Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

One-dimensional coordination polymers: applications to material science

N-silylated benzamidines: versatile building blocks in main group and coordination chemistry

Textbooks of inorganic chemistry describe the formation of adducts by coordination of an electron donor to an electron acceptor, often using the amine-boranes, X3N → BY3, as examples. In the Lewis (electron dot) formulas of the compounds, the dative bond in H3N → BH3 and the covalent bond in H3CCH3 are both represented by a shared electron pair. In the simple molecular orbital or valence bond models the wave functions of both electron pairs would be constructed in the same manner from the appropriate sp3 type atomic orbitals on the bonded atoms; the difference between the covalent and the dative bond becomes apparent only after the orbital coefficients have been analyzed. This may be the reason why many structural chemists seem reluctant to distinguish between the two types of bonds. The object of this article is to remind the reader that the physiocochemical properties of covalent and dative bonds may be – and often are – quite different, and to show that a distinction between the two provides a basis for understanding the structures of a wide range of main group metal compounds.

Covalent versus Dative Bonds to Main Group Metals, a Useful Distinction

Trans-effects in octahedral transition metal complexes

Barium hexamethyldisilazide tetrahydrofuranate, Ba(N(SiMe{sub 3}){sub 2}){sub 2}(THF){sub 2} (1), is synthesized from barium granules and 1,1,1,3,3,3-hexamethyldisiliazane at 25{degree}C in THF. Gaseous ammonia is a necessary catalyst. In the solid state, the compound is a monomer containing a tetrahedral four-coordinate barium center. One of the coordinated THF molecules is removed from 1 by stripping a toluene solution of 1 to dryness in vacuo, yielding (Ba(N(SiMe{sub 3}){sub 2}){sub 2}(THF)){sub 2} (2). In the solid state, 2 is a dimer containing two bridging and two terminal hexamethyldisilamido groups. The four-coordinate, tetrahedral geometry at each barium is completed by terminal THF molecules. The solvent-free compound (Ba(N(SiMe{sub 3}){sub 2}){sub 2}){sub 2} (3) is obtained by sublimation of 1. This compound is a dimer in the solid state, with three-coordinate barium centers. Crystal data are reported for all these compounds 14 refs., 3 figs., 9 tabs.

Syntheses and structures of a series of very low coordinate barium compounds: Ba[N(SiMe3)2]2(THF)2, {Ba[N(SiMe3)2)]2(THF)}2, and {Ba[N(SiMe3)2]2}2

Le complexe (t-BuO) 3 W≡CMe cristallise dans le groupe P1 et le complexe (t-BuO) 3 W≡N dans le groupe P6 3 cm. Coordination bipyromidale rhomboedrique autour des atomes de tungstene. Le compose ethylidyne a une structure centrosymetrique mettant en jeu deux unites bipyramidale rhomboedrique possedant une arete commune. Le compose nitruro est lineaire et polymere

Isoelectronic molecules with triple bonds to metal atoms (M = Mo, W): crystal and molecular structures of tri-tert-butoxytungsten ethylidyne and nitride

Identification of the zinc reduction product of vcl3.3thf as [v2cl3(thf)6]2[zn2cl6]

Chloro(dimethylamido) compounds of tantalum(V): Preparations, properties, and structures of [Ta(NMe2)3Cl2]2, TaCl3(NMe2)2(HNMe2), Ta(NMe2)3Cl2(HNMe2), and [TaCl2(NMe2)2(HNMe2)]2O

Aus aquimolaren Mischungen von Hexamethylbenzol (I) und dem Salz (II) in-Trifluoressigsaure last sich unter kontrollierten Bedingungen ein 1:1-Elektronendonator-Akzeptor-Komplex (III) in kristalliner Form isolieren.

John C. Huffman

Papers

Syntheses and structures of a series of very low coordinate barium compounds: Ba[N(SiMe3)2]2(THF)2, {Ba[N(SiMe3)2)]2(THF)}2, and {Ba[N(SiMe3)2]2}2

Isoelectronic molecules with triple bonds to metal atoms (M = Mo, W): crystal and molecular structures of tri-tert-butoxytungsten ethylidyne and nitride

Identification of the zinc reduction product of vcl3.3thf as [v2cl3(thf)6]2[zn2cl6]

Chloro(dimethylamido) compounds of tantalum(V): Preparations, properties, and structures of [Ta(NMe2)3Cl2]2, TaCl3(NMe2)2(HNMe2), Ta(NMe2)3Cl2(HNMe2), and [TaCl2(NMe2)2(HNMe2)]2O

Molecular structure and charge transfer excitation of electron donor-acceptor complexes. Ion pairs from arenes and mercury(II)