The synthesis and structure of the [2.2]paracyclophane cluster Ru6C(CO)13(μ 3-η 2:η 2:η 2-C16H16)(PPh3) and a study of the 1H-n.m.r. spectra of [2.2]paracyclophane and benzene clusters

Summary The [2.2]paracyclophane cluster, Ru₆C(CO)₁₄( ₃- ^{2 2 2}-C₁₆H₁₆) (1), undergoes reaction with Me₃NO and triphenylphosphine to yield Ru₆C(CO)₁₃( ₃- ^{2 2 2}-C₁₆H₁₆)(PPh₃) (2), which may also be produced from (1) by thermolysis with PPh₃ in THF. Compound (2) has been fully characterized in solution by spectroscopy and in the solid state by a single crystal X-ray diffraction analysis at 277 K, and its structure is compared with that of the parent cluster, (1). Using the same synthetic procedures, the tricyclohexylphosphine analogue, Ru₆C(CO)₁₃( ₃- ^{2 2 2}-C₁₆H₁₆)(PCy₃) (3), has also been prepared and characterized spectroscopically. A comparison of the chemical shifts of the 577-01 protons in the ¹H-n.m.r. spectra of compounds (1)–(3) together with a variety of other [2.2]paracyclophane and benzene clusters has been made.     

Solvatochromism of Heteroaromatic Compounds: XIX. Factors Affecting Quantitative Characteristics of Solvatochromism in Aprotic Inert Media

The effects of aprotic inert media on the electronic absorption spectra of aromatic nitro compounds p-NO₂C₆H₄R were used as evidence for the linear correlation between the slope s _a of the solvatochromism equations _max = ₀ + s _a^* and the dipole moments of the molecules in their ground electronic state _g. A linear correlation was established between 0 and the first ionization potential of subunits C₆H₅R. A new approach to estimating the dipole moment of electronically excited molecules (_e) for molecules like p-NO₂C₆H₄R on the basis of the correlation _e = r_g was proposed.     

Electron density distribution in vanadocene (η5-C5H5)2V and mixed metallocenes (η5-C5H5)M(η5-C7H7) (M = Ti,V, or Cr) and (η5-C5H5)Ti(η8-C8H8). Effect of the nature of the cyclic ligand on the character of the M--(π-ligand) bond

The electron density distribution and atomic displacements were analyzed based on the results of precision low-temperature X-ray diffraction studies of a series of isostructural (Pnma, Z = 4) mixed metallocenes (⁵-C₅H₅)M(⁵-C₇H₇) (M = Ti, V, or Cr) and (⁵-C₅H₅)Ti(⁸-C₈H₈). The barriers to rotation of the cyclic ligands were evaluated based on rms libration amplitudes. Analysis of the deformation electron density demonstrated that the character of the M--(-ligand) chemical bond depends substantially both on the nature of the metal atom and the size of the ligand. Lowering of the local symmetry of the (⁵-C₅H₅)M(⁵-C₇H₇) complexes to C_S leads to distortion of the cylindrical symmetry of the electron density distribution observed in vanadocene (⁵-C₅H₅)₂V and titanocene (⁵-C₅H₅)Ti(⁸-C₈H₈).     

