Angewandte Chemie International Edition in English

The cover pictur shows the ball-and-stick model of a [{RhBi ₇}Br ₈] cluster from the structure of one of the first ternary subhalides of bismuth, Bi₇ RhBr₈. The seven bismuth atoms(blue) surround the central rhodium atom (yellow) forming a regular pentagonal bipyramid. The two apical bismuth atoms are each in an approximate square-planer environment of four bromine atoms. The squares are staggered and thus the {RhBi₇} bipyramid is surrounded by a distorted square antiprism of bromine atoms. On closer analysis, this apparently unfavorable atomic arrangement emerges as an exceptional solution to the need to satisfy the electronic requirements of all participating atoms. More about this as yet unique molecular cluster is discussed by M. Ruck on pages 1971 ff. The graphics were generated by M. Ruck and G. Baum with the program POV-Ray.

“Being isolated in those pre-fax and pre-e-mail days in Australia was a great advantage, as it allowed time to discuss and to think things through. We had outspoken and informed local critics, the freedom and resources to pursue our own ideas, and were given full credit for our efforts. Those of us who have senior roles in science need to do everything possible to ensure that comparable opportunities and environments remain available to young scientists.” With this provocative exhortation P.C. Doherty ended his Nobel Lecture.

In the complex balance between virus and host the T cells and the properties of the virus play an important role. The unexpected discovery of the MHC-restricted T cell recognition (MHC = major histocompatibility complex) prompted many important investigations. Which have led to a detailed understanding on a molecular level of T cell recognition of virus-infected target cells. As a result of these findings the immunological specificity as well as the immunological memory, and above all, pathogenesis of infectionus diseases and of autoimmunity can be better understood.

The allure of cascade molecules has long since reached main group chemistry. Dendrimers constructed from silicon- and phosphorus-based building blocks (see schematic representation on the right) not only are among the largest cascade molecules ever synthesized, but also offer unique possibilities for binding functional groups at the surface or in the interior. This property may open new perspectives for the design of catalysts and synthetic reagents.

Great advances have been made in the treatment of Tay–Sachs disease, one of a group of inherited diseases in which the degradation of sphingolipids is impaired. In the animal model, application of compound 1 was successful in inhibiting the biosynthesis of nondegradable enzyme substrates and in this way reducing the extent of the disease.

Functions similar to those of catalytic antibodies are shown by molecularly imprinted polymers, when the cavities in the polymer not only have the correct form but also contain catalytically active groups. Polymers have now been prepared by imprinting with a transition state analogue of alkaline ester hydrolysis (see picture). These “artificial enzymes” combine strong catalytic activity with typical enzyme properties such as Michaelis—Menten kinetics, competitive inhibition, turnover, and substrate selectivity.

Only corner-sharing between the seven TaO₆ octahedra is observed in the neutral complex [H₋₁₁Ta₇O₁₂(tdci)₆] (tdci = 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol). The structure on the right (only one tdci ligand is illustrated) depicts the Ta₇O₃₀ double adamantane core. In contrast to previously described structures of polyoxometalate ions, which have a predominantly edge-shared framework, this compound has an unusually open structure.

Avoidance of a metal–metal bond is a significant factor favoring the formation of the nonanuclear cobalt complex [CO₉(chp)₁₈] (framework depicted on the right; chp = 6-chloro-2-pyridonate). The complex is homoleptic, which is unusual for 3d-complexes of pyridonates, and this contrasts with the similar, but heteroleptic, nickel double adamantane frameworks also reported.

Merely the illusion of a GaGa bond is given between the doubly I-bridged atoms of the nearly planar eight-membered ring in Ga₈I₈ · 6 PEt₃ (shown on the right). This finding is remarkable, since the corresponding Al^I halides have four-membered Al rings. D = PEt₃.

A unique type of cluster, the [{RhBi₇}Br₈] molecules, is the building block from which the halogen-rich bismuth subbromide Bi₇RhBr₈ is constructed. The Bi atoms are arranged as a pentagonal bipyramid around the central Rh atom, and they, in turn, are surrounded by the Br atoms as a square antiprism (shown on the right; Rh = dark gray, Bi = black, Br = pale gray). In contrast to Bi₇RhBr₈, the metalrich bismuth subiodides known to date are not composed of discrete molecules.

Condensed double chains of edge-sharing scandium octahedra are contained in Sc₂Te. These structural units are augmented by more loosely bound pyramidal and zigzag scandium aggregates. On the right is a projection of these chains together with tellurium (the open circles). The metal array may be viewed as the result of the dissociation of the metal framework in electron-richer chalcogenides.

Glycopeptide libraries in which both the carbohydrate part and the peptide part have been varied can be generated by stereoselctive glycosylation of free hydroxy groups of support-bound peptides with glycosyl trichloroacetimidates. The use of temporary t Bu protecting groups enabled the stereoselctive synthesis of a model library of four glycopeptides (one is depicted on the right) that each have two different glycosyl groups.

A significantly larger variety of ligand combinations is possible for rectangular [m × n] grids (such as the first complex of this type, [2 × 3] grid 1) than for symmetric square [n × n] grids. The product distribution [2 × 3]:[2 × 2]:[3 × 3] for the reaction of tri- and ditopic ligands with Ag^I ions in a 2:3:6 ration is 90:8:2! The spheres represent the Ag^I ions.

