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Reaction of [(p-cymene)M(OTf)[sub 2]][sub x] with tetramethylpyrrole leads to the formation of [(p-cymene)M(NC[sub 4]Me[sub 4])]OTf, 1 when M = Ru, 2 when M = Os. Complex 1 crystallized in space group P2[sub 1]2[sub 1]2[sub 1] with unit cell dimensions a = 8.928(2) A, b = 13.772(4) A, c = 17.272(6) A, V = 2123.7(11) A[sup 3], and Z = 4. The crystal structure establishes that 1 is a sandwich complex with [eta][sup 6]-cymene and [eta][sup 5]-pyrrolyl ligands. Reaction of 1 or 2 with excess methyl triflate results in alkylation of the pyrrole nitrogen to form ([eta][sup 6]-p-cymene)M([eta][sup 5]-MeNC[sub 4]Me[sub 4])(OTf)[sub 2], 3 when M = Ru and 4 when M = Os. Reactions of 1 or 2 with LiAl(O-t-Bu)[sub 3]H result in nucleophilic attack of hydride on the cymene ligand to form ([eta][sup 6]-cymH)M([eta][sup 5]-NC[sub 4]Me[sub 4]), 5 when M = Ru, 6 when M = Os. Complexes 5 and 6 have been identified by one and two dimensional [sup 1]H NMR spectroscopy. Nucleophilic attack on the cymene ligand of 1 and 2 appears to be quite general, and the products of methoxide addition, ([eta][sup 5]-cymOMe)M([eta][sup 5]-NC[sub 4]Me[sub 4]) 7 when M = Ru, 8 when M = Os havemore » also been characterized by [sup 1]H NMR data. In contrast, reactions of the pentamethylpyrrole complexes 3 and 4 with nucleophiles lead to nucleophilic addition to the pentamethylpyrrole ligand. For example, the reaction of 3 with LiAl(O-t-Bu)[sub 3]H resulted in the formation of ([eta][sup 6]-p-cymene)Ru([eta][sup 4]-MeNC[sub 4]Me[sub 4]H)OTf, 10, which was characterized by an X-ray diffraction study. 10 crystallized in space group P2[sub 1]c with a = 8.153(2) [degrees], b = 17.351 (2) [angstrom], c = 16.508(2) [angstrom], beta = 104.396(13)[degrees], V = 2261.9(7) [angstrom][sup 3], and Z = 4. 28 refs., 5 figs., 3 tabs.« less

The analyses used for measuring the damping of a monolithic beam in steady-state flexural vibration are extended to include beams with a sandwich configuration. The equations so developed are also used for predicting the damping in sandwich beams given the damping characteristics of their constituent parts. Sandwich beams constructed from CFRP and GRP skins, and Nomex or aluminum honeycomb cores, are tested. The damping contributions due to the constituent parts, in particular with respect to skin fibre orientation, are considered. Experimental and theoretical damping results are compared.

The ‘Ru(η-C5Me5)+’ fragment generated by protonation of [{Ru(η-C5Me5)(OMe)}2] by CF3SO3H, reacted with cyclohexene sulfide to give [Ru(η-C5Me5)(η6-C6H6)]+1 and H2S. With 1,4-dithiane no C–S bond activation was observed but instead the successive formation of [Ru(η-C5Me5)(S2C4H8)(CF3SO3)]2 and [Ru(S2C4H8)3]2+3, whereas with 1,3-dithiane two compounds resulting from the sequential activation of C–S bonds were isolated as CF3SO3– salts, namely [{Ru(η-C5Me5)(SMe)(SCH2CHCH2)}2]2+4 and [{Ru[C5Me4CH2S(CH2)3SMe]}2]2+5. The fragment also reacted with neat dichloromethane to give two trinuclear clusters: [{Ru(η-C5Me5)}3(µ-Cl)3(µ3-CH)]+6 and [{Ru(C5Me5)}3(µ-Cl)2(µ-CO)(µ3-CH)]2+7 in 60 and 30% yield respectively. Its reaction with chlorocyclohexane, 1,2-dichlorocyclohexane and 1,2,3,4,5,6-hexachlorocyclohexane (lindane) yielded 1 and various amounts of H2 and HCl. In the case of lindane the conversion was only 30% and yielded a 9:1 mixture of 1 and [Ru(η-C5Me5)(η6-C6H5Cl)]+9. Finally the reaction of C–Cl versus C–O bond activation was compared using 2-chlorocyclohexanone, 2-chlorocyclohexanol and 2,2,6,6-tetrachlorocyclohexanol. It was found that in all cases the C–Cl activation was easier. The first reaction yielded 1, the second the new trinuclear cluster [{Ru(C5Me5)}3(µ-Cl)2(µ-CO)(µ3-CCl)]2+11 similar to 7. The latter reaction depended upon the reaction conditions, but in tetrahydrofuran at 80 °C, an 80% conversion was observed yielding a 1:7: < 1 mixture of 1, [Ru(η-C5Me5)(η6-C6H5OH)]+10 and [Ru(η-C5Me5)(η6-C6H5Cl)]+9 thus demonstrating a high selectivity for C–Cl activation in the presence of C–O bonds.

