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).     

Synthesis and investigation of mono- and binuclear cyano-bridged complexes of rhodium,ruthenium, and palladium

Binuclear Rh^III and Ru^II complexes of the [M¹-CN-M²]⁺BF ₄ ^– (M¹ and/or M² are (⁵-Cp)(³-C₃H₅)Rh and (⁶-C₆H₆)(³-C₃H₅)Ru) type, heteronuclear organometallic compound (⁵-Cp)(³-C₃H₅)RhCNPd(³-C₃H₅)Cl, and mononuclear Rh^III and Ru^II complexes [(³-C₃H₅)LM(MeCN)]⁺ _BF4 ^– (M = Rh, L = ⁵-Cp; M = Ru, L = ⁶-C₆H₆) were synthesized. An electrochemical study of these compounds in solutions demonstrates that the bond between the bridged CN ligand and the metal atoms is rather strong, and there is no dissociation into mononuclear fragments in solutions. The kinetics of the reaction of [(⁵-Cp)(³-C₃H₅)Rh(MeCN)]⁺ _BF4 ^– with halide ions was studied by electrochemical methods. The ligand exchange proceeds by a bimolecular dissociative-exchange mechanism.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 968–973, May, 1995.     

Electrochemical study of allylbenzene and allylcyclohexadienyl complexes of ruthenium

Cyclic voltammetry has been used to study the electrochemical behavior of RuCl(³-C₃H₅)(⁶-C₆H₆) (1), [Ru(PPh₃) · (³-C₃H₅)(⁶-C₆H₆)]BF₄ (2), and Ru(PPh₃)· (³-C₃H₅)(⁵-C₆H₇) (3); the latter was prepared by reacting2 with LiAlH₄. The reduction of1 and2 gives the 19-electron complexes1 ^–. and 2^·, whereas oxidation of3 gives the 17-electron complex3 ^+·. The reactivities of1 ^–·,2 ^·, and3 ^+· are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1126–1128, June, 1993.     

Oxidation of isomeric η6- and η5-fluorenylchromiumtricarbonyl anions

The oxidation of the carbon-centered [(⁶-C₁₃H₉)Cr(CO)₃]^– anion (1 ^–) results in formation of (-⁶:⁶-9,9-bifluorenyl)bis-chromiumtricarbonyl (3) due to coupling of the intermediate carbon-centered radical (1^.). The oxidation of the metal-centered anion [(⁵-C₁₃H₉)Cr(CO)₃]^– (2 ^–), which is isomeric to the 1^– anion, gives an equilibrium mixture of the chromium-centered radical {(⁵-C₁₃H₉)Cr(CO)₃}^. (2 ^.) and its dimer [(⁵-C₁₃H₉)Cr(CO)₃]₂ (6). Radical2 ^. readily reacts with MeI and the solvent (THF); the resulting derivatives, (⁵-C₁₃H₉)Cr(CO)₃R (R=Me (10); R=H (7)), undergo fast ricochet inter-ring ⁵⁶ rearrangements into (⁶-9R-C₁₃H₉)Cr(CO)₃ (R=CH₃ (9); R=H (4)).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1354–1358, July, 1995.The authors are grateful to D. V. Zagorevskii who recorded the mass spectra. This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-05209) and the International Science Foundation (Grant Nos. MQ 4000 and REV 000).     

Electronic effect of the 1-[η5-cyclgpentadienyl-η5-(3)-1,2-dicarbollyliron(II)] group

Conclusions The Taft method was used to determine the electronic effect of the 1-[⁵-cyclopenta-dienyl-⁵-(3)-1,2-dicarbollyliron(II) ] group which displays strong electron-donor properties: _I=–0.22 and _R=–0.20.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1449–1451, June, 1985.     

Examination of the flow behaviour of HEC and hmHEC solutions using structure–property relationships and rheo-optical methods

