Norbornadiene complexes of transition metals

Conclusions Correlations were established between the stereochemistry of 2-(-carbinol)norbornadiene complexes of rhodium and their mass spectra.This study is also communication 30 from the series Mass Spectrometry of Transition Metal- Complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2701–2703, December, 1982.     

Norbornadiene complexes of transition metals 1. Synthesis of Rh(η4-C7H8)(η5-C5H5) derivatives with functional substituents in the diene ligand

Conclusions New rhodium complexes, derivatives of Rh( ⁴-C₇H₈)(acac) and Rh( ⁴-C₇H₈)( ⁵-C₅H₅) with functional groups in the norbornadiene ligand, have been synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1124–1127, May, 1981.     

Lewis-Base Adducts of Group 11 Metal(I) Compounds. LXXVI Structural Studies in the Copper(I) Halide : Norbornadiene System

The structural characterizations of some copper(I) halide (CuX) adducts with norbornadiene (nbd) are recorded. CuCl : nbd (1:1)₄ (a redetermination), (2:1)_2(|), are systems both based around Cu₄Cl₄ cubane-type cluster arrays. CuBr : nbd (7:3)_(|)( 0.5 MeOH), a complex polymer with 3-symmetry, is believed to be the complex previously described as an adduct of 2:1 stoichiometry. Attempts to obtain an iodide counterpart have resulted in the definition of an ephemeral adduct CuI : MeCN (3:2)_(|). 0.5 C₇H₈ in which, remarkably, the nbd is uncoordinated; the complex is a polymer, related to the [AgX(quinoline)]_(|) (X = Cl, Br) saddle polymer.     

Two-Step Synthesis of Heptacyclo[6.6.0.02,6.03,13.04,11.05,9.010,14] tetradecane from Norbornadiene: Mechanism of the Cage Assembly and Post-synthetic Functionalization

A selective and scalable two-step approach to the dimerization of norbornadiene (NBD) into its thermodynamically most stable dimer, heptacyclo[6.6.0.0^2,6.0^3,13.0^4,11.0^5,9.0^10,14] tetradecane, (HCTD) is reported. Calculations indicate that the reaction starts with the Rh-catalyzed stepwise homo Diels–Alder cyclisation of NBD into its exo-cis-endo dimer. Treatment of this compound with acid promotes its evolution to HCTD via a [1,2]-sigmatropic rearrangement. The assemblies of 7,12-disubstituted cages from 7-(alkyl/aryl) NBDs, as well as the selective post-synthetic C−H functionalization of the core HCTD scaffold at position C1, or positions C1 and C4 are described.     

Role of the paramagnetic nickel(I) complex in the catalytic dimerization of norbornadiene

In a joint investigation of the kinetic laws of the catalytic cyclodimerization of norbornadiene in the presence of bis-³-allyl complexes of nickel by gas chromatography and ESR, a definite correspondance in the change in the concentrations of norbornadiene, its dimers, and the paramagnetic nickel(I) complex was detected. The absence of an ESR signal in model systems, as well as the substantial differences in the relative amounts of Ni(I) when bis-₃ -allyl nickel complexes of different structure were used, suggests that paramagnetic Ni(I) does not participate as one of the intermediates in the catalytic process.M. V. Lomonosov Moscow Institute of Fine Chemical Technology. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 4, pp. 513–516, July–August, 1991. Original article submitted October 16, 1989.     

Stannylation of unsaturated carbon-carbon bonds by tin tetrachloride

The reactions of tin tetrachloride and four terminal alkynes (PhCCH, ^tBuCCH, ⁿBuCCH, HOCH₂CCH), norbornene, and norbornadiene in dichloromethane or chloroform solution lead to the formation of stannylation products, which were characterized by ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. Virtually complete α-regioselectivity was obtained in reaction of all four alkynes without any effect of the relative steric bulk of the substituent R at the triple bond of alkyne RC_βC_αH. The reaction of norbornene and norbornadiene with SnCl₄ is stereoselective, giving an exo stannylation product.     

