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Tris(pentafluorophenyl)borane reacts with 9,9-dipropargylfluorene (5) in a 2:1 ratio under ambient conditions to yield a statistical mixture of the double-1,1-carboboration products (Z,Z)-, (E,Z)-, and (E,E)-6. Photolysis of the product mixture yields a new mixture that is substantially enriched in the (Z,Z)-6isomer. Treatment of 5with the P(o-tolyl)3/B(C6F5)3frustrated Lewis pair gave the zwitterionic eight-membered heterocycle 7a, which is the product of a 1,1-carboboration of one alkynyl unit followed by an intramolecular 1,2-addition of the in situ generated new FLP to the remaining alkynyl moiety. The reaction of the PtBu3/B(C6F5)3FLP gave an analogous result, yielding 7b. Treatment of 1,2-diethynylbenzene (9) with the PtBu3/B(C6F5)3FLP resulted in deprotonation, forming the phosphonium/alkynylborate salt 10. The reaction of triarylphosphine/B(C6F5)3pairs using the phosphines P(o-tolyl)3and P{Ph2[2,5-bis(trifluoromethyl)phenyl]} resulted in clean 1,2-P/B FLP additions to a CC triple bond to yield the products 11and 12, respectively. Eventually, the reaction of 9with the poorly nucleophilic phosphine P(C6F5)3in combination with B(C6F5)3gave the zwitterionic product 14, which is thought to result from a two-step reaction involving 1,1-carboboration followed by an exo-dig cyclization by means of a 1,2-P/B FLP reaction of the in situ generated alkenylborane Lewis acid and P(C6F5)3to the remaining alkynyl unit. The products (Z,Z)-6, 7a,b, 10, 12, and 14were characterized by X-ray crystal structure analyses. [ABSTRACT FROM AUTHOR]

Treatment of the α-dimethylamino[3]ferrocenophane derivative 3with n-butyllithium results in a directed o-metalation at the adjacent Cp ring of the ferrocene unit to selectively yield the ( R*, R*, p- S*) diastereomer 4. Similarly, lithiation of rac- 12gives ( R*, p- S*)- 13. Both these compounds form meso-type dimers in the crystal that feature a central C 2Li 2four-membered-ring moiety. Compound 13crystallizes with excess n-butyllithium to form a ( 13· n-BuLi) dimer that was also characterized by X-ray diffraction. Directed lithiation of the nonbridged ferrocene derivative 1-(dimethylaminobenzyl)ferrocene ( 16) with tert-butyllithium resulted in an opposite stereoselectivity to yield ( R*, p- R*)- 17, which forms a chiral dimeric structure in the solid state, as was revealed by its X-ray crystal structure analysis. [ABSTRACT FROM AUTHOR]

The first organometallic cadmium hydroxylamide [Cd(MeCd) 4(ONEt 2) 6] ( 1) has been prepared by alkane elimination from dimethylcadmium upon treatment with N, N-diethylhydroxylamine and characterized by variable-temperature NMR spectroscopy ( 1H, 13C, 113Cd), single-crystal X-ray diffraction, and elemental analysis. In the solid state compound 1comprises an Cd 5N 6O 6backbone with a central octahedral coordinate Cd atom, while all 12 donor atoms are attached to the 5 Cd nuclei whereas in solution it is of highly dynamic nature. [ABSTRACT FROM AUTHOR]

“Markovnikov” hydroboration of bis(pentafluorophenyl)(propynyl)phosphine (12) with Piers' borane [HB(C6F5)2] gives the frustrated Lewis pair (FLP) (C6F5)2P–(μ-CCHCH3)–B(C6F5)2(13) as the major product in good yield. FLP 13adds cleanly to 1-alkynes to form the five-membered heterocyclic products 15(two examples). It adds to the CN double bond of arylisocyanates to yield the five-membered heterocycles 16(two examples), and it regioselectively adds to aldehydes to yield the B–O/P–C bonded heterocycles 17(from benzaldehyde) and 18(from trans-cinnamic aldehyde), respectively. Dynamic 19F NMR spectroscopy indicates a rapidly occurring reversible P–C bond dissociation process taking place in 17and 18[17: ΔG⧧diss(328 K) = 14.7 ± 0.3 kcal/mol; 18: ΔG⧧diss(368 K) = 11.9 ± 0.2 kcal/mol]. The products 15a, 15b, 17, and 18were characterized by X-ray diffraction. This chemistry indicates that frustrated Lewis pair behavior can be induced electronically by the choice of suitable substituents at the Lewis base. [ABSTRACT FROM AUTHOR]