The effect of solely intermolecular interactions due to hydrophobic alkyl substituents on the flow behaviour of hmHEC solutions was determined via comparison of the structure–property relationships of hmHECs and HECs based on the overlap parameter c[]. For this purpose the ₀–[]–c relationship for HEC was determined to be ₀=8.91·10^–4+8.91·10^–4·c[]+1.07·10^–3(c[])²+1.83·10^–7(c[])^5.56. In addition the structure–property relationship for the longest relaxation time via the –[]–c relationship ·c^1+1/a=2.65·10^–8(c[])²+4.25·10^–8(c[])³+5.44·10^–12(c[])^5.27 has been determined. Although the hmHECs had a higher zero shear viscosity than HECs of comparable overlap parameters at a range of 1<c[]<13, the flow curves could be described via the same –[]–c relationship in that range, indicating a timescale of the intermolecular interactions below the longest relaxation time.The behaviour of the supramolecular structures in solution with an applied shear field was characterized by rheo-optical analysis of the shear thickening behaviour which occurs with addition of surfactant. Contrary to expectations, a slope >1 of the flow birefringence n as a function of shear rate could be observed in double logarithmic plotting. The degree of orientation of the flow birefringence primarily decreases with increasing shear rate, but increases later on at a characteristic shear rate. These two exceptional phenomena can be explained by a pronounced anisotropy of the polymer coils caused by the dilatant flow.This assumption is backed up by the occurrence of a maximum in the dichroism curves which is caused by a finite stability of the aggregated structures in solution. On a molecular basis, these observations agree with the theoretically predicted (Witten and Cohen) transition from intra- to intermolecular polymer micelles. The detected aggregates correspond with the polymer chains that are aligned in one micelle.Abbreviations a Exponent of the Mark–Houwink relationship - c_[]* Critical concentration (determined by intrinsic viscosity) - c_LS* Critical concentration (determined by light scattering) - HASE Hydrophobically modified alkali-swellable emulsions - HEUR Hydrophobically modified ethoxylated urethanes - hmHEC Hydrophobically modified hydroxyethylcellulose - HEC Hydroxyethylcellulose - HPMC Hydroxypropylmethylcellulose - M Molecular mass - MS Molar degree of substitution - n Slope of the flow curve - SEC Size exclusion chromatography - R_G Radius of gyration - Viscosity - ₀ Zero-shear viscosity - _sp Specific viscosity - Longest relaxation time - n Birefringence - n_i Intrinsic birefringence - n_f Form birefringence - n Dichroism - Orientation of the birefringence - ̇ Shear rate     

Role of metal center in reactions of polynuclear nickel(ii) and cobalt(ii) trimethylacetates with 8-amino-2,4-dimethylquinoline

The reactions of 8-amino-2,4-dimethylquinoline (L) (1) with polynuclear nickel(ii) and cobalt(ii) hydroxotrimethylacetato complexes under anaerobic conditions were studied. The nonanuclear cluster Ni₉(₄-OH)₃(₃-OH)₃(_n-OOCCMe₃)₁₂(HOOCCMe₃)₄ gave the mononuclear complex Ni(²-L)(²-OOCCMe₃)₂ (2). The tetranuclear complex Ni₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆ produced the mononuclear complex Ni(²-L)(²-OOCCMe₃)(OOCCMe₃)L (3). At room temperature, the cobalt-containing polynuclear trimethylacetates, viz., the polymer [Co(OH) _n (OOCCMe₃)_2–n ] _x and the tetranuclear complex Co₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆, were transformed into the trinuclear cobalt(ii) complex Co₃(₃-OH)(-OOCCMe₃)₄(²-L)₂(OOCCMe₃) (4). Meanwhile, at 80 °C these compounds generated the binuclear cobalt(iii) complex Co₂(₂²-(HN)C₉NMe₂)₂(-OOCCMe₃)(L)(OOCCMe₃)₃ (5). The structures of the resulting compounds were established by X-ray diffraction analysis. Compounds 2—4 exhibit the antiferromagnetic spin-spin exchange coupling, whereas compound 5 is diamagnetic.     

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.     

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).     

Formation of cobalt(iii) cations with semiquinonediimine ligands

The reactions of polynuclear cobalt(ii) trimethylacetates [Co(OH) _n (OOCCMe₃)_2–n ] _x , Co₆(₃-OH)₂(OOCCMe₃)₁₀(HOOCCMe₃)₄, or Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with an excess of N-phenyl-o-phenylenediamine (1) in toluene followed by treatment with atmospheric oxygen afforded the diamagnetic complex [Co{²-(NPh)(NH)C₆H₄}₂{¹-(NH₂)C₆H₄(NPhH)}]⁺(Me₃CCOO...H...OOCCMe₃)^– (3), whose cation contains the Co^III atom. The reaction of Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with a deficient amount of diamine 1 in acetonitrile under an argon atmosphere gave rise to the antiferromagnetic ionic complex [Co{²-(NPh)(NH)C₆H₄}₂MeCN]⁺[Co₂(₂,²-OOCCMe₃)(₂-OOCCMe₃)₂(²-OOCCMe₃)₂]^–·2MeCN (4), whose cation is an isoelectronic analog of the cation in complex 3. The structures of the new compounds were established by X-ray diffraction analysis.     