Orthogonal Photoswitching with Norbornadiene

Orthogonal photoswitching is a convenient but challenging way of controlling multiple functions in a system by selective photoisomerization of one unit before the other in any arbitrarily chosen sequence. Here, we present this concept for the norbornadiene/quadricyclane (NBD/QC) photo/thermo-switch in the presence or absence of a coordinated metal ion. Thus, introducing two pyridyl ligands via ethyne-1,2-diyl bridges provides a system that by chelation of metal ions, such as Pd^II, has altered optical and switching properties. Mixing the Pd^II complex with its free ligand furnishes a four-state system where NBD-to-QC photoisomerizations for complexed and uncomplexed species are controlled by the irradiation wavelength and can occur orthogonally, that is, the sequence of photoisomerizations can be swapped. Studies on Ag^I and Pb^II complexes, being less stable than the Pd^II complex, are also presented; these exhibit like the Pd^II complex significantly red-shifted NBD absorptions.     

Formation of closo-rhodacarboranes containing η2,η3-(CH2=CHC5H6) ligand in the reaction of μ-dichloro-bis[(η4-norbornadiene)rhodium] with nido-dicarbaundecaborates [K][nido-7-R1-8-R2-7,8-C2B9H10]

The reactions of a complex [(⁴-C₇H₈)RhCl]₂ (C₇H₈ is norbornadiene) with salts of substituted nido-dicarbaundecaborates, [K][nido-7-R¹-8-R²-7,8-C₂B₉H₁₀] (R¹ = R² = H (a); R¹ = R² = Me (b); R¹, R² = 1,2-(CH₂)₂C₆H₄ (c); R¹ = Me, R² = Ph (d)), in CH₂Cl₂ afforded new closo-(²,³-(4-vinylcyclopenten-3-yl))rhodacarboranes. The structures of the compounds were studied by multinuclear NMR spectroscopy. A probable mechanism of the rearrangement of the norbornadiene ligand is discussed.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1875–1878, September, 2004.     

Effect of the Formation of Inclusion Complexes With β-Cyclodextrin on the Photoisomerization and Fluorescence Properties of Aromatic Norbornadiene Derivatives

The valence photoisomerization of four aromatic norbornadiene (NBD)derivatives has been studied in ethanol and in 0.01 M -cyclodextrin(-CD) water–ethanol (v/v, 99/1) solution (WECD). Observedfirst-order rate constants are found to be of the same order of magnitude inethanol and WECD, ranging between 0.1 and 0.28 s^-1, accordingto the compound. These photoisomerization kinetic properties are attributedto the formation of inclusion complexes between NBDs and -CD. Thestoichiometry is 1 : 1, and association constants ranging between 310 and390 M^-1 have been determined fluorimetrically, usingBenesi–Hildebrand plots and a nonlinear regression method. Thestructure of the inclusion complexes is discussed on the basis of AMIsemiempirical dimension calculations and photophysical properties.     

Synthesis of new types of tetracyclo[4.3.0.02,4.03,7]nonane hydrocarbons by cyclocodimerization of norbornadiene and its derivatives with diacetylenes and vinylacetylenes,catalyzed by low-valence cobalt complexes

Conclusions Three-component complex cobalt-containing catalysts are proposed, which are activated by PPh₃ or by an excess of acetylenic hydrocarbons, with which cyclocodimerization of norbornadiene or spiro{bicyclo[2.2.1]hepta-2,5-diene-7,1-cyclopropane} with diacetylenes can be carried out leading to derivatives of the bitetracyclo[4.3.0.0^2,4.0^3,7]nonane series in high yields.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1061–1067, May, 1987.     

Low Molecular Weight Norbornadiene Derivatives for Molecular Solar‐Thermal Energy Storage

Molecular solar‐thermal energy storage systems are based on molecular switches that reversibly convert solar energy into chemical energy. Herein, we report the synthesis, characterization, and computational evaluation of a series of low molecular weight (193–260 g mol^?1) norbornadiene–quadricyclane systems. The molecules feature cyano acceptor and ethynyl‐substituted aromatic donor groups, leading to a good match with solar irradiation, quantitative photo‐thermal conversion between the norbornadiene and quadricyclane, as well as high energy storage densities (396–629 kJ kg^?1). The spectroscopic properties and energy storage capability have been further evaluated through density functional theory calculations, which indicate that the ethynyl moiety plays a critical role in obtaining the high oscillator strengths seen for these molecules.     

