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Związki alkoholanowe w syntezie nanomateriałów

John Ł., Sobota P.

Wiadomości Chemiczne

2011

[Z] 65, 9-10

839-868

Polynuclear metal alkoxides are nearly as common in today’s chemistry as any other simple inorganic complexes and constitute an interesting family of species with a very broad structural diversity (Fig. 3 and Tab. 1) [14]. These compounds form structural motifs which range from simple bimetallic complexes to very specific aggregates that result from the versatile coordinating abilities of an alkoxo and aryloxo ligands (Fig. 1). For the last few decades, there has been a growing interest in the development of the chemistry of metal alkoxides. Such interest derives from their fascinating structural chemistry, interesting catalytic properties, and a high potential for industrial utilization. The fact that most of them can generate highly pure and well-defined metal oxides (Table 4) has resulted in high research activity in chemistry of materials. Alkoxides and their derivatives, e.g. organometallics, are easily accessible and consist inexpensive compounds. Moreover, alkoxide ligands are easily removable during thermal treatment in a relatively low temperatures compare to conventional methods involving inorganic salts. Such compounds already have metal-oxygen bonds established on molecular structure. Due to these, alkoxides can generate oxide ceramics in a single step – so-called single-source precursors (SSPs) [11]. SSPs deliver appropriate metal elements of a final oxide product(s) eliminating the need to match the reaction rates required from a multicomponent mixture. All of these features made the metal oxides derived from metal alkoxides highly pure products possessing specific properties, chemical and mechanical resistance, excellent functions and shapes. The aim of this article is to serve as a guide in understanding the principles in a one step strategy for oxide ceramics using metal alkoxide compounds. It includes synthesis of alkoxides and their derivatives, the concept of SSPs strategy and design of molecular precursors for oxide ceramic materials.

Kompleksy metali z ligandami boryloksylowymi

Luliński S., Serwatowski J.

Wiadomości Chemiczne

2006

[Z] 60, 7-8

467-486

The review deals with metal complexes bearing various types of boroxide ligands. It is divided into several chapters including synthesis, structural and spectroscopic (NMR) characterization followed by reactivity and catalytic properties of some novel compounds. Metal complexes with boroxide ligands can generally be defined as derivatives of hydroxydiorganoboranes R2BOH or dihydroxyorganoboranes RB(OH)2, where one or two hydrogen atoms are replaced with a metal. A few complexes with a closely related R,B2Oj ligand derived from triorganoboroxin [RBO]3 have also been included. Boroxide ligands may be regarded as electron defficient analogues of alkoxide ligands, due to specific electronic properties of a trivalent boron atom, which is able to interact by means of its 2p orbital with a lone electron pair of an adjacent oxygen atom. As a result of this so-called back-bonding, the B-O bond order is increased, whereas the ^-donor properties of oxygen are reduced. Accordingly, a metal oxygen bond is weakened. Another important point is that boroxides are sterically less crowding than bulky aryloxide ligands having comparable electronic properties. Hence, an increased reactivity of such complexes is expected, especially as catalysts or initiators in various polymerization processes.