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The synthesis and characterization of neutral heteroleptic molecular iridium(III) complexes with (2,4-difluoro)phenylpyridine and different pyridine-1,2,4-triazole ligands are described. The studies have shown high external quantum efficiencies and color points better than the standard for blue iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,[C.sup.2]]picolinate.

A study was conducted to explore the different behaviors of the three zinc alkyls M[e.sub.2]Zn, E[t.sub.2]Zn, and [i.sup.P][r.sub.2]Zn under oxygenation conditions with or without the presence of water. The oxygenated product formed in case of [i.sup.P][r.sub.2]Zn, in presence or in the absence of water is mono-(cubane)- type compound while M[e.sub.2]Zn and E[t.sub.2]Zn nonuniformly form either mono- or bis(cubanes) depending on the presence of water.

Bis(1-methylethenyl-cyclopentadienyl)zirconium dichloride (7a) was prepared by a fulvene route. Photolysis at 0[degrees]C with Pyrex-filtered UV light resulted in a rapid and complete intramolecular [2+2]cycloaddition reaction to yield the corresponding cyclobutylene-bridged ansa-zirconocene dichloride isomer (8a). This is one of the rare examples of an organic functional group chemistry that leads to carbon--carbon coupling at the framework of an intact sensitive group 4 bent metallocene complex. More sterically hindered open metallocenes that bear bulky isopropyl or tert-butyl substituents at their Cp rings in addition to the active 1-methylethenyl functional group undergo the photochemical ansa-metalIocene ring closure reaction equally facile. The metallocene systems used and obtained in this study have served as transition metal components for the generation of active metallocene propene polymerization catalysts. photochemistry | topochemical reaction

An efficient method was developed to activate hydroxyl groups, which avoids the use of toxic reagents and tolerates a wide variety of functional groups. This strategy is applied to the synthesis of functionalised p-methoxyphenyl-protected azetidines, pyrrolidines, and piperidines.

An efficient and rapid synthesis of fluoroalkylated enones, bearing various fluoroalkyl moieties is described. It is concluded that beta-fluoroalkylated enones constitute efficient dienophiles for Diels-Alder cycloadditions and that the presence of the fluorinated moiety both increased the reactivity of these compounds and implied modification of the stereoselectivity.

The eleven-component self-assembly of helicate type complexes, which are formed from six catechol ligands bearing carbonyl groups in their 3-position, two-titanium(IV) (or gallium(III)) ions and three lithium cations. The formation of the compounds represents a hierarchical self-assembly process with a strong interaction between the metals and the catecholates and a weaker binding of the lithium cations which leads to dimerization.

The molecular structures of [Ni (H-4)](sub 2) and [Zn (H-4)](sub 4) are determined by X-ray diffraction. The findings indicate distorted tertrahedral coordination geometry for the zinc (II) ions in an NS(sub 3) coordination sphere.

The synthetic route to the manufacture of bifunctional zirconocene/borane complex is described. This complex was characterized by X-ray diffraction method.

Research has been conducted on the racemates and 2-fluorocycloalkyl N-phenylcarbamates. The biohydroxylation of these compounds with Beauveria bassiana has been investigated and the results indicate the isolation of the diastereoisomeric product mixtures hydroxylated in the 4-position.

The self-assembly of supramolecular structures depends on a subtle interplay of a series of different control mechanisms. The geometric as well as electronic complementarity of the molecular building blocks is crucial for the specific formation of defined supramolecular species. In addition, secondary effects, like templating, also have an important function. The templating ability of different cations in the formation of triple-stranded helicate-type complexes from alkyl-bridged di(8-hydroxyquinoline) ligands is investigated by introduction of alkyl chains of different length as ligand spacers. Hereby a 'size-selectivity' between the cations and the dinuclear helicate-type complexes {[(ligand).sub.3][M.sub.2]} is observed. Large cations support the formation of big dinuclear complexes, whereas small cations are able to template the formation of small complexes.

The first examples of the new 'CpCO'MX2 complexes is prepared. It is shown that the synthetic route developed for the preparation of the first example of a 'CpCN'MX2 catalyst precursor, the complex [Cp-C(=CH2)-NSiMe3]Zr-(NEt2)2, can be applied for an analogous synthetic pathway to a related 'CpCO'MX2 system.

Research has been conducted on the complexes containing functionalized cycloheptatrienyl ligands. The syntheses of the molybdenum complexes which contain linked cycloheptatrienyl-phenolate ligands capable to bind to the metal center are reported.