o-Vinyl/α-NRR′-substituted [3]ferrocenophane derivatives (R = R′ = Me (8), R = H, R′ = tBu (11), R = R′ = H (13)) were prepared via a Wittig olefination route starting from the corresponding aldehyde. The NMe2group was further exchanged for Pmes2(9). The bulky α-substituents NHtBu and Pmes2form frustrated Lewis pairs with B(C6F5)3that undergo cooperative intramolecular addition reactions to the adjacent alkene. In the case of 13stable Lewis pair adduct (14) formation is observed instead. The corresponding α-dimesitylphosphino[3]ferrocenophanyl-substituted butadiene (16) and acrolein (23) derivatives were synthesized via multistep synthetic pathways. Upon treatment with B(C6F5)3, intramolecular 1,4-addition of the frustrated Lewis pairs to the adjacent doubly unsaturated moieties takes place to yield the zwitterionic products 17and 24, respectively. The complexes 9, 10, 12, 16, 17, 20, 22, and 23were characterized by X-ray diffraction. [ABSTRACT FROM AUTHOR]

Strongly electrophilic boranes R-B(C6F5)2react readily with a variety of 1-alkynes by means of a 1,1-carboboration reaction to yield alkenylborane products, which can subsequently be used as reagents in metal catalyzed cross-coupling reactions. [ABSTRACT FROM AUTHOR]

Treatment of the [3]ferrocenophane cyanide trans-7with strong aqueous base led to a diasteromeric mixture of carboxylic acids trans-8/cis-8in a 1:2.8 ratio. Analogous base-induced hydrolysis of the related ortho-bromine-substituted [3]ferrocenophane nitrile trans-12selectively yielded the cis-carboxylic acid cis-13. DFT calculations showed that in this series the cis-carboxylic acids are thermodynamically more stable than the respective trans-isomers. The dicarboxylic acid cis-15was prepared in a similar reaction sequence and used for further synthesis of a “TADDOL-analogous” [3]ferrocenophane (cis-20). [ABSTRACT FROM AUTHOR]

A series of α,β-unsaturated amides of pyridine and naphthyridine (1−4) derived from trans-cinnamic acid and its derivatives has been synthesized. The hydrogen-bonding behavior of these simple amides in the solid state has been established by solving X-ray structures. In solution and in the solid state, the above compounds 1−4were found to bind carboxylic acid utilizing both conventional and unconventional hydrogen bonds. Hence, the possibility has been revealed of using this motif as an alternative of urea for the design of task-specific hosts. The experimental results have been rationalized with an accompanying theoretical study involving density functional calculations on the structure and the relative energies of different rotamers of the host systems as well as the binding energy of the complexes formed with trans-cinnamic acid. Generally, small binding energies (0.58−0.70 eV) are calculated for the complexes in the gas phase which become even smaller in chloroform solvent. [ABSTRACT FROM AUTHOR]

Condensation of allylcyclopentadiene 1with acetone in the presence of pyrrolidine gave 2-allyl-6,6-dimethylfulvene (2). Methyllithium addition gave lithium 1-allyl-3-tert-butylcyclopentadienide (3). Transmetallation with 0.5 equiv. of ZrCl4yielded the respective functionalized zirconocene dichloride complexes meso-4and rac-4, which were both isolated isomerically pure. With 10 mol% of [Cl2(PCy3)2RuCHPh] the rac-4diastereoisomer underwent a clean intramolecular ring-closing olefin metathesis reaction to yield the ansa-zirconocene complex rac-6. The complexes meso-4, rac-4and rac-6were characterized by X-ray diffraction. Treatment of the open metallocenes meso-4and rac-4, respectively, with excess methylalumoxane gave rather active ethene polymerization catalysts. The corresponding catalyst derived from the conformationally restricted bulky ansa-metallocene rac-6is markedly less active. [ABSTRACT FROM AUTHOR]

