Functional Organotin Alkynides as Precursors of Tin-Based Hybrid Materials
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Functional Organotin Alkynides as Precursors of Tin-Based Hybrid Materials Pascale Jaumier1, Bernard Jousseaume1, Hocine Riague1, Thierry Toupance1 and Mohamed Lahcini2 1 Université Bordeaux I, Laboratoire de Chimie Organique et Organométallique, UMR 5802, 33405, Talence, France, 2 Université Cadi Ayyad, Département de Chimie, Marrakech, Morocco. ABSTRACT Functional trialkynylorganotins were obtained by alkynylation of the corresponding organotin trichlorides. When functional organotin trichlorides were not stable, a selective monoalkynylation of tetraalkynyltins by Grignard reagents was used. It was the first example of selective monoalkylation reactions of symmetrically tetrasubstituted tin compounds. Then, reactions of the functional trialkynylorganotins with alcohols, water and carboxylic acids afforded respectively the corresponding functional monoorganotin alkoxides and oxides, and monoorganooxotins carboxylates. INTRODUCTION Organotin oxides, alkoxides and oxocarboxylates show important applications in organic synthesis and in industry as catalysts [1, 2]. They can be obtained from several routes mainly based on organotin trichlorides as reactants or intermediates [3]. Organotin oxides were first prepared by hydrolysis of organotin trichlorides, with unstable hydroxyde intermediates which dehydrate very rapidly. Hydrolysis of moisture-sensitive alkoxides and stannylamines constitutes a milder access to organotin oxides which allowed the isolation of clusters with twelve tin atoms and fourteen oxygen atoms at the early stage of the reaction [4]. RSnCl3
NaOH
RSn(OR')3
RSnO3/2 H2O
H2O
RSn(NR'2)3
[(RSn)12(µ3-O14(µ-OH)6](OH)2
The usual entry to tin alkoxides consists of a reaction between organotin chlorides and metal alkoxides. They can also be obtained in milder conditions under treatment of organotin trichlorides with alcohols in the presence of two equivalents of diethylamine [5]. Cleavage of tinnitrogen bonds with alcohols also allows the preparation of organotin trialkoxides, which is advantageous when a volatile amine is formed [6]. RSnCl3
NaOR' or R'OH, Et2NH
RSn(OR')3
CC1.2.1
R'OH
RSn[N(C2H5)2]3
Organooxotin carboxylates, which can be either tri-, tetra- or hexameric, are usually obtained by treatment of an oxide with an organic acid under Dean-Stark conditions to displace the water formed [7]. R1SnO3/2
R2CO2H - H2O
[R1Sn(O)O2CR2]6
On the other hand, organic phases incorporated in materials obtained by the sol-gel process improve their mechanical properties, especially when covalent bonding exists between both phases, as in organic-inorganic composites. Most examples of these materials only concern silicon derivatives, since with transition metals the more ionic metal-carbon bonds are not stable enough towards hydrolysis [8]. Tin shows a behaviour intermediate between those of silicon and transition metals. The tin-carbon bonds are strong and resistant to hydrolytic conditions, whereas tin-alkoxyl bonds are weak and easily cleaved under reaction with water. Tin is thus a good candidate for
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