共查询到20条相似文献,搜索用时 15 毫秒
1.
P. Byabartta 《Russian Journal of Coordination Chemistry》2009,35(9):687-691
Silver-assisted aquation of blue cis-trans-cis-RuCl2(RAaiR’)2 (I) leads to the synthesis of solvento species, blue-violet cis-trans-cis-[Ru(OH2)2(RAaiR’)2](ClO4)2 (II), where RAaiR’ = p-R-C6H4-N=N-C3H2-NN, abbreviated as N,N′ chelator (N(imidazole) and N(azo) represent N and N′, respectively); R = H (a), p-Me (b), p-Cl(c); R′ = Me (III), Et (IV), Bz (V), that reacted with NCS− in warm EtOH resulting in red-violet dithiocyanato complexes of the type [Ru(NCS)2(RAaiR)2] (IIIa–Vn). These complexes were studied by elemental analysis, UV-Vis, IR, and 1H NMR spectroscopy and cyclic voltammetry. The solution structure and stereoretentive transformation in each step have been
established from 1H NMR results. All the complexes exhibit strong MLCT transitions in the visible region. They are redox active and display
one metal-centered oxidation and successive ligand-based reductions. Linkage isomerisation was studied by changing the solvent
and then by UV-Vis spectral analysis. 相似文献
2.
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. 相似文献
3.
Rauth Goutam Kumar Pal Sanjib Das Debasis Sinha Chittaranjan 《Transition Metal Chemistry》2001,26(6):679-684
1-Benzyl-2-(arylazo)imidazoles, p-RC6H4N=NC3H2-N21-CH2Ph [RaaiBz (2); R=H(a), Me(b), Cl(c)], react with K2PtCl4 in boiling MeCN–H2O (1:1 v/v) to give brownish-red Pt(RaaiBz)Cl2
(3) complexes. Addition of dioxolene in the presence of Et3N to a CHCl3–MeOH solution of Pt(RaaiBz)Cl2 yields green mixed complexes of composition [Pt(RaaiBz)(O,O)] [O,O = catecholate (cat) (4); 4-tert-butylcatecholate (tbcat), (5); 3,5-di-tert-butylcatecholate (dtbcat), (6); tetracholorocatecholate (tccat), (7)] which were characterised by elemental analyses, i.r., u.v.–vis.–near i.r. and 1H-n.m.r. spectral data. The solution electronic spectra exhibit ligand-to-ligand charge-transfer (l.l.c.t) transitions in the red to near i.r. region; the position and symmetry of the band depend upon the substituent on the dioxolene and arylazoimidazole. This effect is qualitatively assigned as HOMO(dioxolene) LUMO(RaaiBz). A cyclic voltammogram of the dioxolene complex reveals two consecutive oxidative couples corresponding to catechols to semiquinones and semiquinone to quinone, respectively and the reductive couples represent azo reductions. 相似文献
4.
Sushanta Saha Prodyut Kumar Sarkar Ambikesh Mahapatra 《Transition Metal Chemistry》2006,31(3):389-395
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. 相似文献
5.
Ru(PPh3)3Cl2 reacts with N(1)-alkyl-2-(arylazo)imidazoles, p-RC6H4N=NC3H2N2X, [RaaiX, R = H(a), Me(b), Cl(c); X = Me(1), Et(2), Bz(3)] under refluxing conditions in EtOH to give [Ru(RaaiX)2(PPh3)2](ClO4)2 · H2O complexes (4–6). RaaiX is a bidentate chelator (N, N) with N(imidazole), N and N(azo), N donor centres. Three isomers are present in the mixture in which the pairs of PPh3, N and N occupy cis–cis–trans, cis–trans–cis and cis–cis–cis, positions respectively. The isomers were identified by 1H-n.m.r. spectra. Four signals are observed in the aliphatic zone for N(1)-X; two are of equal intensity at higher and the other two signals at lower in the ratio 1:0.3:0.2 suggesting the presence of cis–cis–cis, cis–trans–cis and cis–cis–trans-geometry. The complexes display the allowed t
2(Ru)
*(RaaiX) transition. Cyclic voltammetry indicates two consecutive RuIII/II couples along with azo reductions. 相似文献
6.
Seikh Jasimuddin 《Transition Metal Chemistry》2006,31(6):724-729
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. 相似文献
7.
Prithwiraj Byabartta 《Transition Metal Chemistry》2005,30(7):804-813
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) (E1/2M) 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. 相似文献
8.