Treatment of 6-dimethylaminofulvene 1with lithio-2,6-diisopropylanilide 2gave the lithiated 6-(2,6-diisopropylanilido)fulvene 3. Its treatment with Me3SiCl afforded the N-silylated derivative (C5H4)CH-N(Ar)SiMe3(4), which was characterized by X-ray diffraction. Protonation of 3was effected by treatment with acetylacetone to yield a mixture of syn- and anti-5[(C5H4)CH-N(Ar)H] contaminated with some 2,6-diisopropylaniline. The minor isomer, syn-5, was also characterized by an X-ray crystal structure analysis. Treatment of this mixture with Zr(NMe2)4led to in situ deprotonation and formation of complex [(C5H4)-CHNAr]2Zr(NMe2)2(6) in a mixture with the exchange product [(C5H4)-CHNAr]2Zr(NMe2)(NH-Ar) (7) as a minor component (both characterized by X-ray diffraction). The corresponding reaction with the reagent Zr(benzyl)4or Cl2Zr(NMe2)2(THF)2resulted in the clean formation of the products [(C5H4)-CHNAr]2Zr(benzyl)2(8) (also characterized by X-ray diffraction) and [(C5H4)-CHNAr]2ZrCl2(9), respectively. Complex 9was subjected to a “metal-free” catalytic hydrogenation reaction by treatment with a substoichiometric amount of B(C6F5)3under mild conditions (2 bar H2, rt) to yield the product [(C5H4)-CH2-NH-Ar]2ZrCl2(10), which was also characterized by an X-ray crystal structure analysis. Treatment of 9with 1 or 2 molar equiv of B(C6F5)3gave “frustrated” Lewis pairs that split dihydrogen heterolytically at near to ambient conditions to give the salts {[(C5H4)-CH2NH2+Ar][(C5H4)-CH2NHAr]}ZrCl2/[HB(C6F5)3−] (11) and [(C5H4)CH2NH2+Ar]2ZrCl2/2 [HB(C6F5)3−] (12), respectively. The system 12itself was shown to be an active catalyst for the hydrogenation of bulky imines and of a bulky silyl enol ether. [ABSTRACT FROM AUTHOR]

The investigation of the electronic and steric properties of 4,5-disubstituted imidazolylidenes is reported, as well as their successful application as organocatalysts in the formation of γ-butyrolactones by conjugate Umpolung. [ABSTRACT FROM AUTHOR]

Deprotonation of 6-dimethylamino-6-methylpentafulvene (3a) with methyl lithium yielded the (1-dimethylaminoethenyl)Cp lithium reagent 4a. Its treatment with zirconium tetrachloride under carefully controlled reaction conditions gave the corresponding bis(enamino-Cp)ZrCl2complex 5a. The product 5ais very sensitive to acid-catalyzed Mannich condensation. Photolysis of 5a(HPK 125, Pyrex filter) resulted in a rapid intramolecular [2+2]cycloaddition reaction to yield the cis-bis(dimethylamino)cyclobutylene-bridged ansa-zirconocene complex 7ain a photostationary equilibrium (5a:7a≈ 30:70). After acid-catalyzed Mannich conversion of the minor component (5ato 6a) the new photoproduct 7awas isolated pure by fractional crystallization. The complexes 5aand 7awere both characterized by X-ray diffraction. [ABSTRACT FROM AUTHOR]

New triphenylamine-based chemosensors for selective recognition of dicarboxylic acids have been designed and synthesized. They are variants of previously synthesized chemosensors, offering different possibilities for selective recognition of dicarboxylic acids. Theoretical calculations by density functional theory and time dependent density functional theory have been carried out on these as well as on one of the previously reported systems and on complexes formed by the triphenylamine based chemosensors and aliphatic dicarboxylic acids of different chain-lengths. Carboxylic acid binding takes place through charge-neutral pyridyl amide receptor sites with concomitant quenching of fluorescence of the triphenylamine moiety. The theoretical results are consistent with the experimental and correlation is found between the calculated binding energies and the experimental binding constants. [ABSTRACT FROM AUTHOR]

A series of 6,8-diazabicyclo[3.2.2]nonane derivatives bearing two aromatic moieties was prepared, the affinity toward σ1and σ2receptors was investigated, and the growth inhibition of six human tumor cell lines was determined. The enantiopure bicyclic ketones 5a((+)-(1S,5S)-6-allyl-8-(4-methoxybenzyl)-6,8-diazabicyclo[3.2.2]nonane-2,7,9-trione) and 5b((+)-(1S,5S)-6-allyl-8-(2,4-dimethoxybenzyl)-6,8-diazabicyclo[3.2.2]nonane-2,7,9-trione) as well as their enantiomers ent-5aand ent-5bserved as chiral building blocks, which were derived from (S)- and (R)-glutamate, respectively. Structure−affinity relationships revealed that 11a(Ki= 154 nM), ent-11a(Ki= 91 nM), and ent-17a(Ki= 104 nM) are the most potent σ1ligands. High σ2affinity was achieved with 17b(Ki= 159 nM) and 8b(Ki= 400 nM). The bicyclic σ ligands showed a selective growth inhibition of the small cell lung cancer cell line A-427 with the benzyl ethers 11and the benzylidene derivatives 17being the most potent compounds. 11ahas a cytotoxic potency (IC50= 0.92 μM), which exceeds the activity of cisplatin and interacts considerably with both σ1and σ2receptors. [ABSTRACT FROM AUTHOR]

