Chemistry of Ruthenium Polypyridine Complexes: VI. Synthesis and Photochemistry of cis-[Ru(bpy)2(bipy)X]q Complexes

Complexes cis-[Ru(bpy)₂(bipy)(X)] ^{n +} [bpy = 2,2'-bipyridyl, bipy = 4,4'-bipyridyl, X = Br^-, ONO^-, CN^- (n = 1); MeCN, PPh₃ (n = 2), and NO⁺ (n = 3)] were synthesized. Irradiation of acetonitrile solutions of the complexes with X = Cl^-, Br^-, ONO^-, NO₂-, CN^-, NH₃, MeCN, and PPh₃ by visible light results in photosubstitution of 4,4'-bipyridyl by a solvent molecule. The electronic absorption spectra of the complexes were assigned on the basis of quantum-chemical calculations. A correlation was revealed between photolysis quantum yields and charges transferred from ligands X upon their coordination.     

Chemistry of Ruthenium Polypyridine Complexes: IX. Nitro-Nitrosyl Equilibrium in cis-[Ru(2,2'-bpy)2(L)NO2]+ Complexes

Ruthenium(II) bisbipyridyl complexes cis-[Ru(bpy)₂(L)NO₂](BF₄) (bpy is 2,2'-bipyridyl) with 4-substituted pyridine ligands L = 4-(Y)py (Y = NH₂, Me, Ph, and CN) were obtained. The equilibrium constants of the reversible nitro-nitrosyl transition [Ru(bpy)₂(L)NO₂]⁺ + 2H⁺ [Ru(bpy)₂(L)NO]^{3 +} + H₂O were measured in solutions with pH 1.5-8.5 (ionic strength 0.4). The constants correlate with the protonation constants of free ligands 4-(Y)py.     

Structural Chemistry of Cu(I) Allyl and Acetylene π-Complexes

Stereospecific behavior of allyl derivatives and acetylenes in CuX -complexes (X = Cl^-, Br^-, NO₃ ^-, BF₄ ^-, 1/2SiF₆ ^2-, 1/2SO₄ ^2-) is studied by X-ray diffraction analysis. The influence of donor atoms N, S, and O and of the Cu-X bond polarization on the -complex formation is considered. The efficiency of Cu-(C=C) and Cu-(CC) -interaction and specific behavior of mono- and disubstituted acetylenes with respect to Cu(I) are compared.     

Reactions of Tertiary Alcohols with Palladium(II) Tetraaqua Complex. Formation of Palladium π-Allyl Complexes

Transformations of 2-methyl-2-propanol, 2-methyl-2-butanol, 2-methyl-2-pentanol, 1-methyl-1-cyclohexanol, and 1-ethyl-1-cyclohexanol in the presence of tetraaquapalladium(II) ions in perchloric acid madium were studied. It was found that the reactions give rise to palladium(II) -allyl complexes. The reaction rate increases and the yield of the corresponding -allyl complex decreases with increasing hydrocarbon chain length. Addition of iron(III) ions to the systems essentially increases the yield of palladium -allyl complexes. The olefin formed from the corresponding tertiary alcohol participates in the formation of the palladium -allyl complex. Oxidation of 2-methyl-2-butanol with tetraaquapalladium(II) ions gives the isomeric palladium -allyl complexes [Pd(³-(CH₃)₂CCHCH₂)bpy]ClO₄ and [Pd(³-(CH₂C(CH₃)CHCH₃))bpy]ClO₄, which were isolated using 2,2'-bipyridyl and characterized by ¹H and ¹³C NMR spectroscopy.     

Chemistry of Ruthenium Polypyridine Complexes: V. Electronic Structure of Ruthenium(II) Bipyridine-Diphosphine Mixed-Ligand Complexes

Comparative analysis of the donor-acceptor capacities of diphosphine ligands in two series of complexes: cis-[Ru(bpy)2(LL)]^{q +} [LL = 2,2'-bipyridine (bpy), o-benzoquinonediimine (bqdi), cis-1,2-bis(diphenylphosphino)ethane, cis-1,2-bis(diphenylphosphino)ethylene (dppen), (NH3)2, and (CO)2] and [Ru(NH₃)₄. (LL)]^{2 +} (LL = bpy, dppen, and bqdi), was performed. Diphosphines are the strongest donors; they compare in -acceptor capacity which is associated with phosphorus d orbitals with 2,2'-bipyridine and fall far short of o-benzoquinonediimine and carbonyl.     