Misra Tarun Kumar Santra Prasanta Kumar Sinha Chittaranjan 《Transition Metal Chemistry》1999,24(6):672-677
Complexes of N(1)-methyl- and N(1)-benzyl-2-(dimethylphenylazo)imidazoles with ruthenium(II) have been prepared and characterised by physico-chemical and spectroscopic means. The 7,8-dimethylphenylazo ligands gave four stereoisomers, whereas the 8,9-dimethylphenylazo ligands gave only two. Isomer assignments are made on the basis of i.r. and 1H-n.m.r. data. Redox studies show the RuIII/II couple at 0.4–0.5 V (versus s.c.e) for the trans,cis,cis-isomers, whereas the other isomers exhibit higher (0.6–0.7 V) potentials. Two successive azo reductions are observed at negative potentials. The difference between the first metal and ligand redox potentials is linearly correlated with CT [t2(Ru) *(RL)]. 相似文献
9.
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′. 相似文献
10.
Rauth Goutam Kumar Das Debasis Sinha Chittaranjan Bag Kanchan Mahapatra Ambikesh 《Transition Metal Chemistry》2002,27(6):639-645
The reaction of dichloro{1-methyl-2-(arylazo)imidazole}palladium(II), Pd(RaaiMe)Cl2 where RaaiMe = p-R–C6H4N=N–C3H2N2-1-Me; R = H(1), Me(2), Cl(3), with pyridine bases [RPY: R = H (a), 4-Me (b), 4-Cl (c), 2-Me (d), 2,6-Me2
(e), 2,4,6-Me3
(f)] has been studied spectrophotometrically in MeCN at 451 nm. The products (4) have been isolated and characterised as trans-Pd(RPy)2Cl2. The kinetics of the nucleophilic substitution has been examined under pseudo-first-order conditions at 298 K. A single phase reaction step has been observed for bases such as Hpy (a), 4-MePy (b) and 4-ClPy (c) and follows the rate law: rate = (a + k[RPy]2[Pd(RaaiMe)Cl2]). The bases 2-MePy (d), 2,6-Me2Py (e) and 2,4,6-Me3Py (f) exhibits a bi-phasic reaction and follows the rate laws: rate–1 = (a + k[RPy][Pd(RaaiMe)Cl2]) and rate–2 = (a + k[RPy][Pd(RaaiMe)-Cl2]), where k is the third-order rate constant; k is the second-order first phase rate constant, k is the second-order second phase rate constant and a/a/a correspond to the solvent dependent constant of the respective reaction path. The rate data supports a nucleophilic association path. External addition of Cl– (LiCl) suppresses the rate, which follows the order: k/k/k (3) > k/k,k (1) > k/k,k (2). The k values are linearly related to the Hammett constants. The 2-substituted pyridines (d–f) remarkably reduce the rate and show a bi-phasic reaction behaviour as compared with 4-Rpy (a–c). This is attributed to the steric effect that destabilises the transition state. The rate decreases with increasing steric crowding at the ortho-position and follows the order: (d) > (f) > (e). The 4-substituted pyridines control the rate via an inductive effect and follow the order: (b) > (a) > (c). 相似文献
11.
The title reaction proceeds smoothly in MeOH-H2O togive the salts [RuCl(P)L2](ClO4), H2O (1, 2) or [Ru(PP)L2](ClO4)2, H2O (3, 4) where L=N(1)-benzyl-2-(arylazo)imidazole, P=PPh3, or PPh2Me, and PP=Ph2P(CH2)2PPh2 (dppe) or Ph2P(CH2)3PPh2(dppp). The complexes have been characterised by physico-chemical and spectroscopic methods. 相似文献
12.
Trans-dichloro-bis[N(1)-methyl-2-(arylazo)imidazol e] ruthenium(II) (tcc-Ru(MeL)2Cl2) reacts with tertiary phosphines giving rise to species of type [RuCl(P)-(MeL)2]+ and [Ru(P-P)(MeL)2]2+ in which Cl, P and P-P respectively occupy cis-positions [P=PPh3, or PPh2Me; P-P=Ph2P(CH2)2PPh2 (dppe) or Ph2P (CH2)3PPh2 (dppp)]. The cations have been isolated as perchlorates. The complexes display allowed t2(Ru) *(MeL) transitions in the visible region and show the energy ordering [RuCl(P)(MeL)2]+<[Ru(P-P) (MeL)2]2+. The RuIII/II couple occurs at high potentials, >1.1 V versus s.c.e. The azo reduction is sensitive to the nature of substituents in the ligand. The 1H n.m.r. spectra of the complexes are compatible with the isomer of C1-symmetry. 相似文献
13.