19-Electron arenecyclopentadienyl complexes of ruthenium

A series of are necyc lope ntadienyl complexes,i. e., [Ru(⁵-c₅R₅)(⁶- are ne)]⁺ (1, R= H, arene = C₆H₆; 2, R = Me, arme = C₆H₆; 3, R = H, arctic = C₆H₃Me₃; 4, R = Me, arene = C₆H₃Me₃; 5, R = H, arene = C₆Me₆; 6, R = Me, arene = C₆Me₆) was studied by cyclic voltammetry. These compounds are capable of both oxidation and reduction. The reduction potential values depend on the number of methyl groups in the complex. Reduction of benzene complexes I and 2 by sodium amalgam in THF leads to the formation of decomplexation products, the addition of hydrogen to benzene, and dimerization of the benzene ligands. Both chemical and electrochemical reductions of mesitylene complexes3 and4 result in dimeric products [(⁵-C₅R₅)Ru(-⁵;⁵-Me₃H₃C₆H₃Me₃)Ru(⁵-C₅R₅)] (14, R = H; 15, R = Me). The action of sodium amalgam on compound5 gives products of hydrogen addition to both hexamethylbenzene (17) and cyclopentadienyl (18) ligands along with the major product, the dimer [⁵-C₅H₅)Ru(-⁵; ⁵-Me₆C₆C₆Me₆)Ru(⁵-C₅H₅)] (16). In contrast to5, its permcthylated analog 6 is only capable of adding hydrogen to the hexamethylbenzene ligand.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1691–1697, July, 1996.     

Viscosities of solutions of electrolytes and nonelectrolytes inN-methylacetamide at 35° and 55°C

The viscosities of dilute solutions of a number of tetraalkylammonium and alkali metal halides, tetraphenylarsonium chloride, sodium tetraphenylborate, and tetrabutylammonium tetrabutylborate, as well as several nonelectrolytes have been measured in the high dielectric constant solvent N-methylacetamide (NMA) at 35 and 55°C. The relative viscosities were fitted to the extended Jones-Dole equation, = 1 + AC^1/2 + BC + DC². The pattern of behavior of the B coefficients is roughly similar to that observed in H₂O. However, the small ions have exceptionally large B values in this solvent due to strong solvation effects, while the large organic ions do not display the sharp crossing of the Einstein law, B=2.5 _V, characteristic in H₂O of hydrophobic interaction. The D coefficients roughly parallel the B behavior and display remarkably regular ionic trends. This suggests that they arise largely from hydrodynamic origins. Nonelectrolytes have small or negative B coefficients showing that the Einstein law is not applicable at the molecular level and that nonelectrolytes are poor models for structurally similar ions. A simple mixture law is presented as an alternative to the Einstein law to explain the B coefficients.     

Synthesis and spectroscopic studies of complexes containing the Schiff base 1-acetylferrocene(thio)semicarbazone

Summary [RuCl₂(CO)₂] _n reacts with the Schiff base 1-acetylferrocenethiosemicarbazone, [Fe(-Cp)(-C₅H₄MeC=NN-HCSNH₂)] to give [Fe(-Cp)(-C₅H₄MeC=NN-HCSNH₂)RuCl₂(CO)₂] and with 1-acetylferrocenesemicarbazone [Fe(-Cp)(-C₅H₄MeC=NN-HCSNH₂)] to give [Fe(-Cp)(-C₅H₄MeC=NN-HCSNH₂)RuCl₂-(CO) ₂]. Spectroscopic data indicate that the Schiff bases act as bidentate ligands and coordinate to ruthenium via the hydrazinic N and either the S or O atoms, respectively, giving stable heterobimetallic complexes, which have been characterized by i.r. and ¹H-n.m.r. spectroscopies, and elemental analyses.Part of this work was presented at the First International Conference in Chemistry and its applications in Doha, Qatar, 1993.     

Investigation of the redox properties of polynuclear “ladder” complexes containing Cr,Mn, and Fe

The redox potentials of new Cr, Mn, and Fe polynuclear ladder complexes, (⁵-Cp)Fe(CO)₂(¹,⁵-C₅H₄)Fe(CO)₂(¹,⁵-C₅H₄)Mn(CO)₃, (⁵-Cp)Fe(CO)₂(¹,⁵-C₅H₄)Mn(CO)₃, (⁵-Cp)Fe(CO)₂(¹,⁶-Ph)Cr(CO)₃, (⁵-Cp)Fe(CO)₂(¹,⁵-C₅H₄)Fe(CO)₂CH₂Ph, (⁵-Cp)Fe(CO)₂(¹,⁶-CH₂Ph)Cr(CO)₃, were measured and the mechanism of their electrochemical oxidation and reduction was suggested. It was shown that the - or -bonds of the bridging ligand can be cleaved selectively by applying cathodic or anodic potentials, respectively. On the basis of the obtained electrochemical data, a mechanism is suggested for the rearrangement observed when the complexes are metallated by butyllithium.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 362–366, February, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No 94-03-08628a).     