An unprecented dimeric capsular assembly of a tetramethylated C-hexyl resorcinarene and an expected one from unsubstituted C-butyl resorcinarene with tetramethylammonium cation are described. Surprisingly tetramethylated C-hexyl resorcinarene, with no apparent possibility for intra-capsular hydrogen bonds, forms a capsule which is held together solely by the cationπ interactions and the complementary geometry of the spherical guest cation and the concave resorcinarene host. The C-butyl resorcinarene capsule, as in the case of dimeric resorcinarene capsules reported earlier, is mediated viasolvent molecules and intra-capsular hydrogen bonds. We also report here two co-crystals of C-methyl resorcinarene and one of C-(3-hydroxy)propyl resorcinarene with R2,R′2-type of alkyl ammonium halide salts. These structures manifest the difficulty of structure control and prediction due to competing and multiple interactions in the crystalline state. The design of the resorcinarene-based host–guest system so as to enable prediction or inducement of a specific crystal packing or structural arrangement of host and guest, is very difficult, if not impossible due to the cameleon nature of resorcinarenes in their ability to form weak interactions. [ABSTRACT FROM AUTHOR]

Hydroboration of (COD)Rh(η 5-C 5H 4-allyl) ( 7) with the strongly electrophilic reagent HB(C 6F 5) 2yields (COD)Rh[η 5-C 5H 4-(CH 2) 3B(C 6F 5) 2] ( 8). Nucleophilic N-heterocyclic reagents (1-methylimidazole or 1-methylbenzimidazole) add to the boron atom of the bifunctional complex to yield the respective adducts ( 9a, 9b). Both were characterized by X-ray diffraction. Addition of HB(C 6F 5) 2to the corresponding (COD)Ir(η 5-C 5H 4-allyl) complex ( 10) eventually results in the formation and isolation of the cycloborylated zwitterionic (COD)(η 5-C 5H 3- cyclo-(CH 2) 3B(C 6F 5) 2]IrH product ( 13) (also characterized by X-ray crystal structure analysis). However, 13seems to thermally equilibrate in a reverse electrophilic aromatic substitution reaction with the thermodynamically disfavored open-chain (COD)Ir[η 5-C 5H 4-(CH 2) 3B(C 6F 5) 2] isomer ( 11). This follows from reactions of 13with 1-methylimidazole or 1-methylbenzimidazole, which rapidly yield the corresponding open-chain adducts 14aand 14bat room temperature (both characterized by X-ray diffraction). In a slow reaction complex 13even eventually reacts with pyrrole by ring opening to yield the open-chain product 15, which features the 2 H-pyrrole isomer coordinated to the strong −B(C 6F 5) 2Lewis acid at the end of the trimethylene tether. Complex 15was also characterized by an X-ray crystal structure analysis. [ABSTRACT FROM AUTHOR]

Synthetic routes to alkali metal cyclopentadienides that bear various organic functional groups on their five-membered carbocyclic ring systems are presented and discussed using selected examples. These include carbonyl addition reactions of cyclopentadienides to, for example, alkyl isocyanates to eventually yield carboxamide-substituted cyclopentadienide systems. These and related routes have been used to, for example, prepare peptide-substituted Cp anions. Fulvene routes are very useful for the synthesis of alkenylcyclopentadienides, of imino-Cp compounds, of aminomethyl- or phosphinomethyl-Cp derivatives, and even their respective dianionic analogues. Many of the new functionalized lithium cyclopentadienide examples were structurally characterized. Many of them form well-defined extended oligomeric structures that make specific use of the functional groups in the construction of the supramolecular complex framework. Eventually, first examples of specific carbon−carbon coupling reactions are presented and discussed that take place at the active lithium cyclopentadienide stage, which may lead to the development of a selective functional group chemistry at the alkali metal cyclopentadienides. [ABSTRACT FROM AUTHOR]

Deprotonation of alkynyl imines 1with LDA at low temperature and subsequent transmetalation with copper thiophenolate gives the annulated azepines 11a−iin 41−73% yield after aqueous workup. The key step of the reaction is a copper-mediated intramolecular nucleophilic attack at the triple bond. [ABSTRACT FROM AUTHOR]

