Paramagnetic organometallics formed by o-metallation of phenolic Schiff bases by ruthenium(III)

Ghosh, Prasanta; Pramanik, Arindam; Bag, Nilkamal; Lahiri, Goutam Kumar; Chakravorty, Animesh

doi:10.1016/0022-328x(93)83246-r

Cited by 53 publications

(59 citation statements)

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“…Here the difference in potential between the two successive reduction processes is found to be ;1.4 V ( Table 4) which is in good agreement with the earlier observed potential differences (1.3-1.4 V) between the two successive reduction processes Ru IV/III -Ru III/II in other complexes [53][54][55].…”

Section: E 298 C Nsq/q9supporting

confidence: 91%

Ruthenium dithiophosphates: synthesis, X-ray crystal structure, spectroscopic and electrochemical properties

et al. 2000

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The reactions of ammonium salts of dialkyldithiophosphate ligands, (RO) 2 PS 2 y NH 4 q (RsMe/Et), with Ru III Cl 3 P3H 2 O in methanol solvent and under N 2 atmosphere result in one-electron paramagnetic tris complexes {(RO) 2 PS 2 } 3 Ru III (1) in the solid state. The molecular structures of both complexes were determined by single-crystal X-ray diffraction. This shows the expected pseudo-octahedral geometry with reasonable strain due to the presence of a four-membered chelate ring. The reflectance spectra of the solid complexes display two bands in the range 596-476 nm and in the solid state the complexes exhibit one isotropic EPR signal at 77 K. Although the complexes 1 are stable in the solid state, in solution the complexes are transformed selectively into the diamagnetic and electrically non-conducting sulfur-bridged dimetallic species [{(RO) 2 PS 2 } 2 Ru IV (m-S) 2 Ru IV {S 2 P(OR) 2 } 2 ]. The formation of dimeric species in the solution state is authenticated by the electrospray mass spectrum of one representative complex where RsEt (1b). In dichloromethane solution the complexes show two moderately strong sulfur to ruthenium charge-transfer transitions in the range 514-419 nm, and two strong ligand based transitions in the UV region. The complexes exhibit two successive reversible reductions in the ranges 1.01™0.91 V and y0.44™y0.49 V versus SCE corresponding to Ru IV -Ru IV /Ru III -Ru III and Ru III -Ru III /Ru II -Ru II couples respectively. Electrochemically or chemically generated first step reduced complexes [{(RO) 2 PS 2 } 2 Ru III (m-S) 2 Ru III {S 2 P(OR) 2 } 2 ] 2y display two ligand to metal charge-transfer transitions in the visible region and in the complexes the two one-electron paramagnetic metal centers (low-spin Ru III , ,Ss1/2)are antiferromagnetically coupled. t 2gThe second step reduced species [{(RO) 2 PS 2 } 2 Ru II (m-S) 2 Ru II {S 2 P(OR) 2 } 2 ] 4y are observed to be very unstable.

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Section: E 298 C Nsq/q9supporting

confidence: 91%

Ruthenium dithiophosphates: synthesis, X-ray crystal structure, spectroscopic and electrochemical properties

et al. 2000

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“…It has been found [3,10] that organometallic ruthenium complexes derived from type 1 ligands exhibit different colours from the change of substituents on the phenyl ring containing an aldehyde function. Complex 1 afforded two charge-transfer bands near 475 nm and 585 nm.…”

Section: Spectroscopic Studiesmentioning

confidence: 99%

“…The role of the electron-withdrawing -NO 2 group on the phenyl ring, ligated to the metal centre through a σ-aryl bond, will be discussed in the context of light-induced delivery of nitric oxide. [3] Complexes 1 and 2 (Scheme 2) were red-brown in colour and both complexes were isolated in good yield. They were highly soluble in dichloromethane and benzene but were much less soluble in polar solvents like water and methanol.…”

Section: Introductionmentioning

confidence: 98%

“…It has been found that in the case of ruthenium(III) cyclometalates derived from Schiff-base ligands, the metal-carbon bond is established through orthometallation with the phenyl ring that has an aldehyde functional group, see Scheme 1 (A), X = CH, Type 1. [3] On the other hand, there is another group of structurally similar complexes where instead of azomethine nitrogen, the azo function is bound to the Ru III centre. In these types of complexes, orthometallation is observed with the ring that has been contributed by the aromatic amine during the azo coupling reaction, as shown in Scheme 1 (A), X = N, Type 2.…”

Section: Introductionmentioning

confidence: 99%

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Ruthenium(III) Cyclometalates Obtained by Site‐Specific Orthometallation and Their Reactivity with Nitric Oxide: Photoinduced Release and Estimation of NO Liberated from the Ruthenium Nitrosyl Complexes