The sandwich complex commo-[3,3′-Fe{4-(Me2S)-1,2-C2B9H10}2]1 was synthesised. Its meso and DD/LL isomers are easily separated by fractional recrystallization from acetone and were spectroscopically characterized. The charge-transfer salt [3,3′-Fe{4-(Me2S)-1,2-C2B9H10}2]+[ddq]˙–2 was formed between the DD/LL-1 racemate and 2,3-dichloro-5,6-dicyano-p-benzoquinone (ddq). X-Ray crystallography revealed an increase in the iron-dicarbollide distance on oxidation of DD/LL-1(Fe–C2B3 1.50 A) to the cation in 2(Fe–C2B3 1.54 A). The latter is the first example of a cationic bis(dicarbollyl)metal complex to be crystallographically characterized. The cations and anions pack to form alternating layers in the crystal of 2. Within the [ddq]˙– layer the anions form zigzag chains linked via intermolecular N ⋯ Cl electrostatic interactions (N ⋯ Cl 3.21 A). The cation and anion layers are crossed-linked by weak CH ⋯ O hydrogen bonds between the oxygen atoms of the [ddq]˙– anions and some of the cage CH hydrogen atoms of the cations. Between 5 and 270 K the corrected molar susceptibility of 2 follows the Curie–Weiss law, with a θ value of –2.5 K. The single-crystal electrical conductivity of 2 at room temperature is less than 10 –8 S cm–1.

Reaction of bis(cyclopentadienyl)-2,3-dimethylzirconaindole, obtained by addition of 2-butyne to benzynezirconocene, with PCl 3 , affords 1-chloro-2,3-dimethylphosphindole (1-chloro 2,3-dimethylbenzophosphole in a one-pot reaction and in moderate yield. Treatment of this compound with potassium and subsequent reaction with [SmI 2 (THF) 2 ] afforded bis(η 5 -2,3-dimethylphosphindolyl) bis(tetrahydrofuran)samarium. Treatment of the PP bonded bis(dibenzophospholyl with Sm metal activated by HgCl 2 also affords a complex of Sm II that was shown to be bis(η 1 -dibenzophospholyl tetrakis(tetrahydrofuran)samarium, a σ-Sm phosphide complex. Both complexes were analysed by X-ray crystallography.

L'irradiation avec de la lumiere visible de complexes sandwich du Ce(IV) (tetraphenyl-et-octaethylporphyrines) en presence d'un electron donneur comme la triethylamine conduit a leur photoreduction. Ce processus est analyse en utilisant les spectroscopies d'absorption et de resonance paramagnetique electronique (RFE). L'irridiation photochimique du Ce(IV) [TPP(-2)] 2 aboutit a la formation de [Ce(III) TPP(-2)TPP(-2)] - . L'oxydation de ce compose en presence de chloroforme comme accepteur d'electron est aussi observee. La photoreduction de Ce(IV)[OEP(-2) OEP(-2)] est plus compliquee et il y a formation d'un compose neutre [Ce(III) OEP(-1) OEP(-2)]qui presente un spectre RPE typique des lanthanoides(III) de bisporphyrines

Novel bis(phthalocyaninato)lutetium(III) complexes substituted with long n-alkyl chains have been synthesized. These complexes, 1a–c, show three kinds of discotic mesophase (Dhd, Dob.d, and DL). Also 1a–c display the three primary colours (red, green, blue) of electrochromism in their solutions. The solutions of oxidized species of 1a–c are nearly red, although those of conventional bis(phthalocyaninato)lutetium(III) complexes are orange.

POM-in-POM: A Wells–Dawson polyoxometalate sandwich compound with a double cubane core consisting of six vanadium atoms has been synthesized (see structure). Cluster formation was followed by mass spectrometry and the reduction of the double cubane was studied by a novel technique combining mass spectrometry and spectroelectrochemistry.

Metallation of a variety of α,ω-dienes has been explored with an η(9),η(5)-bis(indenyl)zirconium sandwich compound and an ansa-titanocene dinitrogen complex. The η(9),η(5)-bis(indenyl)zirconium sandwich compound, (η(9)-C(9)H(5)-1,3-Pr(2))(η(5)-C(9)H(5)-1,3-(i)Pr(2))Zr, served as an isolable source of Negishi's reagent and readily formed a kinetic mixture of cis and trans diastereomers of the corresponding zirconacyclopentanes upon diene metallation. For pure hydrocarbon substrates such as 1,6-heptadiene and 1,7-octadiene, an equimolar amount of cis and trans diastereomers were the kinetic products; isomerization to the thermodynamically favoured trans isomers was observed over time at ambient temperature or upon heating to 105 °C, respectively. By contrast, substitution of the methylene or ethylene spacer in the α, ω-diene with a fluorenyl group (e.g. 9,9-diallylfluorene) resulted in exclusive kinetic formation of the trans diastereomer. Amino-substituted dienes were also readily cyclised and one example was characterised by single-crystal X-ray diffraction. Similar studies were also conducted with the ansa-titanocene dinitrogen complex, [Me(2)Si(η(5)-C(5)Me(4))(η(5)-C(5)H(3)-3-(t)Bu)Ti](2)(μ(2),η(1),η(1)-N(2)), and both kinetic and thermodynamic selectivities evaluated. The use of a C(1) symmetric ansa-metallocene increases the number of isomeric possibilities. For diallyl tert-butyl amine, diene metallation was more selective than for the bis(indenyl)zirconium sandwich compound and isomerization was also more rapid. Preliminary functionalisation reactivity for both the zircona- and titanocycles was also explored.