Redox-induced η5 ⇔ η3 haptotropy of the fluorenyl ligand in 9-substituted η5-fluorenylmanganesetricarbonyl complexes

It has been shown by cyclic voltammetry in THF within the –90 to 40 °C temperature range that fluorenyl (⁵-9-R-C₁₃H₈)Mn(CO)₃ complexes (R=Bu^t (3) and Ph (4)) undergo two-electron reduction to form allyl type [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– dianions as final products. At low temperatures complexes3 and4 are reduced in two one-electron steps according to the EEC-scheme. The first step is reversible and corresponds to the formation of 19-radical anions 3^–. and 4^–.. TheE ⁰ values for redox pairs3 ^0/–. and4 ^0/–. are –1.88 and –1.73 V, respectively. The further reduction of radical anions3 ^–. and4 ^–. at more negative potentials is accompanied by fast ^{5 3} haptocoordination of the fluorenyl ligand to form 18-dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2–. These dianions obtained by the reduction of complexes3 and4 by the radical anion of pyrene are stable at –80 °C and are characterized by their IR spectra. At room temperature the ^{5 3} hapticity change is a fast and reversible process occurring at the step of 19-radical anions3 ^–. and4 ^–. and leading to the electron deficient 17-species [(³-9-R-C₁₃H₈)Mn(CO)₃]^–., which are reduced easier than the initial complexes. As a result, complexes3 and4 are reduced to the corresponding dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– at room temperature in one reversible two-electron step according to the ECE-scheme. Reactivities of 19e^–-species of the isomeric ⁵- and ⁶-fluorenylmanganesetricarbonyl complexes are compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1347–1353, July, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-05209) and the International Science Foundation (Grant No. REV 000).     

Reactivity of 17- and 19-electron organometallic complexes. Formation of bent sandwich 19-electron radical cation complexes of ruthenium and osmium

The redox behavior of sandwich indenyl complexes of the general formula (⁵-C₉H₇)ML (M=Ru and L=⁵-C₉H₇ (1), ⁵-C₅H₅ (2), ⁵-C₅Me₅ (3); M=Os, L=⁵-C₉H₇ (4)) has been studied in THF, MeCN, and CH₂Cl₂ by cyclic voltammetry and controlled potential electrolysis on a Pt electrode in the –85 to +20 °C temperature range. The title complexes have been found to undergo reversible one-electron oxidation to the corresponding radical cations, whose stabilities and reactivities depend on the nature of both the metal and °-ligands and of the nucleophilic properties of the solvent. The fast interaction of the electrogenerated 17-electron radical cations with nucleophiles yields bent sandwich 19-electron radical cations, [(⁵-C₉H₇)M(L)(Nu)]⁺ (Nu = Cl^–, MeCN, or THF), the latter undergoing one-electron oxidation to the corresponding [(⁵-C₉H₇)M(L)(Nu)]²⁺ dications. In the case of Nu=THF, the reaction of the electrogenerated 17-electron radical cations with nucleophiles appears to be reversible. Radical cations [(⁵-C₉H₇)₂M]^+· (M=Ru, Os) have been characterized by ESR spectra.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2394–2399, December, 1995.     

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.     

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.     

Characterization of water-soluble,cationic polyelectrolytes as exemplified by poly(acrylamide-co-trimethylammoniumethylethacryate chloride) and the establishment of structure-property relationships

