ (4), [CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(O) (DBU)]⁺[Cl]⁻ (5) and [(2,2′-C₂₀Hi₂O₂)P(0)(DBU)]⁺[Cl]^- (6). The first two compounds could be isolated in the pure state. In analogous reactions of 1 and 2 with diazabicyclononene (DBN) or N-methyl imidazole, only the pyrophosphates [S(6-t-Bu-4-Me-C₆H₂O)₂P(O)]₂O (7) and [CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(O)]₂O (8) could be isolated, although the reaction mixture showed several other compounds in the phosphorus NMR. A possible pathway for the formation of phosphonate salts is proposed. The X-ray crystal structures of4,7 and8 are also discussed.     

Synthesis of C-functionalized acetylacetone and its europium complex. Preparation and study of luminescence of europium-containing sol-gel films

New fuctionalized ligand 3-(3′-triethoxysilylpropylaminocarbonyl)pent-2-on-3-en-4-ol (EtO)₃SiCH₂·CH₂CH₂NHC(O)-C[C(O)CH₃][=C(OH)CH₃] (I) containing ketoenol and triethoxysilyl groups is synthesized from 3-triethoxysilylpropyl isocyanate (EtO)₃SiCH₂CH₂CH₂N=C=O and acetylacetone. The reaction is accompanied by the formation of 2-(3′-triethoxysilylpropylaminocarboxy)-pent-2-en-4-one (EtO)₃SiCH₂CH₂·CH₂NHC(O)-OC(CH₃)=CH-C(O)CH₃ (II), the product of addition of acetylacetone enol form to isocyanate group. The ratio of amide I and urethane II forms is 7:3. Europium(III) tris[3-(3′-triethoxysilylpropylaminocarbonyl) pent-2-on-3-en-4-olate] is prepared from I and Eu(i-OPr)₃. An alternative pathway consists in the reaction of europium tris(acetylacetonate) with 3-triethoxysilylpropyl isocyanate. Conditions of formation of transparent europium-containing sol-gel films were developed. Thermal stability and photoluminescence of the films were investigated.     

Gold(I)-diphenylphosphinomethane–arylazoimidazole: synthesis and multinuclear NMR investigation

Reaction of [Au₂(dppm)Cl₂] with AgOTf in CH₂Cl₂ medium followed ligand addition and leads to [Au₂(dppm)(RaaiR′)](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), OSO₂CF₃ is the triflate anion, and dppm is the diphenylphosphinomethane-ring]. The ¹H-n.m.r. spectral measurements suggest methylene, –CH₂–, in RaaiEt gives a complex AB type multiplet while in RaaiCH₂Ph it shows AB type quartets with coupling constant of avg. 6 Hz. Considering all the moities there are a lot of different carbon atoms in the molecule which gives a lot of different peaks in the ¹³C-n.m.r spectrum. In the ¹H–¹H-COSY spectrum of the present complexes and contour peaks in the ¹H–¹³C-HMQC spectrum in the present complexes, assign the solution structure and stereoretentive transformation in each step.     

Synthesis of novel paracyclophanes with linear P,N-containing spacers

Condensation of bis(hydroxymethyl)mesityl-and bis(hydroxymethyl)phenylphosphines with N,N′-disubstituted bis(4-aminophenyl)methanes and bis(4-amino-3-carboxyphenyl)methane occurred as covalent self-assembly spontaneously giving a mixture of trans-and cis-diastereomers of 1,5,19,23-tetra-R′-3,21-di-R-1,5,19,23-tetraaza-3,21-diphospha[5.1.5.1]paracyclophanes as the major products. The trans-isomer (R is mesityl; R′ is methyl) was isolated in the individual state and structurally characterized by X-ray diffraction analysis. Sulfurization of macrocyclic diphosphines (R = Ph; R′ is 3-pyridylmethyl or 4-pyridylmethyl) gave the corresponding diphosphine disulfides, the trans-stereoisomer being isolated in the individual state. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1765–1774, September, 2007.     

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.