Comparison of the Bonding of Benzene and C60 to a Metal Cluster: Ru3(CO)9(μ3-η2,η 2,η2-C6H6) and Ru3(CO)9(μ3-η2,η2,η2-C60)

The electron distributions and bonding in Ru₃(CO)₉( ³- ², ², ²-C₆H₆) and Ru₃(CO)₉( ³- ², ², ²-C₆₀) are examined via electronic structure calculations in order to compare the nature of ligation of benzene and buckminsterfullerene to the common Ru₃(CO)₉ inorganic cluster. A fragment orbital approach, which is aided by the relatively high symmetry that these molecules possess, reveals important features of the electronic structures of these two systems. Reported crystal structures show that both benzene and C₆₀ are geometrically distorted when bound to the metal cluster fragment, and our ab initio calculations indicate that the energies of these distortions are similar. The experimental Ru–C_fullerene bond lengths are shorter than the corresponding Ru–C_benzene distances and the Ru–Ru bond lengths are longer in the fullerene-bound cluster than for the benzene-ligated cluster. Also, the carbonyl stretching frequencies are slightly higher for Ru₃(CO)₉( ³- ², ², ²-C₆₀) than for Ru₃(CO)₉( ³- ², ², ²-C₆H₆). As a whole, these observations suggest that electron density is being pulled away from the metal centers and CO ligands to form stronger Ru–C_fullerene than Ru–C_benzene bonds. Fenske-Hall molecular orbital calculations show that an important interaction is donation of electron density in the metal–metal bonds to empty orbitals of C₆₀ and C₆H₆. Bonds to the metal cluster that result from this interaction are the second highest occupied orbitals of both systems. A larger amount of density is donated to C₆₀ than to C₆H₆, thus accounting for the longer metal–metal bonds in the fullerene-bound cluster. The principal metal–arene bonding modes are the same in both systems, but the more band-like electronic structure of the fullerene (i.e., the greater number density of donor and acceptor orbitals in a given energy region) as compared to C₆H₆ permits a greater degree of electron flow and stronger bonding between the Ru₃(CO)₉ and C₆₀ fragments. Of significance to the reduction chemistry of M₃(CO)₉( ³- ², ², ²-C₆₀) molecules, the HOMO is largely localized on the metal–carbonyl fragment and the LUMO is largely localized on the C₆₀ portion of the molecule. The localized C₆₀ character of the LUMO is consistent with the similarity of the first two reductions of this class of molecules to the first two reductions of free C₆₀. The set of orbitals above the LUMO shows partial delocalization (in an antibonding sense) to the metal fragment, thus accounting for the relative ease of the third reduction of this class of molecules compared to the third reduction of free C₆₀.     

Synthesis of cationic indenyl- and fluorenyl-arene complexes of ruthenium

Interaction of [Ru(-C ₆ H ₆ )Cl ₂ ] ₂ with indenyl- or fluorenyllithium in THF gives, together with cationic benzene complexes [Ru( ⁵ -C ₉ H ₇ )(-C ₆ H ₆ )]⁺ and [Ru( ⁵ -C ₁₃ H ₉ )(-C ₆ H ₆ )]⁺, the neutral cyclohexadienyl derivatives Ru( ⁵ -C ₉ H ₆ -C ₉ H ₇ ) and Ru( ⁵ -C ₁₃ H ₉ )( ⁵ -C ₆ H ₆ -C ₁₃ H ₉ ), respectively. Interaction of the cyclohexadienyl complexes with Al ₂ O ₃ , Ph ₃ C⁺, and CF ₃ CO ₂ H has been studied. Reaction of Ru( ⁵ -C ₁₃ H ₉ )( ⁵ -C ₆ H ₇ ) with CF ₃ CO ₂ H in the presence of an arene yields cationic cyclohexadienylarene complexes: [Ru( ⁵ -C ₁₃ H ₉ )( ⁶ -arene)]⁺ (arene=C ₆ H ₆ or 1,3,5-Me ₃ C ₆ H ₃ ).A. N. Nesmeyanov Institute of Organoelemental Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 699–706, March, 1992.     