The cationic copolymerization products of poly (acrylamide-co-trimethylammoniumethylmethacrylate chloride (PTMAC) having cationic monomer percentages of 8%, 25%, and 50% as well as the cationic homopolymer, were characterized with respect to their molecular dimensions. The light-scattering and viscometric measurements were carried out for molecular weights ranging from 200 000 to 12 800 000 g/mol in 1 M NaCl solution at 25°C. It was possible to establish a relationship between the molecular weight and the two parameters: intrinsic viscosity and radius of gyration, for all four polymers.Rheological investigations of the flow properties in 1 M NaCl solution were also carried out using the polymer with a cationic monomer of 50% (PTMAC 50). Structure-property relationships were formulated which made it possible to describe and predict the shear viscosity, both in the zero-shear region (Newtonian region) and in the shear-dependent region (non-Newtonian region) as a function of the polymer concentration, the molecular weight, and shear rate.Abbreviations a exponent of the []-M relationship - A ₂ 2^nd virial coefficient/mol·cm³·g^–2 - AAm acrylamide - b slope of the flow-curve in the shear-rate dependent region - c concentration/g·cm^–3 - dn/dc refractive index increment/cm³·g^–1 - f function - K constant of the []-M relationship/cm³·g^t-1 - m _c proportion of cationic monomers/mol % - M molecular weight/g·mol^–1 - M _w weight-average molecular weight/g·mol^–1 - M _n number-average molecular weight/g·mol^–1 - NaCL sodium chloride - PAAm polyacrylamide - PS polystyrene - PTMAC poly(acrylamide-co-trimethylammoniumethylme thacrylate chloride) - R_G ^20.5 radius of gyration/nm - TMAC trimethylammoniumethylmethacrylate chloride - shear rate/s^–1 - critical shear rate/s^–1 - viscosity/Pa·s - 0 zero-shear viscosity/Pa·s - _s solvent viscosity/Pa·s - _sp specific viscosity - [] intrinsic viscosity/cm³·g^–1 - relaxation time/s     

Preparation and characterization of a series of poly(acrylamide-co-acrylates), with a copolymer composition between 0–96.3 mol-% acrylate units with the same degree and distribution of polymerization

A series of linear poly(acrylamide-co-acrylates) (PAAm/AAcNa) has been prepared covering a copolymer composition between 0 and 96.3 mol% acrylate units, which have the same degrees of polymerization and chain length distributions. Measurements of viscosity and light scattering have proven that maximum coil dimensions of PAAm/ AAcNa in salt solutions are achieved at about 67 mole-% AAcNa. This so-called maximum behaviour was researched by measuring the radius of gyration, second virial coefficient, molecular weight, preferential solvation, viscosity and absorption bands of the copolymer series. Thus, an increase in the possible ways of arranging AAcNa-AAm-AAcNa units (via H-bonds) will lead to extended coil dimensions and therefore influence the viscosity. In addition, it can therefore be concluded from all these results that the maximum behaviour is real and not influenced by the different distributions of the samples. The copolymer composition can be easily determined by infra-red spectroscopy by use of a proposed relation.Abbreviations A₂ second virial coefficient (mole · cm³ · g^–2) - AAm acrylamide - AAcH acrylic acid - AAcNa sodium acrylate - c polymer concentration (g · cm^–3) - salt concentration (g · cm^–3), (Val · cm^–3) - C _LS critical concentration obtained by light scattering (g · cm^–3) - d _[] viscosity equivalent diameter of a sphere (nm) - E extinction - FW _s formula weights of salt - g _s gram of salt - g _p gram of polymer - GuaCl guanidinium chloride - h ^21/2 root mean square end-to-end distance (nm) - K optical constant for unpolarized incident light (mole · cm² · g^–2) - M molarity (mole · 1^–1) - M _w weight average molecular weight (g · mole^–1) - N _L Avogadro constant 6.023 · 10²³ mole^–1 - P _n number average degree of polymerization - P _w weight average degree of polymerization - PAAm poly(acrylamide) - PAAcH poly(acrylic acid) - PAAcNa poly(sodium acrylate) - PAAm/AAcNa poly(acrylamide-co-sodium acrylate) - R _[] Rayleigh ratio of the scattering at angle (cm^–1) - R _G ² _Z ^1/2 root mean square average radius of gyration (nm) - R _[] viscosity equivalent radius of a sphere (nm) - T temperature (°C), (K) - u excluded volume (cm³ · g^–1) - V molar volume (cm³ · mole^–1) - V _s partial specific volume - X mole fraction - (NH₂) oscillation of deformation - extinction coefficient - ₀ zero shear viscosity (Pa · s), (mPa · s) - _red reduced viscosity (cm³ · g^–1) - [] intrinsic viscosity (cm³ · g^–1) - _a constant of preferential solvation (g · g^–1) - ₀ wavelength of light in vacuo (nm) - chemical potential - v _as stretching vibration - scattering angle (°)     

The reactivity of complexed carbocycles,part 9. New cyclononatetraene cobalt complexes(1)

Summary Two new C₅H₅CoC₉H₁₀ cobalt complexes were shown to contain the cyclononatetraene ligand coordinated in a (3–6-)- and in a (1–25-6-) fashion. The former complex (2) rearranges at elevated temperatures to the latter (3) in a novel type of isomerisation. Complex (3) can be protonated with strong acids and hydrogenated at the uncomplexed double bonds. All compounds were characterised by¹³C n.m.r. spectroscopy.     