Ethylene-norbornene (E-N) terpolymerization experiments using the linear olefin 1-octene (O) or the alicyclic vinylcyclohexane (VCH) were conducted with two different ansa-metallocene compounds Zr(?5 :?5 -C5H4CPh2C13H8)Cl2] (1) and [Zr{(?5 -2,5-Me2C5H2)2CHMe}Cl2] (2). The terpolymers obtained were investigated in detail by determining microstructure and termonomer contents by 13C NMR, molar masses, and thermal properties. Chain end group analysis gave insight into factors that influence termonomer insertion and chain termination. Terpolymer molar masses were lower than those of the corresponding copolymers, those from 1 being higher than those from 2. This is related to the lower tendency of catalyst 1 to give ?-H elimination at a last enchained E unit as revealed from the low amount of vinyl chain end groups in 1 H NMR spectra. In VCH terpolymers from catalyst 1, only vinylene end groups, arising from 2,1 VCH insertions after one last inserted E unit, are present. This along with the lower activity reveals that VCH insertion is more difficult with this catalyst than with catalyst 2. Furthermore, all experiments showed that in general VCH is more difficult to coordinate to an active catalyst than O. While catalyst 1 provides higher molar masses, catalyst 2 enables to reach higher activities, higher N and termonomer contents, and higher Tg values. Finally, it was found that termonomer content greater than 3 mol % clearly affects Tg values. Thus, preparation of norborneneethylene-R-olefin terpolymers with high Tg and attractive molar masses was achieved in high yield by metallocene catalysts.

Complexes of the di- and triphosphacyclopentadienyl ring systems of the type [Ru(η5-P2C3tBu3)(η5-C8H11), [Ru(η5-P3C2tBu2)(PPh3)PPh2C4H4], [Rh(η5-P2C3tBu3)(η4-diene)], (diene = hexa-1, 5-diene, 1,5-cyclooctadiene), and the novel hydrido complex [RhH(η1-P3C2tBu2)(η5-C5Me5) (PPh3)], are described, and 1H, 31P, and 13C NMR data reported and discussed. The structures of [Rh(η5-P2C3tBu3)(η4- COD)] and [RhH(η1-P3C2tBu2)(η5-C5Me5)PPh3] have been determined by X-ray diffraction studies.

The complexes [(C8H8)Ln(μ-Cl)(THF)n]2 (Ln = Y, La, Pr, Sm, Gd, Dy, Er, Lu) react with Na(C5Me4H) in THF to yield complexes (C8H8)Ln(C5Me4H)(THF)x (Ln = Y, La, Pr, Sm, Gd, Dy, Er, Lu). Crystals of (C8H8)La(C5Me4H)(THF) 2 (2) are monoclinic, space group P21/n with a = 850.80(15), b = 1183.5(2), c = 2290.1(5) pm, β = 96.707(16)°, V = 2273.8(8) × 10−30 m3 and Z = 4. Least-squares refinement on the basis of 3070 reflections (Fo > 6σ(Fo)) led to a final R of 0.0305. Compound (C8H8)Lu(C5Me4H) (8) crystallizes monoclinic, space group P21/m with a = 927.6 (2), b = 1431.3(4), c = 1114.4(2) pm, β = 90.41(1)°, V = 1479.5(5) × 10−30 m3 and Z = 4. Least-squares refinement on the basis of 2329 reflections (Fo> 4σ(Fo)) led to a final R of 0.0276.

The metal-metal interaction in the mixed-valence ferrocenium salt [ trans -Cp★FeLFeCp★] + PF 6 − ([ 5 + ]PF 6 − ) (Cp★ = C 5 Me 5 , L = [C 5 H 3 SiMe 2 ] 2 ) was investigated by cyclic voltammetry, electron spectroscopy, EPR and temperature dependent Mossbauer spectroscopy. The compound is best described as a valence-localised system (class I according to Robin and Day).