Ruthenium clusters containing the [2.2] paracyclophane ligand: Recent developments in arene-cluster chemistry

In this article we review the synthesis, reactivity, and characterization of a number of clusters bearing the [2.2] paracyclophane ligand with nuclearities ranging from two to eight. Particular attention is focused on the different coordination modes that paracyclophane adopts; these being µ₁- ⁶, µ₂- ³ : ³, µ₃- ¹ : ² : ², and µ₃- ² : ² : ². Structural modifications which take place within the ring system on bonding in these various modes are also discussed.     

Chiral biscyclopentadienylniobium(III) complexes

Summary Bimetallic chiral complexes [(⁵-C₅H₄CHMePh)(⁵-C₅H₅) Nb(CO)ML _n ] with ML _n =Co(CO)₄ and HFe(CO)₄ have been prepared and characterized. The lability of the metal-metal bond explains the lack of stereostability of these complexes. The two diastereoisomeric forms of polymetallic chiral complexes [(⁵- C₅H₅CHMePh)(⁵-C₅H₅)Nb(CO)[HFe₃(CO)₁₁] have been synthetized, separated and their stereostability has been investigated. All the complexes were characterized by elemental analysis i.r. and¹H n.m.r. spectroscopy.     

Reaction of the Hexa-1,3,5-triyne Me3SiC≡CC≡CC≡CSiMe3 with Ru4(CO)13(μ 3-PPh): Parallels with the Chemistry of Alkynes and Diynes

Reaction of Ru₄(CO)₁₃(₃-PPh) (1) with the 1,3,5-hexatriyne Me₃SiCCCCC CSiMe₃ under mild thermal conditions affords initially Ru₄(CO)₁₀(-CO)₂{₄-¹,¹,²-P(Ph)C(CCSiMe₃)C(CCSiMe₃) (2), via the facile formation of a P–C bond in a manner similar to that demonstrated previously with alkynes and diynes. The 62-CVE cluster 2 readily decarbonylates to give crystallographically characterised Ru₄(CO)₁₀(-CO)(₄-PPh){₄-¹,¹,²,²-Me₃SiCCC₂CCSiMe₃} (3). Attempts to further incorporate the pendant alkyne moieties in 3 into the Ru₄ coordination environment were partially successful with Ru₄(CO)₁₀(₄-PPh)(₄-¹,¹,³,³-RC₄R') (4, R/R'=SiMe₃/CCSiMe₃) being formed as a minor product together with the unusual toluene coordinated species Ru₄(CO)₇(⁶-C₆H₅Me)(₄-PPh)(₄-¹,¹,³,³-Me₃SiC₄CCSiMe₄) (5). Cluster 3 reacts with an excess of Me₃SiCCCCCCSiMe₃ to give the open chain cluster Ru₄(CO)₉(₃-PPh){₄-²,²,⁴,⁴,-C₄(CCSiMe₃)(SiMe₃)C₄(CCSiMe₃)₃} (6).     