On the possibility of existence of η5-π-complexes of C60 fullerene: π-complexes with silicon

Qualitative estimates of possibility of the formation of fullerene ⁵--complexes have been carried out by the MNDO/PM3 method. It was shown, as exemplified by the C₆₀ cluster, that the introduction of five univalent functional groups R (R = H, Cl, Br) to -positions of a separate pentagon of C₆₀ with the formation of [R₅C₆₀]^– anions results in a pronounced increase in the -electron density on the atoms of this five-membered cycle and more favorable conditions for the formation of -bonds with the ⁵-ligand. The nature of the interaction between the atoms of the separate cycle in [R₅C₆₀]^– anion and ⁵-ligand was analyzed by the example of hypothetical sandwich systems R₅C₆₀SiCp. Half-sandwich complexes R₅C₆₀SiX (X = H, Cl) were also investigated. The local energy minima were found on the potential energy surfaces (PES) of systems R₅C₆₀SiCp and R₅C₆₀SiX with C_5p symmetry. These systems transform barrirlessly into q5-7E-complexes with the angular structure if the symmetry restrictions are removed. The most favorable conditions for ⁵--complexes of R₅C₆₀ to form are realized for R = H. The results obtained were compared to those of semiempirical and nonempirical calculations of bis (cyclopentadienyl) silicon.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2422–2429, October, 1996.     

Prediction of the non-Newtonian viscosity and shear stability of polymer solutions

The structure-property relationships derived here permit the prediction of both the zero-shear viscosity ₀, as well as the shear rate dependent viscosity . Using this molecular modeling it is now possible to predict over the whole concentration range, independently of the molecular weight, polymer concentration and imposed shear rate. However, the widely accepted concept: dilute — concentrated, is insufficient. Moreover it is necessary to take five distinct states of solution into account if the viscous behavior of polymeric liquids is to be described satisfactorily. For non-homogeneous, semi-dilute (moderately concentrated) solutions the slope in the linear region of the flow curve (= must be standardized against the overlap parameterc · []. As with the ₀-M-c-relationship, a-M -c- relationship can now be formulated for the complete range of concentration and molecular weight. Furthermore, it is possible to predict the onset of shear induced degradation of polymeric liquids subjected to a laminar velocity field on the basis of molecular modeling. These theoretically obtained results lead to the previously made ad hoc conclusion (Kulicke, Porter [32]) that, experimentally, it is not possible to detect the second Newtonian region.Roman and Italian symbols a exponent of the Mark-Houwink relationship - b exponent of the third term of the ₀-M -c relationship - c concentration /g · cm^–3 - E number of entanglements per molecule - F(r) connector tension - f function - G _i ^A shear modulus; A indicates that it /Pa has been evaluated by a transient shear flow experiment; i is the shear rate to whichG ^A refers to - G storage modulus /Pa - G _p plateau modulus /Pa - H() relaxation spectrum /Pa - h shift factor (₀/_r) - K _H Huggins constant - K _b third constant of the ₀-M -c relationship - K constant of the Mark-Houwink relationship - M molecular weight /g · mol^–1 - M _e molecular weight between two /g · mol^–1 entanglement couplings - N number of segments per molecule - n slope in the power-law region of the flow curve - p p-th mode of the relaxation time spectrum - R gas constant /8.314 J·K^–1·mol^–1 - r direction vector - T temperature /K Greek symbols ß reduced shear rate - shear rate /s^–1 - shear viscosity /Pa·s - _s solvent viscosity /Pa·s - _sp specific viscosity - ₀ zero-shear viscosity /Pa·s - apparent viscosity at shear rate - reduced viscosity - viscosity of polymeric liquid in /Pa·s the second Newtonian region - [] intrinsic viscosity/cm³·g^–1 - screening length/m - /g·cm ^–3 density - relaxation time/s - ₀ experimentally derived relaxation time/s - angular frequency of oscillation Indices conc concentrated - corr slope corrected - cr critical - deg degradation - e entanglement - exp experimental - mod moderately concentrated/semi-dilute - n number average - p polymer - R Rouse - rep reptation - s solvent - sp specific - theo theoretical - weight average - relaxation time - o experimental or steady state - * critical - ** transition moderately conc. — conc. - + transition dilute — moderately cone. Paper presented at the 2nd bilateral U.S.-West German Polymer Symposium, Yountville, the 7th–11th September 1987.     

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.