Research has been conducted on the amidines interactions with tetrazoles. The binding of the tetrazole to the N,N'-diethyl-substituted benzamidine has been investigated via X-ray crystallography, solution NMR methods and electrospray mass spectrometry and the results are presented.

The study of stereoselective carbolithiation of terminally substituted 5-hexynyl carbamates is presented. Experiments include preparation and cyclization of 4-functionalized 5-hexynyl carbamates with different terminal substituents to provide enantiopure substituted alkylidene cyclopentanes.

Research was conducted to examine the bidirectional association of branched noncovalent complexes of tetrazoles and 1,3,5-tris(4,5-dihydroimidazol-2-yl)benzene in solution. A completely planar, C3-symmetrical, hydrogen-bonded molecular that salt-packed along the crystallographic c axis with an interplanar spacing of 3.31 angstrom was observed via an X-ray crystal structure analysis of a model complex with tetrazole. Results illustrate how binding interactions between tetrazoles and tris(imidazoline) led to crystal complexes and how self-assembly was followed by self-association.

The compound rac-(Me2Si(1-indenyl)2)ZrCl2 was treated with (butadiene)magnesium to produce the respective ansa-metallocene (s-cis-eta4-butadiene) complex rac-(dimethylsilylenebis(1-indenyl))(s-cis-eta4-butadiene)zirconium. It reacts with the organometallic Lewis acid B(C6F5)3 to produce the ansa-metallocene-(mu-C4H6)-B(C5F5)3 betaine Me2SiInd2Zr(mu-C4H6)B(C6F5)3 (7) that was characterized by X-ray diffraction. Complex 7 has a distorted (sigma,pi-type) allyl ligand, bonded to zirconium, that has a syn-oriented -CH2B(C6F5)3 substituent.

A simple protonation route has been devised for the first time which makes the formation of hypercoordinated carbon geometries synthetically available inside a (mu-hydrocarbyl)bis(group 4 metallocene) complex framework. Readily available neutral dimetallic (mu-alkenyl)-bis(zirconocene) complexes are used as precursors. The developed hydrocarbyl ligands contain hypercoordinated carbon derived from the distorted square-pyramidal CX5 geometry. Results suggest that the combined features of the two group 4 metallocene units have made the hypercarbon structure stable.

The exposure of metallocene-(conjugated diene)-borate-betaine complexes to the alpha-olefin monomers causes them to turn into active polymerization catalysts. Well designed protection of the incipient metallocene cation that forms part of the betaine system as a whole ensures that these complexes have high kinetic and thermodynamic stability in the dormant precatalyst stage. The internal coordination of a neighbouring (sp2)C-F bond to the electrophilic zirconium centre plays a key role in the protection of the active catalyst system.

Deprotonation of dibenzo-N-tert-butylaminofulvene leads to the (1-azapentadienyl)lithium derivative eta-5-azapentadienyllithium being readily available. The derivative is also obtainable from the mechanistically more complex reaction sequence sparked off by treatment of the aminomethylfluorene derivative 9-(N-tert-butylaminomethyl)-fluorene with suitable bases. There seem to be energetic limits to the Li-1-azapentadienyl bonding interaction of eta-5-azapentadienyllithium.

The reaction of ((eta5:eta1-C5H4CH2CH2OMe)ZrCl2(mu-Cl))2 (1) with several solvents, particularly with water, was studied. The bidentate coordination of the C5H4CH2CH2OMe ligand in 1 was retained chloroform, dichloromethane, benzene, acetone, thf and acetonitrile. The coordination of the ether side chain was reversibly broken in methanol and water. A thf solvate of 1 was structurally analyzed. Reaction of wet DMSO produced the salt ((eta5:eta1-C5H4CH2CH2OMe)ZrCl2(H2O)(DMSO)2)(C) in which the ether side-arm was not coordinated.

A new preparative route to aryl-substituted derivatives of the linear-orthogonal 2-azaalenium ions (2-azoniaalene ions) is reported. X-ray, IR, and NMR data was used to obtain complete structural information about the products obtained. The results are compared with high level ab initio and density functional theory calculations.

The chiral silyl enol ethers are found to be appropriate alkene components in stereoselective Paterno-Buchi reaction. The yields for the two diastereomeric oxetanes range from 44% to 76%. The substituent R in the y position needs to be bulky or polar to have a good facial diastereoselectivity. Three new stereogenic centers are formed via the photochemical transformation. Ring opening reactions have been applied to selected oxetanes.