Electrochemical Properties of the Sandwich and Carbonyl π-Complexes of Chromium with Fluoranthene

Redox properties of mono- and binuclear -complexes of Cr with fluoranthene with the composition of (⁶-C₁₆H₁₀)Cr(⁶-C₆H₆), (⁶-C₁₆H₁₀)Cr(CO)₃ and (-⁶,⁶-C₁₆H₁₀)Cr₂(⁶-C₆H₆)(CO)₃ are studied by cyclic voltammetry. Relations between half-wave potentials of redox processes and coordination sites of fragments Cr(⁶-C₆H₆)- and Cr(CO)₃ with the ligand and their nature are found.     

The viscosity of aqueous solutions of alkali and tetraalkylammonium halides at 25°C

The viscosities of most alkali and tetraalkylammonium halides have been measured in water at 25°C. The relative viscosities can be fitted, up to 1M, with the relation _r =1+A c^1/2+B c+D ². TheA term depends on long-range coulombic forces, andB is a function of the size and hydration of the solute. When combined with partial-molal-volume data, the difference B –0.0025V° is mostly a measure of the solute-solvent interactions. IonicB are obtained if the tetraethylammonium ion is assumed to obey Einstein's law. TheD parameter depends on higher terms of the long-range coulombic forces, on higher terms of the hydrodynamic effect, and on structural solute-solute interactions. As such, it cannot be interpreted unambiguously.     

Viscosities of solutions of electrolytes and non-electrolytes in ethylene carbonate at 40°C

The viscosities of dilute solutions of a number of tetraalkylammonium and alkali metal halides, tetraphenylarsonium chloride, sodium tetraphenylborate, tetrabutylammonium tetrabutylborate, water, and 3,3-diethylpentane have been measured in the high-dielectric constant solvent, ethylene carbonate (EC) at 40°C. Crude values of the apparent molar volumes of these solutes have also been obtained. Relative viscosities were fitted to the extended Jones-Dole equation, _r=17#x002B;A c ^1/2+B C+D c ².The pattern of the B coefficients is strikingly similar to that previously observed in the high dielectric constant, linear-chain hydrogen-bonded solvent, N-methylacetamide (NMA). Ionic values for _v and B have been obtained using a variety of splitting techniques. Alkali metal ions have large B coefficients indicating strong cation solvation with the normal order Li>Na>K>Cs. Small anions have positive but much smaller B values than in NMA. The observed order does suggest, however, a small degree of anion solvation. Large organic ions do not display the sharp crossing of the Einstein law,D =2.5_v, uniquely characteristic in H₂O of hydrophobic interaction. The two non-electrolytes have negative B coefficients showing that the Einstein law is not valid at the molecular level and that hydrocarbons are not good models for their isoelectronic tetraalkylammonium ion counterparts. An empirical modification of the Einstein law to account for the finite size of the solvent molecules is discussed. As in NMA the D coefficients are roughly linear in the square of B suggesting that they arise from hydrodynamic origins.     

β-Methallylrhodium(III) supported on a vanadium oxide cluster: Synthesis,structure, and reaction

Reaction of [(³-C₄H₇)₂Rh(CH₃CN)₂]PF₆(³-C₄H₇ = -methallyl) with [n-Bu₄N](VO₃) gives a new ³-allyl cluster [n-Bu₄N]₂[{(³-C₄H₇)₂Rh}₂ (V₄O₁₂)] (I) which is readily converted into a diene cluster, [n-Bu₄N]₂ [{(⁴-C₈H₁₄)Rh}₂(V₄O₁₂)] (II) (C₈H₁₄=2,5-dimethyl-1,5-hexadiene) by reacting with CO or P(OEt)₃;I andII have been characterized crystallographically.     

Mercuration with Mercury(II) Trifluoroacetate of (η6-Aniline)- or (N,N-dimethylaniline)(η5-cyclopentadienyl)iron(II)

The reaction of mercury(II) trifluoroacetate with the hexafluorophosphate of the ⁶-aniline-⁵cyclopentadienyliron(II) cation under reflux in dry ethanol gives rise to N-mono- and N,N-disubstituted mercury-containing salts of this cation. The same mercury-containing salts have been synthesized by the action of mercury(II) trifluoroacetate on the deprotonation product of the (⁶-aniline)(⁵-cyclopentadienyl)iron(II) cation. Direct mercuration of the [⁶-(N,N-dimethylaniline)](⁵-cyclopentadienyl)iron(II) cation into the para position of the benzene ring of the arene ligand has been performed. The reactivity of the compounds obtained has been studied.     