β-Fluoroalkylated enones are efficient dienophiles in Diels-Alder cycloadditions to prepare various fluorinated cylic compounds. However, the presence of the fluoroalkyl moiety modifies the reactivity and the selectivity of these cycloadditions. [ABSTRACT FROM AUTHOR]

The extension of Robson-type ligands from dinucleating based on 2,6-diformylphenol to trinucleating based on 2,7-diformyl-1,8-naphthalenediol is demonstrated by the synthesis, structural and magnetic characterization of the first trinuclear CuII complex using a 1,8-naphthalenediol derived ligand. [ABSTRACT FROM AUTHOR]

The enantioselective alkylation of α,β-unsaturated aldehydes with stabilized carbocations as electrophiles via the activation as dienamine intermediates is described. This unique application of dienamine catalysis allows for the first enantioselective γ-alkylation of linear α,β-unsubstituted enals. [ABSTRACT FROM AUTHOR]

Hydroboration of dimesitylvinylphosphine with Piers’ borane [HB(C6F5)2] gives the ethylene-bridged intramolecular frustrated P/B Lewis pair 1. It adds pyridine, tert-butyl isocyanide or pivalonitrile to the strongly electrophilic boron center to yield the respective adducts 5–7. Compound 1undergoes a 1,1-phosphine/borane addition to the terminal nitrogen center of phenyl azide to yield the five-membered heterocycle 8, featuring a pendant –NN–Ph. This can be regarded as a boron-stabilized intermediate of a Staudinger reaction. Benzaldehyde and phenyl isocyanate undergo 1,2-P/B additions of 1to their reactive carbonyl groups to yield the corresponding six-membered heterocycles 9and 10, respectively. The P/B Lewis pair reacts with nitrosobenzene by 1,2-addition to the –NO unit under P–N and O–B bond formation to give the six-membered heterocycle 11. The compounds 5–11were characterized by X-ray crystal structure analyses. [ABSTRACT FROM AUTHOR]

Reaction of [RuCl(Cp)(PPh3)2] with bis[di(2-fluorophenyl)phosphino]benzene, 3, yields complex [RuCl(Cp)(3)], [4]. The chloro ligand in [4] can be exchanged for the 2-azidoethyl isocyanide ligand 2, giving complex [Ru(Cp)(2)(3)]Cl, [5]Cl, which reacts with NH4BF4to give [5]BF4. The azido group of the coordinated isocyanide ligand in [5]Cl or [5]BF4can be reduced with Zn/NH4Cl/H2O to give the complex with the 2-aminoethyl isocyanide ligand. This ligand is not stable but cyclizes by an intramolecular nucleophilic attack of the amino group at the isocyanide carbon atom to give an NH,NH-stabilized NHC ligand in complexes [6]X (X = Cl, [6]Cl; X = 0.5 ZnCl4, [6]2(ZnCl4); X = BF4, [6]BF4). Deprotonation of the NH,NH-stabilized NHC ligands in cations of type [6]+leads to an intramolecular nucleophilic attack of the amido nitrogen atoms at the fluorinated phenyl groups of the diphosphine ligand under formation of the complex with the faciallycoordinated macrocyclic [11]ane-P2CNHCligand [1]X (X = Cl, [1]Cl; X = 0.5 ZnCl4, [1]2(ZnCl4); X = BF4, [1]BF4). Formation of the macrocycle is facilitated by the steric pressure excerted by the cyclopentadienyl ligand. The molecular structures of [4], [5]BF4, [6]BF4·CH2Cl2, and [1]Cl·CH2Cl2·0.5H2O have been determined by X-ray diffraction. [ABSTRACT FROM AUTHOR]

Bis-acylhydrazones of 2,6-pyridinedicarbaldehyde are introduced as planar pentadentate ligands for the coordination of lanthanide(iii) ions. With large cations (e.g.lanthanum(iii)) 1 : 1 as well as 2 : 1 ligand-to-metal complexes are formed depending on the stoichiometry of the reaction. The different complexes are distinguished by NMR spectroscopy and ESI MS in solution and they can be characterized by X-ray diffraction. With the small lutetium(iii) ion only the 1 : 1 complex is formed. In the 1 : 1 compounds, anions such as nitrate fill up the coordination site at the metal ion. However, in some cases anion substitution by solvent molecules is observed in the solid state leading to cationic and even dicationic coordination compounds. [ABSTRACT FROM AUTHOR]