Ghosh

Kumar

2012

Eur J Inorg Chem

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Cyclometalated RuIII complexes [Ru(LSB1)(PPh3)2Cl] (1), [LSB1H2 = 2‐(3‐nitrobenzylideneamino)phenol], and [Ru(LSB2)(PPh3)2Cl] (2), [LSB2H2 = 4‐methyl‐2‐(3‐nitrobenzylideneamino)phenol and H = dissociable protons], were synthesized by site‐specific orthometallation and characterized by spectroscopic and electrochemical studies. Complexes 1 and 2 were treated with in situ generated nitric oxide (NO), derived from an acidified nitrite solution, which afforded the ruthenium nitrosyl complexes [Ru(LSB3H)(PPh3)2(NO)Cl](ClO4) (1a) and [Ru(LBOX)(PPh3)2(NO)Cl](ClO4) (2a), respectively, [LSB3H2 = 4‐nitro‐2‐(3‐nitrobenzylideneamino)phenol, LBOXH = 5‐methyl‐7‐nitro‐2‐(3‐nitrophenyl)benzoxazole and H = dissociable protons]. Complexes 1a and 2a were found to be diamagnetic and were characterized by 1H NMR and 31P NMR spectral studies. Both 1a and 2a exhibited νNO in the range 1800–1835 cm–1 in the IR spectra. Molecular structures of σ‐aryl ruthenium nitrosyl complexes 1a·CH3OH·2CH2Cl2·H2O and 2a·2CH2Cl2 were determined by X‐ray crystallography. Nitrosylation at the metal centre, oxidative cyclization and ligand nitration were authenticated from the crystal structures. The redox properties of the metal centre were investigated. In both the nitrosyl complexes 1a and 2a, coordinated NO was found to be photolabile. The amount of photoreleased NO was estimated by using the Griess reagent and the data was compared with that obtained from sodium nitroprusside (SNP). The role of the nitro group in the ligand frame was discussed with regard to orthometallation, NO reactivity and photolability.

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“…The solutions are EPR-active when frozen into the glassy state (dichloromethane/toluene, 77 K), giving rise to well-resolved rhombic spectra that are consistent with a low-spin 4d 5 configuration in a nonaxial geometry. [35,36] A representative spectrum (Figure 4) and the g values (Table 3) are given here. …”

Section: Electrochemistry: Metal Oxidationmentioning

confidence: 99%

Synthesis, Structure, and Properties of Biimidazole‐Chelated Arylruthenium Complexes

2003

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By reacting Ru(η2‐RL)(PPh3)2(CO)Cl (1) with excess 4,5‐dimethyl‐2,2′‐biimidazole (dmbi), organometallics of the type [Ru(η1‐RL)(PPh3)2(CO)(dmbi)](PF6) (2) have been isolated in excellent yield (η2‐RL is C6H2O‐2‐CHNHC6H4R(p)‐3‐Me‐5, η1‐RL is C6H2OH‐2‐CHNC6H4R(p)‐3‐Me‐5 and R is Me, OMe and Cl). In this process the dmbi ligand undergoes five‐membered chelation, the iminium‐phenolato function tautomerizes to the imine‐phenol function and the Schiff base performs a large rotation around the Ru−C bond. The crystal and molecular structure of [Ru(η1‐MeL)(PPh3)2(CO)(dmbi)](PF6)·CH2Cl2 is reported. For steric reasons the carbon monoxide ligand is located syn to the phenolic oxygen atom as opposed to anti in the precursor 1. In the hydrogen bonded imine‐phenol function the O−H, H···N, and N···O distances are 0.83(8), 1.77(8), and 2.552(6) Å, respectively, the O−H···N angle being 156(2)°. The Ru(dmbi) chelate along with the metallated carbon atom and the CO ligand define an equatorial plane from which the metallated aldimine fragment is rotated by 34.5° due to interligand repulsion. This results in two unequal [2.348(2) and 2.411(2) Å] Ru−P bonds and an apparent suppression of the trans influence of the metallated carbanionic site. The cation and anion in the complex are engaged in N−H···F and C−H···F hydrogen bonding, generating a centrosymmetric dimer in the lattice. One of the hydrogen bonds, characterized by H···F, 2.03(8) Å and N−H···F, 166(2)°, is particularly strong. Solutions of 2 absorb near 400 nm and emit near 460 nm with quantum yields and lifetimes of ca. 10−3 and ⩽ 20 ns, respectively. The emission, which probably involves the 3MLCT state incorporating a π*(dmbi) contribution, is peculiar to the coligation of η1‐RL and dmbi to bivalent ruthenium. In dichloromethane solution 2 displays a quasireversible 2+/2 couple near 0.70 V vs. SCE [2+ is the ruthenium(III) analogue of 2]. Coulometrically generated solutions of 2+ display a strong absorption near 400 nm and rhombic EPR spectra with g values near 2.55, 2.15, and 1.83. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Paramagnetic organometallics formed by o-metallation of phenolic Schiff bases by ruthenium(III)

Cited by 53 publications

References 24 publications

Ruthenium dithiophosphates: synthesis, X-ray crystal structure, spectroscopic and electrochemical properties

Ruthenium dithiophosphates: synthesis, X-ray crystal structure, spectroscopic and electrochemical properties

Ruthenium(III) Cyclometalates Obtained by Site‐Specific Orthometallation and Their Reactivity with Nitric Oxide: Photoinduced Release and Estimation of NO Liberated from the Ruthenium Nitrosyl Complexes

Synthesis, Structure, and Properties of Biimidazole‐Chelated Arylruthenium Complexes

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