Ethylcycloarsoxan, (C2H5AsO)n, ist ein Ionophor fur Alkalikationen mit anpassungsfahiger Ringgrose. Na{cyclo-(C2H5AsO)4}2SCN (1) und [K{cyclo-(C2H5AsO)5}2]SCN (2) wurden durch die Umsetzung von (C2H5AsO)n und MSCN (M = Na, K) in Acetonitril dargestellt und durch Rontgenstrukturanalyse charakterisiert. Das Natriumatom in 1 ist annahernd quadratisch-antiprismatisch von 8 Sauerstoffatomen umgeben und weist NaO-Abstande zwischen 2,516(5) und 2,662(5) A auf. Fur das Kaliumatom in 2 wird eine nur wenig verzerrte pentagonal-antiprismatische Koordinationsgeometrie mit KO-Abstanden zwischen 2,90(1) und 3,06(1) A beobachtet. Bedingt durch den kleineren Ringdurchmesser der Arsoxanringe sind die Antiprismen in 1 und 2 entlang ihrer Hauptachse deutlich gestreckt im Vergleich zu analogen Kronenetherkomplexen. Ethylcycloarsoxane, (C2H5AsO)n, an Ionophore with Adaptable Ring-Size in the Alkali Metal Complexes [Na{cyclo-(C2H5AsO)4}2]SCN and [K{cyclo-(C2H5AsO)5}2]SCN Ethylcycloarsoxane, (C2H5AsO)n, is an ionophore for alkali metal cations with adaptable ring-size, [Na{cyclo-(C2H5AsO)4}2]SCN (1) and [K{cyclo-(C2H5AsO)5}2]SCN (2) have been prepared by the reaction of (C2H5AsO)n with MSCN (M = Na, K) in acetonitrile and characterised by X-ray structural analysis. The sodium atom in 1 is coordinated in an approximately quadratic-antiprismatic fashion by 8 oxygen atoms and displays NaO distances in the range 2.516(5) and 2.662(5) A. A virtually undistorted pentagonal-antiprismatic coordination geometry with KO distances between 2.90(1) and 3.06(1) A is observed for the potassium atom in 2. As a result of the smaller diameter of the arsoxane rings the antiprisms in 1 and 2 are significantly stretched along their main axis in comparison to analogous crown ether complexes.

Braunrote Di(phthalocyaninato(1−))-praseodym(III)-polyhalogenide [Pr(Pc−)2]Xy (X = Br, I) variabler Zusammensetzung (1 ≤ y ≤ 2,5) bilden sich bei der (elektro)chemischen Oxydation von [Pr(Pc2−)2]−. Die thermische Zersetzung der Polyhalogenide bei 250°C liefert partiell oxydiertes, grunes α-[PrPc−Pc2−]. Wegen der starken Spin-Spin-Kopplung der Phthalocyanin-π-Radikale reduziert sich das magnetische Moment fur alle Komplexe auf den Beitrag des PrIII-Kations von ca. 3,0 B.M. Grun metallisch glanzende Nadeln von [Pr(Pc−)2]Br1,5 kristallisieren in der tetragonalen α-Modifikation: Raumgruppe P4/nnc mit a = 19,634(5) A, c = 6,485(2) A; Z = 2. In dem Sandwich-Komplex ist PrIII von den Isoindol-N-Atomen der beiden fast planaren, um 41° gegeneinander gedrehten Pc−-Liganden achtfach-koordiniert. Die stapelformige Anordnung der Pc−-Liganden bedingen den quasi-eindimensionalen Charakter der Struktur langs [001]. Die Uberperiode langs [001] ist eine Folge der Verteilung der Pr-Atome auf zwei unvollstandig besetzte kristallographische Positionen im Abstand von c/2 und der in gleicher Richtung verlaufenden ungeordneten Ketten der Bromatome. Die Pulverdiffraktogramme von [Pr(Pc−)2]Br2, [Pr(Pc−)2]I2 und [PrPc−Pc2−] bestatigen die tetragonale α-Modifikation auch fur diese Komplexe. Der Tribromid-Gehalt korreliert mit der Besetzung der Pr(2)-Lage. Im UV-VIS-NIR-Absorptionsspektrum eines Dunnfilms von [Pr(Pc−)2]Bry wird die intensive Bande bei 13,9 kK dem B-, die bei 19,5 kK dem Q-Ubergang zugeordnet. Die fur isolierte dimere Pc−-π-Radikale charakteristische D-Bande liegt bei 9,1 kK. Sie verschiebt sich mit zunehmender Elektronendelokalisierung aufgrund wachsender Stapel bathochrom, wobei sie sukzessive bei 6,05, dann 3,3 kK auftritt. Die MIR- und Resonanz-Raman(RR)-Spektren von α-[Pr(Pc−)2]Xy, (X = Br, I) zeigen die fur Pc−-π-Radikale bekannten diagnostischen Banden. Im RR-Spektrum des Polyiodids dominiert die Obertonprogression der totalsymmetrischen (I—I)-Valenzschwingung des Triiodids (108 cm−1). Die FT-Raman-Spektren sind ebenfalls von der totalsymmetrischen Valenzschwingung des Polyhalogenids gepragt (Br3−: 145 cm−1; I3−: 105 cm−1; I5−: 151 cm−1). Preparation and Properties of Tetragonal α-Di(phthalocyaninato(1−))praseodymium(III)-polyhalides; Crystal Structure of α-[Pr(Pc−)2]Br1.5 Brown red di(phthalocyaninato(1−))-praseodym(III)-polyhalides [Pr(Pc−)2]Xy (X = Br, I) of variable composition (1 ≤ y ≤ 2.5) are formed by (electro)chemical oxidation of [Pr(Pc2−)2]−. The thermical decomposition of these polyhalides at 250°C yields partially oxidized, green α-[PrPc−Pc2−]. Due to strong spin–spin coupling of the phthalocyanin-π-radicals only PrIII contributes to the magnetic moment of ca. 3.0 B.M. for all complexes. Green metallic prisms of [Pr(Pc−)2]Br1.5 crystallize in the tetragonal α-modification: space group P4/nnc with a = 19.634(5) A, c = 6.485(2) A; Z = 2. In the sandwich complex PrIII is eightfold coordinated by the isoindoline N-atoms of the two staggered (41°), nearly planar Pc−- ligands. The quasi-onedimensional character of the structure along [001] is due to the infinite columns of Pc− ligands. The superperiod along [001] is a consequence of the distribution of the Pr atoms onto two incompletely filled crystallographic positions at a distance of c/2 and the disordered chains of the bromine atoms extending in the same direction. Powder diffractograms of Pr(Pc )2Br2, [Pr(Pc−)2]I2 und [PrPc Pc2−] confirm the tetragonal α-modification of these complexes, too. The content of tribromide correlates with the population of the Pr(2)-site. In the UV-VIS-NTR absorption spectrum of a thin film of Pr(Pc )2Br, the intense bands at 13.9 and 19.5 kK are assigned to the B and Q transition, respectively. The D band at 9. kK is characteristic for isolated dimeric Pc−-π-radicals. Due to increasing electron delocalisation as a result of the growing columns the D band is shifted to lower energy appearing successively at 6.05 and 3.3 kK. The mir and resonance Raman (RR) spectra of α-[Pr(Pr−)2]Xy, (X = Br, I) show the well known diagnostic bands for Pc−-π-radicals. Thc RR spectrum of the polyiodide is dominated by the overtone progression of the totally symmetric (I-I) stretching vibration of the triiodide at 108cm−1. The FT-Raman spectra are also marked by the totally symmetric stretching vibration of the polyhalides (Br3 : 145cm 1; 13−:105cm−1; I5− 151 cm−1).