A series of benzobisimidazolium salts 1a–dhas been prepared by tetraalkylation of benzobisimidazol. The salts 1a–dreact with two equivalents of [Pt(Cl)2dppe] in the presence of 2.2 equivalents of sodium acetate to yield the dinuclear biscarbene complexes 2a–d. Under the same reaction conditions, the benzobisimidazolium salts react with only one equivalent of [Pt(Cl)2dppe] and one equivalent of sodium acetate to yield the monometalated carbene/benzimidazolium derivatives 3a,3c. Benzobisimidazolium salt 1creacts with two equivalents of nickelocene to give the biscarbene bridged dinuclear nickel complex 4. Treatment of 4with two equivalents of 4,4′-bipyridine leads to the formation of the CpNiII-cornered molecular rectangle 5. [ABSTRACT FROM AUTHOR]

The hydroquinoid phenanthrene Cr(CO)3complex 1, directly accessible from the benzannulation of pentacarbonyl[(methoxy)-1-naphthylcarbene]chromium with 3-hexyne as the kinetically favored isomer, and its thermodynamically stable haptotropomer 2undergo a photoinduced substitution of one CO ligand for phosphines and phosphites PR3(R = Me, OMe, Ph, OPh) to give (η6-phenanthrene)Cr(CO)2PR3complexes 3−10. Upon warming chromium complexes 3−6, a haptotropic metal migration affords regioisomers 7−10in up to 79% yield bearing the chromium fragment coordinated to the terminal unsubstituted phenanthrene ring. The rearrangements have been monitored by IR and NMR spectroscopy. Kinetic NMR experiments in noncoordinating solvents such as hexafluorobenzene reveal first-order kinetics in line with an intramolecular metal shift along the extended π-system. The metal migration can be tuned by the P-based coligand as demonstrated by rate constants differing by 2 orders of magnitude and by barriers of activation differing by 15 kJ mol−1, respectively. A quantitative analysis (QALE) of these ligand effects suggests that the rearrangement is controlled by both electronic and steric properties of the P-coligand. The molecular structures of the complexes 3, 4, and 6−10were established by single-crystal X-ray analysis. Quantum chemical DFT calculations provide a mechanistic rationale of the haptotropic migration in naphthalene and phenanthrene Cr(CO)2PR3complexes. [ABSTRACT FROM AUTHOR]

Hydroboration of allyl(dimesityl)phosphane with HB(C6F5)2gives the intramolecular five-membered P–B Lewis pair 7, that was characterized by X-ray diffraction. Similarly, HB(C6F5)2addition to the substrates (mesityl)2P–CRCH2(R = CH3, Ph) yield the corresponding (mesityl)2P(μ-CHRCH2)B(C6F5)2products 9a(R = CH3) and 9b(R = Ph) that show a weak intramolecular PB interaction. The activation energy of the (reversible) PB cleavage of these substrates was determined by dynamic 19F NMR spectroscopy (9a: ΔG≠inv(280 K) = 11.7 ± 0.4 kcal mol−1). Compounds 9band 9cshow similar values. Compound 9cwas prepared by HB(C6F5)2addition to (mesityl)2P–CHCHSiMe3. Compound 9areacts rapidly with dihydrogen (2.5 bar) at room temperature in pentane to give the zwitterionic H2-activation product (mesityl)2PH+(μ-CHMeCH2)BH−(C6F5)2(11). [ABSTRACT FROM AUTHOR]

Thermal decomposition of Cp2ZrPh2in the presence of the buta-1,3-diynes RCCCCR (R = Ph, SiMe3) can lead to seven- or five-membered metallacycles. In both cases a stable benzo-fused seven-membered zirconacyclocumulene arising from a 2-fold insertion of the triple bonds of the dialkyne in the in situ generated zirconocene benzyne is formed. In the case of Me3SiCCCCSiMe3a second minor complex is isolated: a 3-alkynyl-substituted zirconaindene arising from a β monoinsertion of one acetylenic function of the conjugated diyne in the zirconocene benzyne. No stable 2-alkynyl-substituted zirconacycle was isolated. This α monoinsertion complex is an intermediate in the exchange of the metalated moiety with a main-group atom (e.g., antimony) in a zirconacyclocumulene, explaining the formation of a 2-alkynyl-substituted stibaindene. In the thermal decomposition of Cp2Zr(Me)SCH2R4(R4= Ph, p-MeOC6H4) in the presence of PhCCCCPh, only the α monoinsertion of one triple bond of the diacetylenic reagent in the transient zirconathiirane is observed. The 2-alkynyl-substituted five-membered zirconathiolane is isolated as a bis-sulfonium zirconocene-ate dimer. X-ray diffraction studies corroborate the molecular structure of all these zirconacyclic complexes and stibacycle. [ABSTRACT FROM AUTHOR]