The nucleophilic substitution reaction of S2O32− with [Ru(HaaiR′)2(OH2)2](ClO4)2 (1) [HaaiR′ = 1-alkyl-2-(phenylazo)imidazole] and [Ru(ClaaiR′)2(OH2)2](ClO4)2 (2) [ClaaiR′ = 1-alkyl-2-(chlorophenylazo)imidazole] [where R′ = Me(a), Et(b) or Bz(c)] in acetonitrile–water (50% v/v) medium to yield Na2[Ru(HaaiR′)2(S2O3)2] (3a, 3b or 3c) and Na2[Ru(ClaaiR′)2(S2O3)2] (4a, 4b or 4c) has been studied. The products were characterized by microanalytical data and spectroscopic techniques (UV–Vis, NMR and mass spectroscopy). The reaction proceeds in two consecutive steps (A → B → C); each step follows first order kinetics with respect to each complex and S2O32−, and the first step second order rate constant (k′2) is greater than the second step one (k″2). An increase in the π-acidity of the ligand increases the rate. Thermodynamic parameters, the standard enthalpy of activation (Δ‡H0) and the standard entropy of activation (Δ‡S0), have been calculated for both steps using the Eyring equation from variable temperature kinetic studies. The low Δ‡H0 and large negative Δ‡S0 values indicate an associative mode of activation for both aqua ligand substitution processes. 相似文献
14.
N(1)-Ethyl-2-(arylazo)imidazoles (L) react with RuCl3 giving green (5) and blue RuL2Cl2 (6) isomers. The green isomer is quantitatively transformed into the blue isomer on boiling under reflux in 1,2-dichlorobenzene. The ligand is of the N,N-chelating type and in principle, provides five geometrical isomers. Considering the coordination pairs in the order: Cl, N(imidazole), N and N(azo),N the green isomer isspectroscopically characterised as trans-cis-cis-tcc-RuL2Cl2 (5) and the blue isomer is cis-trans-cis-ctc-RuL2Cl2 (6). The green isomer reacts smoothly with tertiary phosphines giving species of type [RuCl(P)L2]+ (7,8) and [Ru(P-P)L2]+2 (9,10) in which Cl, P and P-P respectively occupy cis-positions [P = PPh3, PPh2Me, P-P = Ph2P(CH2)2PPh2 (dppe) and Ph2P(CH2)3PPh2 (dppp)]. All the complexes display allowed t2(Ru) * (L) transitions in the visible region. A systematic shift of this MLCT band to higher energy occurs in the order: tcc-RuL2Cl2 (5) < ctc-RuL2Cl2 (6) < [RuCl(P)L2]+ (7,8) < [Ru- (PP)L2]+2 (9,10). The RuIII/RuII couple (E0
M) occurs 0.6–0.8V in green tcc-RuL2Cl2 (5), 0.7–0.9V in blue ctc-RuL2Cl2 (6) and the high potentials observed (> 1.2V versus s.c.e.) in phosphine derivatives (7–10). The azo reduction (E0
L) appears at negative values with respect to s.c.e. and is found to be sensitive to substitution in the phenyl ring of the ligand frame. The potential difference (E0
M–E0
L) is linearly related to the MLCT band energies (CT) of green and blue RuL2Cl2 complexes. The phosphine derivatives behave differently, a linear correlation being observed between CT and E0
M. The isomer configuration of RuL2Cl2 and the stereochemistries of the phosphine derivatives are established by 1H n.m.r. spectral data. The green (5) and blue (6) isomers exhibit single -Me or -OMe signals indicatives of C2-symmetry. The phosphine complexes [Ru(P)Cl(L2)2]+/[Ru(P-P)(L2)2]+2 show two equally intense methyl signals suggesting C1-symmetry in the derivatives. 相似文献
15.