Cp*(η4-1,3-diene)Cr compounds have been prepared either by reacting Cp*(η3-C3H5)2Cr with a diene or by reducing Cp*Cr(THF)Cl2 with activated-Mg in the presence of the diene. These coordinatively and electronically unsaturated species readily form adducts with CO or P-donor ligands. The reaction of Cp*(η4-1,3-C4H6)Cr with further butadiene leads to the formation of Cp*(η3,η3-octadienediyl)Cr which in turn reacts with a disubstituted alkyne (RC2R) with addition to the 2,7-positions of the octadienediyl chain to give Cp*(η1,η2,η1-R2C10H12)Cr species. The crystal structures of representative compounds have been established by X-ray diffraction.

The title compounds have been prepared by reacting a Cp′CrCl2 or a (η3-allyl)2CrCl species with either an allylmagnesium halide or a substituted cyclopentadienyllithium derivative. The compounds react further at room temperature to give the dinuclear species [Cp′(μ-η3-allyl)Cr]2, and with P-donor ligands with reductive coupling of the allyl groups to give Cp′(η2,η2-1,5-hexadiene)CrPR3 species. Diene exchange is observed upon reacting the hexadiene compounds with butadiene or cyclohexadiene. The crystal structures of [Cp(μ-η3-C3H5)Cr]2, [(η5-indenyl)(μ-η3-C3H5)Cr]5)Cr2, (η5-indenyl) (η2,η2-1,5-hexadiene)CrP(OMe)3 and three compounds containing a 1,3-diene, viz. Cp(η4-1,3-C4H6)CrPMe3, (η5-Me5C5)(η4-1,3-C4H6)CrCO and Cp(η4-1,3-cyclohexadiene)CrP(OMe)3 have been established by X-ray diffraction.

Reaction of ethyl lithiodiazoacetate with the cationic [Fe(arene)Cp] complexes 1 and 2 produces σ-adducts 6 and 7. Upon treatment with a catalytic amount of Rh₂(OAc)₄ in CH₂Cl₂, the adducts are transformed to metallocarbenes, which react further by 1,2- hydrogen migration. While reaction of 6 results in a mixture of equilibrating E and Z stereoisomers 8 and 9, a single product (10) is obtained from 7.

Cleavage of the chloro-bridged Ru II dimer, [( p -isopropyltoluene)Ru(Cl) 2 ] 2 with AgBF 4 in acetone and refluxing the product in trifluoroacetic acid with an excess of p -isopropyltoluene leads to the formation of the dicationic bis(arene) Ru II complex, [( p -isopropyltoluene) 2 Ru][BF 4 ] 2 , in nearly quantitative yield. Strong upfield shifts are observed in the 13 C NMR spectrum of the arene carbon atoms of p -isopropyltoluene following coordination and an investigation of the electrochemistry of this complex shows that it undergoes an irreversible reduction in nitromethane solvent at −0.78 V versus an Ag/AgCl reference electrode. An X-ray crystal structure determination of the complex shows that the complex consists of a Ru II center located between two p -isopropyltoluene ligands that are coordinated in an η 6 manner. The arene rings are separated by a distance of 3.450 A and are essentially coplanar with a dihedral angle of 178.4°. The crystals are monoclinic, space group P 2 1 / n wth lattice constants a = 10.094(2) A, b = 12.996(3) A, c = 17.371(3) A, β = 94.90(1)° and V = 2270.4(8) A 3 . Convergence to conventional R values of R = 0.0711 and R w = 0.0854 with a goodness-of-fit of 1.15 was obtained for 280 variable parameters and 2976 reflections with I > 0σ( I ).

