Donald C. Bradley

Bio: Donald C. Bradley is an academic researcher from University of London. The author has contributed to research in topics: Mercury probe & Metalorganic vapour phase epitaxy. The author has an hindex of 2, co-authored 3 publications receiving 98 citations.

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

Abstract: 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.

Group 13 compounds incorporating Salen ligands.

Abstract: In a previous review it was predicted that "the reactivity of five-coordinate complexes would certainly be different than that of the four-coordinate derivatives". Structurally and spectroscopically, there is very little difference in the higher-coordinate compounds when compared to the four-coordinate derivatives. However, the prediction was remarkably accurate, if not a bit understated, for the reactivity of these compounds. There appears to be a tremendous potential in catalysis and synthesis for the five-coordinate derivatives, far more possibilities than exist for the lower-coordinate derivatives. Furthermore, the higher-coordinate derivatives are rarely air or moisture sensitive and, thus, may be handled under a wider range of conditions. Although reactions such as oxirane and lactide polymerizations are fairly well-known now with five- and six-coordinate aluminum compounds, the potential of these compounds has only begun to be developed. It is easy to imagine that these types of compounds will see wider use than the related transition-metal compounds.

Kovalente und dative Bindungen zu Hauptgruppenmetallen, eine nützliche Unterscheidung

Abstract: Lehrbucher der Anorganischen Chemie beschreiben die Bildung von Addukten als Koordination eines Elektronendonors an einen Elektronenacceptor, wobei als Beispiele oft die Amin-Borane X3N → BY3 herangezogen werden. In den Lewis(Elektronenstrich)-Formeln werden sowohl die dative Bindung (z. B. in H3N → BH3) als auch die kovalente Bindung (z. B. in H3CCH3) durch ein gemeinsames Elektronenpaar wiedergegeben. In den einfachen Molekulorbital- und Valence-Bond-Modellen wird in beiden Fallen die Wellenfunktion dieses Elektronenpaars auf die gleiche Weise aus geeigneten sp3-hybridisierten Atomorbitalen der beteiligten Atome konstruiert. Der Unterschied zwischen kovalenter und dativer Bindung tritt erst in Erscheinung, wenn die Orbitalkoeffizienten genau analysiert werden. Dies mag der Grund sein, weshalb so viele Strukturchemiker nur sehr widerwillig zwischen diesen beiden Bindungstypen unterscheiden wollen. Ziel dieses Aufsatzes ist es, dem Leser in Erinnerung zu rufen, das sich die physikochemischen Eigenschaften kovalenter und dativer Bindungen deutlich unterscheiden konnen – und sich oft auch tatsachlich unterscheiden-, und zu zeigen, das diese Betrachtungsweise eine gute Basis fur das Verstandnis der Strukturen einer Fulle von Hauptgruppenmetallverbindungen ist.