Electronic Spectra of Ruthenium Nitrosyl Complexes with Macrocyclic Ligands

Electronic spectra of ruthenium(II) nitrosyl complexes [Ru(NO)(salen)(X)]⁴ⁿ (X = Cl, H₂O; n = 0, 1) and [Ru(NO)(P)(ONO)] with tetradentate -conjugated ligands N,N'-ethylenebis(salicylideniminato) dianion (salen) and porphinate dianion (P) were calculated by the TD DFT and CINDO/CI methods. The data obtained were compared to the results of previous calculations of the spectra of trans-[Ru(NO)(NH₃)₄(L)]^{3 +} complexes with nitrogen-containing heterocyclic ligands L. It was found that charge-transfer transitions to * orbitals of the RuNO group dominate in the long-wave part of the spectrum irrespective of the other ligands.     

Mixed-Ligand Ruthenium(II) Complexes as Structural Units of Polynuclear Systems

Spectral and kinetic parameters were studied for phosphine-bipyridyl ruthenium(II) complexes, namely, cis-[Ru(Bipy)₂(PPh₃)X](BF₄), cis-[Ru(Bipy)(Dppe)X₂], and cis-[Ru(Bipy)(Dppene)X₂] (where Bipy is 2,2"-bipyridyl, PPh₃is triphenylphosphine, Dppe is 1,2-bis(diphenylphosphino)ethane, and Dppene iscis-1,2-bis(diphenylphosphino)ethylene; X = CN^–, NO₂ ^–), in the frozen (77 K) alcohol glasses (EtOH–MeOH, 4 : 1). The energies of the singlet and triplet metal-to-ligand charge transfer states d(Ru) *(Bipy) were found to increase in the order [Ru(Bipy)₂X₂] < [Ru(Bipy)₂(PPh₃)X]⁺< [Ru(Bipy)(Dppe)X₂] < [Ru(Bipy)(Dppene)X₂]. The luminescence quantum yields and the rate constants of the nonradiative deactivation of the lowest excited state ³MLCT increase in the same order.     

Synthesis,Characterization, Electrochemical and Spectroscopic Properties of [Ru(dppt)(bpy)Cl]+ and [Ru(pta)(bpy)Cl]+

Two novel Ru^II complexes [Ru(dppt)(bpy)Cl]ClO₄ (1) and [Ru(pta)(bpy)Cl]ClO₄ (2)[dppt, pta and bpy = 3-(1,10-phenanthrolin-2-yl)-5,6-diphenyl-as-triazine, 3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6-f]acenaphthylene and 2,2-bipyridine, respectively] were synthesized and characterized by elemental analysis and electrospray mass spectrometry, ¹H-n.m.r., and u.v.–vis spectroscopy. The redox properties of the complexes were examined using cyclic voltammetry. Due to the strong -accepting character of asymmetric ligands, the MLCT bands of (1) and (2) are shifted significantly to lower energies by comparison with [Ru(tpy)(bpy)Cl]⁺.     

Calculation of two-center zero-field splitting integrals

Two-center zero-field splitting (ZFS) integrals have been calculated by numerical integration of Coulomb repulsion integrals which are evaluated over basic charge distributions as defined by Roothaan in terms of Slater atomic orbitals. The method is applied to the calculation of the ZFS integrals for -, - and - electron interactions on C, N and N⁺ centers. Numerical results are given.

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Zusammenfassung Zweizentren ZFS-Integrale sind mittels numerischer Integration von Coulombintegralen berechnet worden, und zwar die -, -- und --Integrale an C-, N- und N⁺-Zentren. Die numerischen Resultate werden mitgeteilt.