(η5-Cyclopentadienyl)(η5-ligand)ruthenium(II) (ligand = 1,2,3,4,5-η6-exo-methoxy-d3-7-oxo-2,4-cycloheptadienyl-2d 3a, 1,2,3,4,5-η6-exo-methoxy-7-oxo-2,4-cycloheptadienyl-2d, 1,2,3,4,5-η6-exo-methoxy-7-oxo-2,4-cycloheptadienyl, and 1,2,3,4,5-η6-exo-ethoxy-7-oxo-2,4-cycloheptadienyl) was isolated in fairly good yields by treatment of (η5-C5H5)(η6-tropone)ruthenium(II)BF4 with KOH in CD3OD, CH3OD, CH3OH, and ethanol, respectively. The selectively deuterated tropone-2d was readily removed by photolysis of 3a accompanied by demethoxylation with visible light in the presence of large excess of P(OCH3)3.

Subpicosecond time-resolved absorption studies have been carried out on a cerium porphyrin-phthalocyanine sandwich mixed dimer in the liquid and solid states. Following excitation, two relaxation processes having time constants of ≈ 1 and ≈ 40 ps are observed irrespective to the nature of the environment. The first process is attributed to the relaxation of the excited state of the dimer to a low-lying charge transfer state. The second one, much slower, accounts for the relaxation of the charge transfer state back to the ground state. The comparison of the liquid and solid phase data clearly allows the role of the solvent in the relaxation processes to be eliminated.

Bis(mesityl)niobium (1) promotes hydroborations of alkenes by catecholborane but via an indirect mechanism.

(η 6 -Hexaalkylbenzene)(η 4 -naphthalene)iron- and (η 6 -hexaalkylbenzene)(η 4 -1,4-dimethylnaphthalene)iron-complexes (alkyl = methyl and ethyl) can be prepared from bis(ethylene)(toluene)iron, the desired naphthalene derivative and three molecules of butyne or hexyne respectively. The products are formed by stoichiometric [2 + 2 + 2]-cyclic additions of the alkynes and a complete exchange of the coordination sphere of the metal below room temperature. The naphthalene ligands are bonded by four carbon atoms only, which causes an electronic separation inside the bicyclus. One can characterize the coordinated π 4 -moiety, which behaves like an 1,3-cyclohexadiene ligand, whereas the free π 6 -moiety acts like an annelated benzo ring. This causes a folding of the naphthalene along the line Cl-C4 by 34°, away from the iron atom, and significant changes in the NMR spectra. In contrast to other (arene)(alkylnaphthalene)iron-complexes, with toluene or p -xylene as arene ligands, which decompose around 0°C, the hexaalkylarenes stabilize this type of compound significantly [T dec. for (hexamethylbenzene) (naphthalene)iron ca. 140°C]. Electrochemical investigations indicate a reversible redox equilibrium of the neutral complexes with the mono- and dications. However, the oxidized species are only stable at low temperatures. Extended Huckel MO-theoretical calculations indicate a structural change for the second oxidation product, since the energy of the π 6 : π 6 -dictation is lower than that of the η 6 :η 4 -dictation. Reactivity studies qualify (hexametylbenzene)(naphthalene)iron as a selective catalyst for the cyclic trimerization of ester-substituted alkynes at temperatures as low as −30°C, but not for butyne or hexyne, not even at elevated temperatures.

The relative merits of various routes to ring-substituted cycloheptatrienyl complexes [M(CO) 3 (η 7 -C 7 H 6 R)] + (M = Cr, Mo or W) have been explored. Substitution at a metal coordinated C 7 H 7 ring is effected via addition, thermal rearrangement and subsequent H − abstraction. Thus reaction of [Mo(CO) 3 (η 7 -C 7 H 7 )] + with NaOMe gives [Mo(CO) 3 {η 6 -(7- exo -OMe)C 7 H 7 }], which affords substituted cycloheptatriene complexes [Mo(CO) 3 {η 6 -(7- exo -R)C 7 H 7 }] [R = Me ( 1 ); t Bu ( 2 ); C 6 H 4 -F- p ( 3 )] by reaction with RMgX; direct addition of CCPh to [M(CO) 3 (η 7 -C 7 H 7 )] + to give [M(CO) 3 {η 6 -(7- exo -CCPh)C 7 H 7 }] [M = Cr ( 4 ); M = Mo ( 5 )] is brought about by reaction with alkynyl cuprate reagents. Thermolysis of 1–4 gives isomeric mixtures of rearranged cycloheptatriene complexes [M(CO) 3 {η 6 -( n -R)C 7 H 7 }] ( n = 1, 2 or 3), which contain a CH 2 ring carbon with an exo hydrogen accessible to H − abstraction by Ph 3 C + to yield the ring-substituted cycloheptatrienyl complexes [M(CO) 3 (η 7 -C 7 H 6 R)] + [M = Mo; R = Me ( 7 ); t Bu ( 8 ); C 6 H 4 -F- p ( 9 ); M = Cr, R = CCPh ( 10 )]. Alternatively, substituted cycloheptatrienes C 7 H 7 R and cycloheptatrienyl ions C 7 H 6 R + may be coordinated directly to [M(CO) 3 (NCMe) 3 ]. Reaction of 7-Me-C 7 H 7 with [M(CO) 3 (NCMe) 3 ] (M = Cr, Mo or W) in THF affords [M(CO) 3 {η 6 -(7-Me)C 7 H 7 }] as a (metal dependent) exo / endo isomeric mixture at C(7). The reaction of the cycloheptatrienyl ions C 7 H 6 R + (R = Me, t Bu, C 6 H 4 -F- p , OCPh) with [M(CO) 3 (NCR′) 3 ] (M = Mo, R′= Me; M = W, R′=′Pr) proceeds at room temperature in THF or CH 2 Cl 2 and provides convenient syntheses of 7 , 8 , 9 , [Mo(CO) 3 {η 7 -C 7 H 6 (CCPh)}] + ( 11 ) and [W(CO) 3 (η 7 -C 7 H 6 R)] + [R = Me ( 12 ); C 6 H 4 -F- p ( 13 )]. Complexes 7, 8, 9, 12 and 13 are useful starting materials for investigation of the chemistry of ring-substituted cycloheptatrienyl complexes, as exemplified by the syntheses of [MI(CO) 2 (η 7 -C 7 H 6 Me)] [M = Mo ( 14 ); M = W ( 15 )] and the sandwich complex [Mo(η 6 -toluene)(η 7 -C 7 H 6 Me)] + ( 16 ).