Starting with (S)-aspartate, methyl (S)-2-[1-allyl-4-(4-methoxybenzyl)-3,6-dioxopiperazin-2-yl]acetate 10 was synthesized in a four-step synthesis. Deprotonation of 10 and subsequent trapping of the first cyclization product led to the bicyclic mixed acetal 13 in 15% yield. The low yield of 13, compared with the yield of the corresponding glutamate derivatives, is explained by the higher energy (strain) of the bicyclo[2.2.2]octane system and the lower conformational flexibility of the shorter acetate side chain. The formation of a six-membered Na+-chelate 12 as intermediate is responsible for the high diastereoselectivity of the cyclization step. [ABSTRACT FROM AUTHOR]

Cyclic diamino plumbylenes derived from saturated heterocycles are obtained from deprotonation of diamines and subsequent reaction with PbCl2, or by reaction of a suitable diamine with Pb[N(SiMe3)2]2. Single crystal X-ray studies have been used to probe the solid state structures of a range of these complexes and have shown the fine balance between monomer and dimer formation which is related to the bulk of the organic group attached to the nitrogen atoms. Dimerisation is also shown to effect structural changes within the core of the heterocyclic plumbylene. [ABSTRACT FROM AUTHOR]

Treatment of the α-dimethylamino[3]ferrocenophane system 3with methyl iodide followed by dimesitylphosphine (Mes 2PH) gave the α-(dimesitylphosphino)[3]ferrocenophane 5. This forms a frustrated Lewis pair [ 5/8] with B(C 6F 5) 3( 8) that rapidly reacts with dihydrogen under ambient conditions to probably give the phosphonium cation/hydrido borate anion salt [ 5-H +/H- 8−]. This, however, is unstable under the applied reaction conditions with regard to replacement of the newly formed phosphonium leaving group at the ferrocenophane α-position for hydride from the [HB(C 6F 5) 3−] counteranion to eventually yield the unfunctionalized [3]ferrocenophane product ( 10) and Mes 2PH·B(C 6F 5) 3( 11)both characterized by independent syntheses. Analogously, Ugi’s amine ( 6) was converted to (1-(dimesitylphosphino)ethyl)ferrocene ( 7). The frustrated pair [ 7/8] consumes dihydrogen under similar conditions to yield the reduction products ethylferrocene ( 14) and Mes 2PH·B(C 6F 5) 3( 11). [ABSTRACT FROM AUTHOR]

Directed lithiation followed by quenching with CO 2converted the α-dimethylamino[3]ferrocenophane derivative (6 R,9 R)- 1to the corresponding acid derivative (6 R,9 R, pR)- 2. Subsequent functional group interconversion steps gave (6 R,9 R, pR)- 6in an overall yield of ca. 40% (four steps from (6 R,9 R)- 1), which was employed in the synthesis of an artificial model pentapeptide. [ABSTRACT FROM AUTHOR]

Staudinger reaction of dppm-CN (5) gave the corresponding bis(N-phenylphosphinimino)acetonitrile system (6). Deprotonation with LDA furnished the corresponding anionic ligand 9. Its reaction with [(CO)2RhCl]2 gave the corresponding κ2N,N′-chelate complex 11. X-Ray diffraction revealed a non-planar boat-like conformation of the six-membered chelate ring in the crystal. Treatment of 9 with [(nbd)RhCl]2 gave the six-membered chelate complex 12 which features a different twist-like structure in the solid state, as does 13, which was formed by reacting 9 with [(cod)IrCl]2. [ABSTRACT FROM AUTHOR]

Three salts of phenylenediammonium diperchlorate have been prepared and characterized by X-ray crystallography. Their thermal decomposition has been studied by thermogravimetry (TG), differential thermal analysis (DTA), and explosion delay (DE) measurements. The kinetics of thermal decomposition was evaluated by model fitting and isoconversional methods using TG data. The oxidation−reduction reactions near the surface of thermolysing perchlorates may be responsible for the decomposition followed by explosion. The possible pathways of thermolysis have also been proposed. [ABSTRACT FROM AUTHOR]

The perchlorate complexes of manganese, nickel, and zinc with hexamethylenetetramine (HMTA) of the general formula M(H2O−HMTA−H2O)2(H2O−ClO4)2(H2O)2(where M Mn, Ni, and Zn) have been prepared and characterized by X-ray crystallography. Thermal studies were undertaken using thermogravimetry (TG), differential thermal analysis (DTA), and explosion delay (DE) measurements. The kinetics of thermal decomposition of these complexes was investigated using isothermal TG data by applying isoconversional method. The decomposition pathways of the complexes have also been proposed. These were found to explode when subjected to higher temperatures. [ABSTRACT FROM AUTHOR]