A simple two-step procedure involving the condensation of a 1-alkynylcarbene complex with an enolizable carbonyl compound to afford a pyran-2-ylidene complex, which is subsequently reacted with an enamine to give the cyclohexadiene annulation product is used successfully for the syntheses of steroid-like ring skeletons. Bicyclic ring skeletons, steroid-like molecules and tetracyclic compounds are obtained mainly in good chemical yields and under mild conditions.

The piperidine ring is found in abundance in natural products. It is also widely seen in synthetic compounds with biological activity. As a result, a significant amount of attention has been focused on the stereoselective construction of piperidenes. Examples of such stereoselective construction include Eschenmoscher contraction and Lewis acid-induced cyclization of imines. A new method, one that allows the diastereoselective synthesis of 3-aminopiperidines, is presented.

The rigid C1-bridged dilithiobis(cyclopentadienide) exhibits a cyclotetrameric (Li2(Cp-R-Cp))4 supramolecular structure. The Li2 is eta(super 5)-coordinated to the exposed face of the tetrahydroindenyl substrate. The projection of the unit cells reveal that 4*tmeda tetramers form a columnar conformation in the crystal. The arrangement in the compound depends upon the nature of the ligand system. The study uses X-ray diffraction and quantum chemical calculations.

The planar tetracoordinate carbon center of the (mu-propynyl)(mu-sigma1:sigma2-MeCCMe)(Cp2Zr)2 (5b) cation complex is more stable by about 10-12 kcal/mol(super -1) compared to three coordinate sp2-hybridized carbon in the 5 complex's framework. The C(sub 2v)-symmetric intermediate structure probably is a transition state on the hypersurface of the thermally initiated automerization reaction of 5. The reaction between bis(propynyl)zirconocene and (Cp2ZrCH3(THF)(super +))(BPh4)(super -), involving memory effect generates 5. A molecular orbital analysis of 5 is discussed.

This article describes the synthesis and structure of heptamethylcycloheptatriene from hexamethylbenzene along with the former's cation species C(sub)7Me(sub)7 complexed with the transition metal ligand BF(sub)4.

A furan-derived sulfone reacts with 1 equivalent of sodium bis(2-methoxyethoxy)aluminum dihydride to form a bicyclic compound, substituted cyclohexanols. This reaction involves an elimination step and an alkoxide-influenced remote conjugate hydride addition. Organolithium reagents react with sulfone to give alkylated products that involve a tandem elimination/1,6 addition. The reaction proves the mechanism of the formation of the bicyclic compound.

Internal alkynes have undergone 1,1-carboboration reactions upon treatment with boranes RB[([C.sub.6][F.sub.5]).sub.2] (R = [C.sub.6][F.sub.5], C[H.sub.3]) to produce trisubstituted alkenylboranes. These products are used as substrates in Pd-catalyzed cross-coupling reactions.

The B[F.sub.3].O[Et.sub.2]-mediated allylation of isatin with an [alpha]-chiral allylic stannane is shown to be diastereo- and enantioselective. Absolute and relative configurations are secured by X-ray analysis of major isomers, the stereochemical assignment of the other 3-substituted 3-hydroxy oxindoles is based on similar NMR spectroscopic characteristics and the observations are rationalized by an acyclic transition state model.

High-level quantum chemical calculations are performed on the two epimeric pairs of complexes 4.2 and 6.2 obtained by lithiation of cinnamyl carbamate and 1-naphthyl derivative in the presence of BOX ligands (S,S)- and (R,R)-2. The studies have shown that in the case of configurationally labile complexes and a dynamic thermodynamic resolution one of both epimers is energetically favored and the quantum chemical computations have allowed the prediction of the enantiomeric excess

An unprecedented cascade of reactions is described after acid-catalyzed hydrolysis of tert-butyl (2S,5S)-2-tert-butyl-5-(2-fluoroallyl)-3-methyl-4-oxoimidazolidine-1-carboxylate that has led to pipecolic acid derivatives. The pipecolic acid is used for preparing (2R,4R,6S)-6-tert-butyl-4-hydroxypiperidine-2-carboxylic acid.