Study of Redox-induced Reactions of Vinylidene and bis-Vinylidene Complexes of Manganese

Oxidative dehydrodimerization of some phenylvinylidene complexes of manganese is studied by cyclic voltammetry. In the case of (⁵-C₅H₅)(CO)₂Mn=C=C(H)Ph, the process occurs as the homolysis of the C–H bond in the radical cation of {(⁵-C₅H₅)(CO)₂Mn=C=C(H)Ph}^+· and the dimerization of intermediate -phenylethinyl cation [(⁵-C₅H₅)(CO)₂Mn–CC–Ph]⁺ to a binuclear dication of bis-carbine type (⁵-C₅H₅)(CO)₂Mn⁺C– C(Ph)=C(Ph)–CMn⁺(CO)₂(⁵-C₅H₅). The reduction of the latter leads to binuclear bis-vinylidene complex (⁵-C₅H₅)(CO)₂Mn=C=C(Ph)–C(Ph)=C=Mn(CO)₂(⁵-C₅H₅). Oxidative dehydrodimerization of complexes (⁵-C₅R₅)(CO)(L)Mn=C=C(H)Ph (R = H, L = PPh₃; R = Me, L = CO) occurs through the immediate C–C coupling of radical cations {(⁵-C₅R₅)(CO)(L)Mn=C=C(H)Ph}^+· and yields binuclear dication bis-carbine complexes (⁵-C₅R₅)(CO)(L)Mn⁺C–C(H)(Ph)–C(H)(Ph)–CMn⁺(CO)(L)(⁵-C₅R₅), whose reduction leads to neutral compounds (⁵-C₅H₅)(CO)₂Mn=C=C(Ph)–C(Ph)=C=Mn(CO)(L)(⁵-C₅H₅). Complex (⁵-C₅H₅)(CO)₂Mn=C=C(Ph)–C(Ph)=C=Mn(CO)₂(⁵-C₅H₅) undergoes the oxidation-induced nucleophilic addition of water, forming cyclic bis-carbene product with a bridge heterocyclic ligand (-3,4-diphenyl-2,5-dihydro-2,5-diylidene)-bis-(⁵-cyclopentadienyldicarbonyl manganese).     

Structure and vibrational spectra of dicyclopentadienylzinc. A DFT study

The quantum-chemical DFT calculations of the Cp₂Zn structure confirm the conclusion made earlier from the vibrational spectra that the sandwich structure (⁵-C₅H₅)₂Zn (A) is not energetically favorable and more favorable are the close in energy -structure (⁵-C₅H₅)(¹-C₅H₅)Zn (B) and -structure (¹-C₅H₅)₂Zn (C). The vibrational spectra of structures B and C with the DFT-derived force fields were calculated. A comparison of the calculated spectra of the isolated Cp₂Zn molecules with the experimental data gives no way of deciding between the B and C structures. It is most likely that the molecule is nonrigid and experiences a strong influence from the nearest environment in solution or in the crystalline state.     

Triple-Decker Complexes. 14. [1] A Model for Refinement of the End-for-End Disordered Cationic Triple-Decker Complex [Cp*Ru(μ-η5:η5-C4Me4P)FeCp*]+

The solid-state structure of the triple-decker salt [Cp*Fe(-⁵:⁵-C₄Me₄P)RuCp*] · CF₃SO₃ shows orientational disorder for the pseudosymmetric cations. A chemically related compound was used to define a restrained structure model. Comparison of different refinement strategies proves that this restrained model is superior to an unrestrained treatment.