New Self-Assembled Structural Motifs in Coordination Chemistry.

The Cambridge Crystallographic Data Centre (CCDC) was established in 1965 to record numerical, chemical and bibliographic data relating to published organic and metal–organic crystal structures. The Cambridge Structural Database (CSD) now stores data for nearly 700 000 structures and is a comprehensive and fully retrospective historical archive of small-molecule crystallography. Nearly 40 000 new structures are added each year. As X-ray crystallography celebrates its centenary as a subject, and the CCDC approaches its own 50th year, this article traces the origins of the CCDC as a publicly funded organization and its onward development into a self-financing charitable institution. Principally, however, we describe the growth of the CSD and its extensive associated software system, and summarize its impact and value as a basis for research in structural chemistry, materials science and the life sciences, including drug discovery and drug development. Finally, the article considers the CCDC’s funding model in relation to open access and open data paradigms.

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The Cambridge Structural Database in retrospect and prospect.

The chemistry of lithium enolates is used to demonstrate that complex structures held together by noncovalent bonds (“supramolecules”) may dramatically influence the result of seemingly simple standard reactions of organic synthesis. Detailed structural data have been obtained by crystallographic investigations of numerous Li enolates and analogous derivatives. The most remarkable features of these structures are aggregation to give dimers, tetramers, and higher oligomers, complexation of the metal centers by solvent molecules and chelating ligands, and hydrogen-bond formation of weak acids such as secondary amines with the anionoid part of the enolates. The presence in nonpolar solvents of the same supramolecules has been established by NMR-spectroscopic, by osmometric, and by calorimetric measurements. The structures and the order of magnitude of the interactions have also been reproduced by ab-initio calculations. Most importantly, supramolecules may be product-forming species in synthetic reactions of Li enolates. A knowledge of the complex structures of Li enolates also improves our understanding of their reactivity. Thus, simple procedures have been developed to avoid complications caused by secondary amines, formed concomitantly with Li enolates by the common methods. Mixtures of achiral Li enolates and chiral Li amides can give rise to enantioselective reactions. Solubilization by LiX is observed, especially of multiply lithiated compounds. This effect is exploited for alkylations of N-methylglycine (sarcosine) CH2 groups in open-chain oligopeptides. Thus, the cyclic undecapeptide cyclosporine, a potent immunosuppressant, is converted into a THF-soluble hexalithio derivative (without epimerization of stereogenic centers) and alkylated by a variety of electrophiles in the presence of either excess lithiumdiisopropyl amide or of up to 30 equivalents of lithium chloride. Depending on the nature of the LiX additive, a new stereogenic center of (R) or (S) configuration is created in the peptide chain by this process. A structure-activity correlation in the series of cyclosporine derivatives thus available is discussed.

Structure and Reactivity of Lithium Enolates. From Pinacolone to Selective C‐Alkylations of Peptides. Difficulties and Opportunities Afforded by Complex Structures

Anionic polymerization is a powerful tool for the synthesis of a variety of model materials with well-defined molecular characteristics. However specially designed apparatuses and appropriate high vacuum techniques are needed in order to exclude from the reaction environment all reactive contaminants with the anionic centers. This review describes the basic principles of anionic polymerization as well as detailed experimental methods for the purification of the reagents usually used for the synthesis of model polymeric materials. In addition a few examples of the synthesis of polymers with complex architecture are given. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3211–3234, 2000

https://onlinelibrary.wiley.com/doi/pdf/10.1002/1099-0518%2820000915%2938%3A18%3C3211%3A%3AAID-POLA10%3E3.0.CO%3B2-L

Anionic polymerization: High vacuum techniques

Publisher Summary This chapter discusses the current patterns and perspectives in organolithium chemistry, including the structures of organonitrogenlithium (N-Li) compounds. The chapter explains the compounds with N-Li bonds. These are chiefly lithium imides [iminolithiums (RR’C=NLi) n ] and their complexes with added Lewis bases (L), and lithium amides [amidolithiums (RR’NLi) n ] and their complexes. For the lithium amide species, particularly, only those whose R,R’ groups that do not contain additional functionalities are described—that is, the R,R’ groups remain largely uninvolved with lithium centers. These species are termed “simple” lithium amides. N-Li compounds and, particularly, lithium amides (R 2 NLi) are widely used both in organic and in organometallic syntheses. For the former, these strong bases are employed as proton abstractors to generate new organolithiums. Although synthetic uses have dominated the interest in N-Li compounds, the chapter focuses on the structures. Most of the physical properties of organolithium compounds (the marked exception being conductance) arise, because of the overall size and shape of the units making up these materials and the nature of the peripheries of these units. The basic structural building block of any organolithium is an ion pair, R – L + . The identities and structures of complexed organolithiums are of particular importance.

Structures of Organonitrogen—Lithium Compounds: Recent Patterns and Perspectives in Organolithium Chemistry

Tables of Interatomic Distances and Configuration in Molecules and Ions, herausgeg. von A. D. Mitchell und L. C. Cross. Special Publication No. 11. Wiss. Herausgeber: L. E. Sutton. The Chemical Society, London 1958. 1. Aufl., 385 S., geb. £ 2.2.0

Low temperature study of the structure of crystalline ethyllithium

Über metallalkyl- und aryl-verbindungen ☆: XXXV. Zur struktur von allyllithium. Darstellung und kristallstruktur einer monomeren allyllithium-verbindung, allyl(pentamethyldiethylentriamin)lithium, LiC3H5(Me2NC2H4N(Me)C2H4NMe2)

Die Röntgenstruktur von N-Lithiocarbazol-Dimer: Experimentelle Bestätigung der theoretischen Analyse von Strukturen des N-Lithiopyrrol-Typs

Unlike organolithium compounds,’ relatively few structures of the synthetically important organic derivatives of the heavier alkali metals have been reported.2 A new hexane-soluble butylsodium reagent’ facilitates the preparation of crystalline organosodium compounds.3b Thus, metalation of toluene in hexane at -18 OC in the presence of N,N,N’,N’-tetramethylethylenediamine (TMEDA) gave yellow needles of (NaCHzC,H,-TMEDA),.4a

Pentacoordinate carbon in trigonal-bipyramidal symmetry. The eight-membered x-ray structure of tetrakis(benzylsodium-N,N,N',N'-tetramethylethylenediamine).

Hans Dietrich

Papers

Tables of Interatomic Distances and Configuration in Molecules and Ions, herausgeg. von A. D. Mitchell und L. C. Cross. Special Publication No. 11. Wiss. Herausgeber: L. E. Sutton. The Chemical Society, London 1958. 1. Aufl., 385 S., geb. £ 2.2.0

Low temperature study of the structure of crystalline ethyllithium

Über metallalkyl- und aryl-verbindungen ☆: XXXV. Zur struktur von allyllithium. Darstellung und kristallstruktur einer monomeren allyllithium-verbindung, allyl(pentamethyldiethylentriamin)lithium, LiC3H5(Me2NC2H4N(Me)C2H4NMe2)

Die Röntgenstruktur von N-Lithiocarbazol-Dimer: Experimentelle Bestätigung der theoretischen Analyse von Strukturen des N-Lithiopyrrol-Typs

Pentacoordinate carbon in trigonal-bipyramidal symmetry. The eight-membered x-ray structure of tetrakis(benzylsodium-N,N,N',N'-tetramethylethylenediamine).