Oxidation reactions of bis(phthalocyaninato)titanium(IV), Pc 2 Ti, and bis(phthalocyaninato)tin(IV), Pc 2 Sn, with I 2 and HNO 3 lead to the formation of the species [Pc 2 M](I 3 ) 0.66 and [Pc 2 M]NO 3 , respectively [M=Ti(IV), Sn(IV)]. Exchange of the NO 3 - group with PF 6 - leads to the species [Pc 2 M]PF 6 . Reduction of these oxidized saltlike species with NaBH 4 results in the formation of the respective precursors Pc 2 Ti and Pc 2 Sn. The structure of the complex [Pc 2 Ti] (I 3 ) 0.66 has been elucidated by a low-temperature (-110 o C) single-crystal X-ray study

The enantioselective catalytic epoxidation of unfunctionalized alkyl and aryl olefins was conducted using titanocene and niobocene peroxide complexes incorporating a C 2 -symmetrical binaphthylcyclopentadienyl ligand (BpDMCp). Enantiomeric excesses up to 20% and activities up to 55 turnovers were obtained with the application of our chiral bis(binaphthylcyclopentadienyl)-derived metallocenes. A significant decrease in the enantioselectivity for the epoxidation of trans -3-hexene was observed when the metal was changed from titanium to niobium in these binaphthyl-derived C 2 -symmetrical complexes. The preparation of the bis(binaphthylcyclopentadienyl)-chloroniobium peroxide complexes and bis(indenyl)chloroniobium peroxide is described.

The electronic structure of diazaferrocene is shown to be similar to that of ferrocene and no evidence has been found for a conformational preference in the former. A smaller observed barrier for the ring rotation in the tetra-tert-butyl substituted diazaferrocene compared to that in the substituted ferrocene analog is attributed to more facile distortional modes in the heterocyclic system. Tetra-tert-butyl-diazanickelocene has been synthesized from NiCl2 and Li(C4H2tBu2N) and its crystal structure determined. Small, albeit significant structural differences in the diazaferrocene, -cobaltocene, -nickelocene series are explained in terms of the sequential filling of π-antibonding levels. In the bent Main Group species diazastannocene or -plumbocene an electronic situation different from that for the normal metallocenes gives rise to a conformational preference with both nitrogens pointing along the direction of maximum opening of the aza-Cp ring planes.

Cyclodextrins form with some aromatic ruthenium complexes crystalline inclusion compounds, the reaction being very selective regarding the geometry and the functional groups of the guest molecule. The structure of the 2:1 inclusion compound of benzene(cyclopentadienyl)ruthenium(II)-hexafluorophosphate with α-cyclodextrin was elucidated by an X-ray structure analysis.

The first metallocenium metallacarboranide salts have been synthesized and isolated. The title compounds were prepared by reaction of cobaltocene and CoCl 2 or FeCl 2 with the carborane anion Et 2 C 2 B 4 H 5 - in THF solution, in which the oxidation of two M(II) metal centers to M(III) is accompanied by reduction of two B-H-B bridging protons to H 2 .