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Résumé Les intégrales bi-centriques de séparation à champ nul (ZFS) ont été calculées par intégration numérique des intégrales de répulsion coulombiennes évaluées pour les distributions de charge fondamentales définies par Roothan en termes d'orbitales atomiques de Slater. La méthode est appliquée au calcul des intégrales ZFS pour les interactions -, - et - sur les centres C, N et N⁺. Résultats numériques.

     

Synthesis,spectroscopy and electrochemistry of mixed-ligand complexes of platinum(II) and palladium(II)

Mixed-ligand complexes [MX₂(MBPY)] (M = Pd^II or Pt^II; X = Cl^–, I^–, N^– ₃ or NO₂ ^–; MBPY = 4,4-dimethyl-2,2-bipyridine) have been prepared and characterised by elemental analyses, conductivity measurements, i.r., electronic absorption and ¹H-n.m.r. spectroscopic techniques. The cyclic voltammograms of these complexes suggest the involvement of the metal d orbital in the one-electron oxidation process and the * orbital of the MBPY in the one-electron reduction process. [Pt(MBPY)(N₃)₂] shows solution-state luminescence at room temperature.     

Energetics of n-π* and π-π* charge-transfer complexes formed between amine donors and chloranil as π-electron acceptor

The heats of formation ofn- ^* and- ^* charge-transfer interactions have been computed from the charge-transfer spectra of molecular complexes formed in the pyridinechloranil and aniline-chloranil systems.

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Zusammenfassung Anhand der Charge-Transfer-Spektren von Molekülkomplexen aus Pyridin-Chloranil und Anilin-Chloranil wurde die Wärme für die Bildung vonn- ^* und -^* Charge-Transfer-Wechselwirkungen berechnet.

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Metastable States of Ruthenium Nitrosyl Complexes. Density Functional Quantum-Chemical Calculations

Geometry optimization for the ground state and metastable isomers of the nitrosyl complexes trans-[Ru(NO)(NH₃)₄(L)]^{3 +} (L = imidazole, pyridine, pyrazine, nicotinamide), [Ru(NO)(CN)₅]^{2 -}, and [Ru(NO)Cl₅]^{2 -} was performed in terms of the density functional theory (SVWN/LanL2DZ + 6-31G). The energy gap between the stable structure and the isomer with linear coordination of NO via the oxygen atom is practically independent of the nature of ligand L in the series of ammonia complexes with the same charge, and the energy gap between the stable structure and the isomer with side ² coordination of NO gets slightly smaller if ligand L possesses -acceptor properties.     

Synthesis of ferricinium bis[π-(3)-1,2-dicarbollyl]cobaltate(iii), [FeIII(η5-Cp)2]+{CoIII[π-(3)-1,2-B9C2H11]2}−

Ferricinium bis[-(3)-1,2-dicarbollyl]cobaltate(III), [Fe^III(⁵--Cp)₂]⁺{Co^III[-(3)-1,2-B₉C₂H₁₁]₂}^–, has been prepared by the reaction of Fe^III(⁵--Cp)₂]⁺ with the anion {Co^III[-(3)-1,2-B₉C₂H₁₁]₂}^–. It is a light-green amorphous precipitate that is stable as a dry solid up to 227 °C and unstable in solutions of acetonitrile and acetone.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 10, pp. 1810–1811, October, 1994.This work was supported by the Russian Foundation for Basic Research (Project No 93-03-5987).     

Acid-base properties of 1,2,5-oxadiazoles. 2. Aminofurazans

The behavior of 3-R-4-aminofurazans (R = NH₂, CH₃, OCH₃, N₃, COOH, and NO₂) in sulfuric acid solutions was studied by electronic and PMR spectroscopy. The constants of protonation (pK _aBH+) at the amino group and in the ring were calculated from the changes in the spectra. Dependences of the position of the absorption maxima corresponding to ^* transitions and the pK _aBH+ values and with the ^o substituent constants were found.See [1] for Communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 321–324, March, 1981.     