The dilithium compounds Li2Cp-CHR1-NAr12A(R1tert-butyl, Ar1p-anisyl) and Li2Cp-CHR2-NAr22B(R2methyl, Ar2o-anisyl) were synthesized by means of fulvene routes as previously described. Single crystals were obtained from THF/pentane. Both systems feature oligomeric chain structures in the solid state. Compound 2Aexhibits a head-to-tail arrangement of monomeric units with recurring chain-constructing (amide)N-Li-(5-Cp) units whereas 2Bfavors a head-to-head type structure with alternating 5-Cp-Li-5-Cp lithiocene and bis(N,O-chelate)Li building blocks. In each case the remaining Liions are coordinated toward the periphery of the main chain as Li(THF)2(2A) or Li(THF) (2B) solvates. [ABSTRACT FROM AUTHOR]

All possible stereoisomeric alcohols (6-benzyl-8-(4-methoxybenzyl)-6,8-diazabicyclo3.2.2nonan-2-ol) and methyl ethers (6-benzyl-2-methoxy-8-(4-methoxybenzyl)-6,8-diazabicyclo3.2.2nonane) are prepared from (R)- and (S)-glutamate. A Dieckmann analogous cyclization, which makes use of trapping the primary cyclization product with Me3SiCl, generates the bicyclic framework. Stereoselective LiBH4reduction and Mitsunobu inversion establish the configuration in position 2. Enantiomeric alcohols 15(1S,2S,5R) and ent-15(1R,2R,5S) as well as diastereomeric methyl ethers ent-17(1R,2R,5S) and ent-22(1R,2S,5S) display high 1receptor affinity. Cell growth inhibition of the stereoisomeric alcohols and methyl ethers against five human tumor cell lines is investigated. In particular, at a concentration of 20 M the four methyl ethers stop completely the cell growth of the small cell lung cancer cell line A-427, indicating a specific target in this cell line. The IC50-values of methyl ethers ent-17and ent-22are in the range of the antitumor drugs cisplatin and oxaliplatin. Binding assays show that the investigated tumor cell lines express considerable amounts of 1and 2receptors. [ABSTRACT FROM AUTHOR]

The Cp2ZrCl(-1,4-diphenylbutenyne)PX2complexes 7a−P(C6H5)2and 10−P(C6F5)2insert tert-butylisonitrile into the Zr−C(sp2) bond to yield the N-inside 2-iminoacyl zirconocene complexes 13aand 13b. X-ray crystal structure analysis of complexes 13aand 13brevealed the presence of a chiral atropisomeric structure with a torsion angle of 74.8(2)° (13a) and 72.9(6)° (13b), respectively, around the central iminoacyl/alkenyl C(sp2)−C(sp2) bond. In solution an analogous chiral structure is observed. The barrier of interconversion of the enantiomeric atropisomers of 13aand 13bwas determined at G(327K) 14.9 ± 0.3 kcal mol-1(13a) and G(325K) 14.8 ± 0.3 kcal mol-1(13b) by temperature-dependent dynamic NMR spectroscopy. Reaction of 7aand 10with methyllithium followed by treatment with B(C6F5)3gave the corresponding cationic zirconocene complexes 12aand 12b. These complexes took up 2 mol equiv of tert-butylisonitrile to yield the cationic N-inside 2-iminoacyl zirconocene systems 14aand 14bas isonitrile adducts. The cationic complexes 14aand 14bare also axially chiral. The barriers of enantiomerization (G(288 K) 13.1 ± 0.3 kcal mol-1(14a), G(293 K) 13.4 ± 0.3 kcal mol-1(14b)) were also determined by dynamic NMR spectroscopy. [ABSTRACT FROM AUTHOR]

2,3-Dihydroxybenzylic esters with Frechet-type dendritic branches as the alcohol component form, in a hierarchical self-assembly process, disk shaped dendrimers when titanium(iv) and lithium ions are added. [ABSTRACT FROM AUTHOR]

Acylhydrazones of 2,3-dihydroxybenzaldehyde are easily accessible and afford heterodinuclear helicates; the self-assembly is specific when the resulting coordination compounds are neutral in charge. [ABSTRACT FROM AUTHOR]

Three novel 2-carboxamide-8-hydroxyquinoline derivatives wrap helically around trivalent lanthanide ions to form monometallic 3 : 1 complexes possessing strong NIR emission. [ABSTRACT FROM AUTHOR]