Sanjay Senapoti Kamal Krishna Sarker Tapan Kumar Mondal Chittaranjan Sinha 《Transition Metal Chemistry》2006,31(3):293-298
2-(Methyl)-4-(arylazo)imidazole (RLH) (1, 2) are new series of azoimidazoles. Upon treatment of alkylhalide in dry THF in presence of NaH has synthesised 1-alkyl-2-(methyl)-4-(arylazo)imidazole
(RLR′) (3, 4). They belong to the azoimine family of N,N′-chelating ligand. They stabilize the Cu(I) oxidation state and we have synthesized [Cu(RLR′)2](ClO4) (5, 6). These complexes show a moderately intense visible band (500–600 nm) which has been assigned to 3d(Cu) → π*(ligand) transition. Ag(I) complexes of RLR′ (7, 8) are also very stable under ambient conditions and show weak transitions in the visible region. The Cu(I)-complexes show high
potential Cu(II)/Cu(I) redox couple > 0.4 V vs Ag, AgCl/Cl− reference electrode. All these complexes have been structurally characterized by 1H NMR spectroscopic data. 相似文献
16.
Nucleophilic substitution of Pd(RaaiR′)Cl2 [(RaaiR′ = 1-alkyl-2-(arylazo)imidazole, p-R-C6H4-N=N-C3H2NN-1-R′; where R = H(a)/ Me(b)/ Cl(c) and R′ = Et(1)/Bz(2)] with 2-Mercaptopyridine (2-SH-Py) in acetonitrile (MeCN) at 298 K, to form [Pd2(2-S-Py)4], has been studied spectrophotometrically under pseudo-first-order conditions and the analyses support the nucleophilic association
path. The reaction follows the rate law, Rate = {k
0 + k [2-SH-Py]
0
2
}[Pd(RaaiR′)Cl2]: first order in Pd(RaaiR′)Cl2 and second order in 2-SH-Py. The rate of the reaction follows the order: Pd(RaaiEt)Cl2
(1) < Pd(RaaiBz)Cl2
(2) and Pd(MeaaiR′)Cl2 (b) < Pd(HaaiR′)Cl2 (a) < Pd(ClaaiR′)Cl2 (c). External addition of Cl− (LiCl) and HCl suppresses the rate (Rate ∝ 1/[Cl−]0 & ∝1/[HCl]0). The reactions have been studied at different temperatures (293–308 K) and activation parameters (Δ‡ H° and Δ ‡ S°) of the reactions were calculated from the Eyring plot and support the proposed mechanism. 相似文献
17.
[Ni(NaiR)2(X)2] (X = N3 (3, 4) and NCS (5, 6) complexes are synthesized from the reaction of Ni(ClO4)2 · 6H2O with 1-alkyl-2-(naphthyl-α/β-azo)imidazole (α/β-NaiR) and sodium azide (NaN3) or ammonium thiocyanate (NH4NCS) (1:2:2 molar ratio) in methanol solution. The complexes are characterized by elemental, spectroscopic and magnetic study. The distorted octahedral structure has been confirmed by single crystal X-ray diffraction study of [Ni(β-NaiEt)2(NCS)2] (6b). Cyclic voltammogram exhibits quasireversible oxidation response at 0.3–0.4 V which is corresponding to Ni(III)/Ni(II) couple along with ligand reductions at negative potential to SCE reference electrode. 相似文献
18.
《Journal of Coordination Chemistry》2012,65(4):552-563
Reaction of Ni(ClO4)2 · 6H2O with 1-alkyl-2-(arylazo)imidazole (RaaiR/) and sodium azide (NaN3) or ammonium thiocyanate (NH4SCN) (1 : 2 : 2 molar ratio) in methanol gives [Ni(RaaiR/)2(X)2] (X=N3 (3, 4) and SCN (5, 6). All these complexes are characterized by elemental analyses, UV–Vis and IR spectral data, thermal and magnetic moment measurements. The X-ray structure is confirmed by single crystal measurement of [Ni(Pai-Me)2(N3)2] (3a). Cyclic voltammetry exhibits quasireversible response at >0.80 V corresponding to Ni(III)/Ni(II) couple along with ligand reductions at negative potential (<?0.5 V) to SCE reference. The electronic structure, spectral and redox properties are explained by DFT (Gaussian03) calculation. 相似文献
19.
20.
Arylazoimidazoles (2) are N,N-chelating ligands. The polymerization trend of the azolate system is restricted via N(1)-benzylation. The parent molecules (2), N(1)-benzylated products (3) and palladium complexes (4) were made by standard methods. The ligands (3) and complexes (4) are new. They have been characterized by elemental analysis, i.r., u.v.-vis. and high resolution 1H-n.m.r. spectral data. Redox studies were carried out by cyclic voltammetry. On complexation, azo reduction is shifted anodically. 相似文献