Linkage isomerism and redox properties of ruthenium–polypyridine benzotriazole complexes

A new series of mono- and di-substituted ruthenium–polypyridine complexes of the type cis-[Ru^III,II (bpy)₂(L1)(L2)] ^{n +} (L1 = Cl^–, bta or py; L2 = bta; bpy = 2,2-bipyridine; bta = benzotriazole; py = pyridine) has been prepared, isolated as hexafluorophosphate salts, and investigated in organic solutions by means of cyclic voltammetry and spectroelectrochemistry. The chemical oxidation of all the benzotriazole derivatives, starting from cis-[Ru^II(bpy)₂(L1)(bta)] ^x (x = +1 or +2), leads essentially to N(3)-bound products, i.e., cis-[Ru^III(bpy)₂ (L1)(N(3){bta})] ^x+1 isomers. Nevertheless, while the benzotriazole-monosubstituted species undergoes an intramolecular isomerization, N(3) N(2), accompanying the electrochemical reduction centered on the metal ion, Ru^III Ru^II, the disubstituted derivatives do not display any spectral or electrochemical evidence of linkage isomerism. The equilibrium and kinetic constants for the isomerization were determined from the cyclic voltammograms at several scan rates, according to an electrochemical–chemical (EC) coupling scheme. The data were compared with a set of constants and parameters obtained previously for a series of ruthenium and iron complexes. The experimental results were found to be quite consistent with theoretical calculations, and reflect the importance of -backbonding interactions in the stabilization of the metal-centered reduced state (M^II) on such species with low-spin d⁶ configuration.     

π -Type and σ -type cation- π complexes of atomic cations

MP2/6-31+G* calculations were performed on the cation- complexes of ethylene, cyclobutadiene and benzene with a number of atomic cations. It was found that except B⁺ all the atomic cations form -type cation- complexes with ethylene. On the other hand, with cyclobutadiene Li⁺, N⁺, Na⁺, P⁺ and K⁺ form -type complexes, whereas H⁺, F⁺, and Cl⁺ form covalent -type complexes. With benzene Li⁺, B⁺, Na⁺, Al⁺, and K⁺ form -type complexes whereas H⁺, F⁺, and Cl⁺ form -type complexes. It was concluded that the driving force to form the -type complex is chemical bonding, and that for metal cations to form -type complexes is non-covalent interaction.     

On the excited states ofp-quinones and an interpretation of the photocycloaddition ofp-quinones to alkenes

A theoretical investigation is made of the electronic states ofp-benzoquinone (PBQ), methyl substituted PBQ's and 1,4-naphthoquinone (NQ). In accord with experiment, the lowest triplet state of PBQ is calculated to be³ B _1g (n, *), while that for duroquinone (DQ) is³ B _3g (, *). The electron densities of these states are consistent with the hypothesis that³ n, * states lead to oxetan formation and³, * states to cyclobutanes. It is predicted that trimethyl PBQ might form both adducts, as the two states are calculated to be nearly degenerate.The photochemistry of NQ is more complex. The lowest excited triplet state is calculated to be ofn, * symmetry, in accord with experiment; however, several other states are predicted near in energy, and the photochemistry cannot be rationalized unambiguously.This work was supported in part by the National Research Council of Canada.     

Infrared spectra of vinyl compounds and the effects of conjugation involving the π-electrons of the vinyl group

Conclusions The frequencies of the =CH₂ group wagging vibration in CH₂=CH-X compounds reflects both the inductive effect of the substituents X, and the effects of, -, ,p- and (d-p)-conjugation in which these substituents take part.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.l, pp. 152–154, January 1970.     

Thermochemistry of some π-π charge transfer complexes formed between methylbenzene donors and π-electron acceptors

The heats of formation for- ^* charge transfer interactions have been computed from the charge transfer spectra of molecular complexes formed between methylbenzene donors and-electron acceptors.Miss Rajni Sachdeva and Anita Singla are grateful to I.C.A.R. (India) and C. S. I. R. (India), respectively, for financial assistance.