Cooligomerization of 1,2-dienes with norbornadienes catalyzed by cobalt complexes

Conclusions Under the action of low-valency cobalt complexes [2 + 2 + 2] cycloaddition of allene, cyclopropylallene, phenylallene, and 1,2-cyclononadiene to norbornadiene and spirocyclo-[2.2.l]hepta-2,5-diene-7,1-cyclopropane takes place with the formation of derivatives of tetracyclo[4.3.0.0^2,4. 1.0^3,7] nonane in high yields.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1346–1356, June, 1988.     

Reactions of alkenesulfenamides with olefins in the presence of POHal3

A new method for the synthesis of ,"-dihaloalkyl vinyl sulfides was proposed. The method is based on reactions of alkenesulfenamides with olefins in the presence of POCl₃ or POBr₃. The reactions with cage olefins (norbornene, norbornadiene, camphene, and dimethyl 5,6-di-endo-norbornenedicarboxylate) afford stable products, while vinylsulfenylation of a conformationally labile olefin (cyclohexene) give products that decompose during their isolation.     

Synthesis and structure of N-heterocyclic carbene complexes of rhodium and iridium derived from an imidazolium-linked cyclophane

This paper describes the synthesis, spectroscopic and structural characterisation, and electrochemical behaviour of some rhodium and iridium complexes of the form LM(X₁)(X₂)⁺, where L is a chelating bis(carbene) derived from an imidazolium-linked ortho-cyclophane. The complexes where X₁/X₂ = 1,5-cycooctadiene or norbornadiene were prepared from the imidazolium-linked cyclophane and the appropriate metal source. In these complexes, the M-L bonding was quite robust, but the diene could be displaced by CO to give the dicarbonyl complexes , from which one or both carbonyl ligands could be displaced by monodentate or bidentate phosphines, respectively. Structural studies revealed only minor variations in the cyclophane unit upon exchange of the ancillary ligands, in each case the rhodium complex being isomorphous with its iridium analogue. In cyclovoltammetric studies of LRh(dppe)⁺, reversible Rh(I/II) and Rh(II/III) redox couples were observed. The other rhodium complexes displayed more complex electrochemical behaviours and did not undergo simple reversible redox reactions.     

Sigmatropic Rearrangements Accompanying the Addition of Dichlorocarbene to Norbornadiene

A new product arising from the reaction of dichlorocarbene with norbornadiene, 6endo-(2,2-dichlorovinyl)-cis-bicyclo[3.1.0]hex-2-ene, is described. It does not arise from the normal exo-l,2-adduct, but possibly originates by sigmatropic rearrangement of an initially formed zwitterionic intermediate.     

Ring opening metathesis polymerisations of norbornene and norbornadiene derivatives containing oxygen: a study on the regeneration of Grubbs catalyst

Ring opening metathesis polymerisation (ROMP) of norbornene and norbornadiene derivatives containing oxygen are investigated using Grubbs well-defined ruthenium initiator. A series of 7-alkoxy norbornadiene monomers (2b-d), containing alkoxy groups with decreasing steric hindrance in the 7-position have been prepared. The ROMP reactions of monomers showed that as the reaction proceeds the initiator is consumed first and then is partially regenerated at the expense of the propagating species. A small amount of another carbene species X, giving a broad signal at 17.44 ppm, is also formed which is extremely stable in solution. The species X is an active metathesis species and is able to perform ROMP on strained cyclic olefins. ROMP of monomers without alkoxy groups in the 7-position (3, 4a, 4b, 5a and 5b) and also monomers with alkoxy groups in the 5 and/or 6 positions of norbornene (6 and 7) have been performed under similar conditions. None of these systems exhibited regeneration of the initiator and no resonances due to species X can be seen in the ¹H NMR spectra. The results confirm that the presence of oxygen in the 7-position of the norbornadiene monomer plays an important role in the process of regeneration of the initiator. It is found that the steric bulk and the position of substituents of the monomer have a pronounced influence on the extent of regeneration of the initiator.     

Molecular enthalpies: 1. Ground-state thermodynamic and computed enthalpies of the norbornadiene cycle

The enthalpies of formation of norbornadiene, norbornene, norbornane, nortricyclane, and quadricyclane, which are experimentally known, have been calculated using the semiempirical programs MNDO, AM1, and PM3 and the empirical force-field method MMP2. MMP2 agrees most closely with experimental results. Of the semiempirical methods, PM3 agrees most closely with experimental results and is very good for the alkenes. Enthalpies of hydrogenation, calculable fromH _f, are inconclusive on the question of ground-state homoaromatic stabilization of norbornadiene.