Photolytic cleavage of TePh₂ from the phosphane- stabilized, hexanuclear cluster 1 results in the mixed telluride–tellurolate cluster 2 in good yields (the structure of the anion in 2 is shown on the right; dark spheres represent Te atoms, hashed spheres Cu atoms, and white spheres P atoms.

An alkyne–vinylidene isomerization is also possible with the difluoro compounds 1 and 2! Irradiation of 2 (λ = 193 nm) in an Ar matrix yields 1 exclusively. The IR spectrum agrees with results of novel abinitio calculations, which also suggest that 1—in sharp contrast to the vinylidenes RHCC—is protected against isomerization into 2 by a kinetic barrier. Irradiation with light with λ > 230nm converts 1 back into 2. Already at 35–42 K 1 adds CO and N₂ to yields F₂CCCO and F₂CCNN, respectively.

Depending on the type of substituent on the nitrogen atom, the two thirtysix atom clusters of main group elements formed on treating RNSO with LiNHtBu adopt different structures (R = t Bu, SiMe₃). For instance, the compound depicted on the right can be described as an aggregate of three hexagonal prisms.

Double regioselective glycosylation is the key to the generally applicable strategy by which two triantennary octasaccharides and the tetraantennary nanasaccharide 1 are available. A modular system of oligosaccharides building blocks is the basis of an efficient synthesis of complex N-glycans with the desired number of branches in unexpectedly high yields.

Starting from a diphosphazene as a molecular precursor, single-phase HP₄N₇ could be synthesized for the first time. The structure was determined from power-diffraction investigation with synchrotron radiation. A section of the crystal structure is shown on the right.

Depending on the donor strength of the base, tri-, di-, or mononuclear complexes are formed on reaction of the tetranuclear complex [{Me₃Pt(O₃SCF₃)}₄] (structure depicted on the right) with Lewis bases. These complexes of different nuclearity offer a rich synthetic potential because of their precisely tunable properties.

The exceptionally long (4.5 nm) monodisperse polycyclic aromatic hydrocarbon 1 contains 29 condensed five-and six-membered rings. Since the dodecyl chains make this extended, flat (tabular) molecule unusually soluble in common organic solvents, it can be readily characterized. Compound 1 can be reduced to the octaanion within a relatively small potential range, and the tetraction that forms on oxidation is stable for several seconds.

A target antigen for cancer immunotherapy, ganglioside GM2, is expressed on the cell surface of several human cancer types. An efficient chemical synthesis can now make available ample amounts of a structurally well-defined synthetic GM2, free of biological contaminants. This greatly facilitates the systematic construction of safe and efficient GM2 cancer vaccines.

Extreme sensitivity to change in the lattice is observed for electron-transfer rates in the Fe^II/Fe^III title compound, as shown by Mössbauer spectroscopic investigations of the two crystallographic phases in which the compound can be isolated. The structure of the cation and anion in the monoclinic phase P2₁/n is shown on the right.

A nonplanar arrangement of four ligands is intrinsic to the title compound is solution and in the crystal. There is no interaction between the Ru center and the Counterion [3,5-(CF₃)₂ C₆H₃]₄B⁻. Density functional theory calculations of the model complex [Ru(Ph)(CO)(PH₃)₂]⁺ provided the structure shown on the right, which shows no ortho-CH … Ru interaction.

The structure of the exciting blue form of a new hexaaminecobalt(III) cage compound (Lewis structure shown on the right) was not known, while that of the more usual yellow conformer was determined experimentally. A combination of molecular-mechanics calculations and the simulation of spectroscopic and electrochemical properties can be used to determine the structure, and to interpret the unprecedentedly low ligand field and high redox potential.

A variant of the BaAl₄ structure, the α-La₃Al₁₁ structural type is observed upon crystallization of the new ternary intermetallic phase Ln₃Au₂Al₉ (Ln = Dy and Tb). Calculations of the electronic structure were used to investigate the characteristics of Au and Al atoms within the framework. The gray atoms in the picture of the structure prefer heteronuclear AuAl contacts over homonuclear AlAl and AuAu contacts.

Not 15, but 16 sulfur atoms are found in [NH₄]₃[Ir(S₄)(S₆)₂], which was first reported as “[NH₄]₃[IrS₁₅]” in 1904. This was determined by comparing the results of the crystal structure analysis (structure shown on the right) with the optical goniometric data reported in the original work. [NH₄]₃[Ir(S₄)(S₆)₂] spontaneously resolves upon crystallization. Therefore, these enantiomeric crystals were available a decade before Werner first separated optically active inorganic complexes.

NADH instead of hydroged peroxide is required by two newly identified, substrate-specific and regioselective halogenases. Both were isolated from a pyrrolnitrin-producing Pseudomonas fluorescens strain. One enzyme catalyzes the chlorination of L-tryptophan to 7-chloro-L-tryptophan (1).

The folding of the boratanaphthalene ring over the metal in 2 ensures that all ten non-hydrogen atoms are with in bonding distance to Zr. This complex with the novel boratanaphthalene ligand was furnished in an unprecedented ring annulations reaction of ethyne with the boratabenzene ligand 1.