A method for the high-yield syntheses (up to 85%) of the two new compounds ([eta][sup 5]-C[sub 5]H[sub 5])Ti(S[sub 2]CCH[sub 3])[sub 3] (1) and ([eta][sup 5]-C[sub 5]H[sub 5])Nb([eta][sup 2]-S[sub 2])(S[sub 2]CCH[sub 3])[sub 2] (2) from ([eta][sup 7]-C[sub 7]H[sub 7])M([eta][sup 5]-C[sub 5]H[sub 5]) (M = Ti, Nb) and dithioacetic acid, CH[sub 3]CS[sub 2]H, is described. Both compounds are characterized by elemental analysis, [sup 1]H and [sup 13]C NMR spectroscopy, infrared spectroscopy, mass spectrometry, and X-ray crystallography. Compound 1 crystallizes in orthorhombic space group Pbca. Compound 1 exists in the crystalline state as discrete seven-coordinate molecules; the coordination environment of the central Ti(IV) atom is a slightly distorted pentagonal bipyramid. A [eta][sup 5]-C[sub 5]H[sub 5] ring occupies one axial site, two bidentate dithioacetate groups occupy four equatorial sites, and a third bidentate dithioacetate group spans the remaining axial and equatorial sites. The average equatorial Ti-S distance of 2.619 [angstrom] is appreciably longer than the axial Ti-S distance, 2.545(3) [angstrom]. Compound 2 crystallizes in space group P2[sub 1]/c. Crystals of 2 consist of discrete seven-coordinate molecules; the coordination environment of the central Nb(V) atom is a severely distorted pentagonal bipyramid. A [eta][sup 5]-C[sub 5]H[sub 5] ring occupies one axial site, and a [open quotes]side-on[close more » quotes] bonded disulfide, [eta][sup 2]-S[sub 2], occupies two equatorial sites. The remaining positions are occupied by two nonequivalent bidentate dithioacetate ligands. A variable-temperature [sup 1]H NMR study on 2 shows rapid interconversion between the two dithioacetate environments at 47[degrees]C ([Delta]G[double dagger] = 1.7 [+-] 0.1 kcal mol[sup [minus]1]). 46 refs., 1 fig., 7 tabs. « less

The lone pair electrons of the two adjacent phosphorus atoms of the C2But2P3 ring in the triphospha0-ferrocene complex [Fe(η5-C5Me5)(η5-C2But2P3)] can ligate to other metal centres to afford novel bi- and tetrametallic complexes, whose structures have been elucidated by NMR and single-crystal X-ray studies. In the reaction of [Fe(η5-C5Me5)(η5-C2But2P3)] with Ni(CO)4 the tetrametallic complex [Fe(η5-C5Me5)(C2But2P3)Ni(CO)2]2 is formed. This complex is of particular interest because it represents the first example of the intermolecular interlinkage of two phospha-ferrocene units by two metal centres. A six-membered ring consisting of four phosphorus and two nickel atoms forms the core of the molecule and exhibits a boat configuration. The starting material [Fe(η5-C5Me5)(η5-C2But2P3)] reacts with Cr(CO)5(thf), W(CO)5(thf) and Fe2(CO)9 to yield the η5-complexes [Fe(η5-C5Me5)(η5-C2But2P3)M(CO)n] (M = Cr, W, n = 5; M = Fe, n = 4). Variable-temperature η31P{1H} NMR studies reveal that these complexes are fluxional in solution.

Two molar equivalents of 1-cyclohexylindenyllithium were treated with ZrCl 4 (thf) 2 to give a ca . 1:1 mixture of meso - and rac -bis(1-cyclohexylindenyl)ZrCl 2 ( meso -/ rac - 4 ). Catalytic hydrogenation yielded a corresponding mixture of the bis(1-cyclohexyl-4,5,6,7-tetrahydroindenyl)ZrCl 2 diastereoisomers meso - 5 and rac - 5 . In both cases the diastereomers were separated by fractional crystallization. Complexes meso - and rac - 5 were characterized by an X-ray crystal structure study. In the crystal the molecular structure of complex rac - 5 is C 2 -symmetric, with the annulated six-membered ring systems arranged towards the open front side of the bent metallocene wedge and the cyclohexyl substituents oriented anti -periplanarly in the lateral sectors. In contrast complex meso - 5 has only one of the cyclohexyltetrahydroindenyl ligands arranged in this way, the cyclohexyl substituent of the other one pointing towards a central front position and the annulated six-membered ring being situated in the lateral position ( C 1 -symmetry).

Bis(hexamethylbenzene)iron dication (HMB) 2 Fe 2+ forms a series of charge-transfer salts with anionic donors such as bromide, iodide, thiocyanate, tricyanomethide, tetraphenylborate and tetracarbonylcobaltate. X-Ray crystallography of the 1:2 tricyanomethide salt identifies the structural origin of the charge-transfer interaction for the contact ion pair, [(HMB) 2 Fe 2+ , C(CN) 3 − ]. The strong carbonylmetalate donors Co(CO) 4 − and Mn(CO) 5 − promote the catalytic de-ligation of bis(arene)iron(II) by the electron-transfer chain (ETC) process previously identified in electrochemical and photochemical studies.

This paper deals with the results of a comparative investigation of electronic and structural aspects of degradation of sandwich structures including films of a-Nb2O5 and a-Ta2O5 (where “a” stands for “amorphous”). Experimental data show that the reason for the difference in the degradation processes in such sandwich structures lies in some kinetic factors, such as different ratios of the rates of oxygen diffusion within the volume of the constituent layers and the rates of redox reactions taking place at the inter-layer boundaries. A model of the structural consequences of degradation is offered, explaining the observed transformations of the electric properties of the sandwich structures under consideration.