The intramolecular frustrated Lewis pair [(mesityl).sub.2]P-C[H.sub.2]-C[H.sub.2]B[([F.sub.6][F.sub.5]).sub.2] is generated in situ by HB[([C.sub.6][F.sub.5]).sub.2] hydroboration of dimesitylvinylphosphine and it has reacted with 1-pentyne by C-H bond cleavage. The studies have shown that the reaction has taken place in an asynchronous concerted fashion with the B-C bond being formed in slight preference to the P-C bond.

The preparation and structural characterization of an exceedingly sterically demanding, rigid, and chiral NHC ligand, IBiox[(-)-menthyl], is described. The ability to use aryl chloride substrates in intramolecular palladium-catalyzed [alpha]-arylations has disclosed its unique reactivity and [C.sub.2]-symmetric IBiox[(-)-menthyl] has allowed the highly enantioselective formation of oxindoles with up to 99% ee.

Trifluoromethyl-substituted 1-amino-1,4-dien-3-ones have undergone a cascade reaction involving inter alia two electrocyclizations upon treatment with a large excess of trifluoromethanesulfonic acid to give novel dihydrospiroindenepyrazole and dihydroindenodiazepine. X-ray diffraction is used for characterizing one 1-amino-1-penta-1,4-dien-3-one and several dihydrospiroindenepyrazoles and dihydroindenodiazepines.

Asymmetric synthesis of enantiomerically pure 2-substituted tetrahydro-3-benzazepines is described. The studies have shown that both [[sigma].sub.1] ligands are very selective against the [[sigma].sub.2] subtype and the PCP binding site of the NMDA receptor.

The bis(arylimino-Cp)Zr[Cl.sub.2] complex (I) has formed an 'antagonistic' Lewis pair with B[([C.sub.6][F.sub.5]).sub.3]. The treatment with dihydrogen has produced the aminomethyl-Cp hydrogenation product (II) by using quasi-autocatalytic process and the salt is an efficient catalyst for the hydrogenation of bulky imines and of silyl enolethers.

The synthesis and characterization of the five-membered organometallic zirconacycloallenoid products obtained from reaction between the bis-acetylide zirconocene complexes and HB[([C.sub.6][F.sub.5]).sub.2] is reported. The organometallic system with their highly strained distorted purely carbocyclic relatives represented a unique class of five-membered metallacyclic system.

The preparation, crystal structure and thermal and explosive characteristics of the phenylenediammonium diperchlorate (PDADP) salts are described. The studies have shown that the oxidation-reduction reactions near the surface of thermolysing perchlorates are responsible for the decomposition followed by explosion.

X-ray crystallography is used for the preparation and characterization of the perchlorate complexes of manganese, nickel and zinc with hexamethylenetetramine (HMTA). The perchlorate ion is attached to metal through water and the complexes have undergone thermal decomposition in two steps.

The study explains the design, characterization and the optical properties of several new Yb/Yb and Yb/Al helicates. The results show that these helicates can be easily used as extremely efficient near-infrared (IR) emitters.

The (lig)Co(I)CH3 complexes gave active ethene polymerization catalysts by treatment with Li[B(C6F5)(sub 4)]. The synthesis, some chemical and structural properties of Ziegler-Natta systems and their catalytic olefin polymerization properties upon activation with Li+ cation are described.

(F3C)F2SiONMe2 is a well suited model compound for an investigation of the nature of the bonding forces between Si and N atoms in germinal Si/N systems. (F3C)F2SiONMe2 shows a very strong Si...N interaction, which leads to a Si...N distance shorter than the Si-C bond in the same molecule.

A series of triplesalen ligands that bridge three salen coordination environments in a metaphenylene arrangement by a common phloroglucinol backbone is synthesized. The hexa-anionic forms are triple tetradentate ligands and are capable of coordinating three transition metal ions, as demonstrated by the synthesis of their trinuclear nickel complexes.

The ansa-zirconocene dichlorides [Me2Si(C5H4)(3-R-C5H3)]ZrCl2 (R=H, CH3, cyclohexyl, -CHMe2, -CMe3) were reacted with butadiene-magnesium to yield the respective (eta(super 4)-butadiene)-metallocenes. The subsequently formed series of [PMMA-C4H6-B(C6F5)(sub 3)](super -) anion oligomers was monitored and characterized by electrospray mass spectrometry.

Research has been conducted on N-acylamidines. The authors discuss the experimental and theoretical results concerning the complexation of substituted N-acylamidine ligands towars palladium(II), and the complexes' structures and their catalytic properties in Suzuki-Miyaura cross-coupling reactions.