Reactions of Metal Anions with Halosilanes

Carbonylate anions are the most suitable starting material for the synthesis of silylmetal compounds. A prerequisite for the preparation of compounds with a formal M = Si double bond is the use of metallate dianions like Na2Fe(CO)4 (Collman s reagent) together with the respective dichlorosilanes [96]. 

Investigations of carbonylate polyanions have been intensely pursued by Ellis and co-workers [97-107], 

Most of the compounds have been found to react as supemucleophiles. 

The chlorosilanes are available from classical synthetic routes [108]. In most cases the products can be obtained from SiCl4 and the lithium salts of the introduced substituents with sufficient selectivity and in high yield. This is particularly true for the alcoholates and the thiolates. The exchange problems R vs. Cl which arise with the t-butylthiochlorosilanes will not be discussed in detail here. These problems are overcome by an appropriate choice of the reaction conditions. 

It is known that Na2Fe(CO)4 can be silylated twice to form cri-[(H3C)3Si]2Fe(CO)4 [109]. Also the reaction of Na2Fe(CO)4 with 1.1-dichlorosilanes has been described and leads exclusively to the dimeric compounds [110, 111], In polar solvents the formation of dimers can be suppressed and monomeric base-stabilized compounds are obtained. A very elegant procedure is the in-situ generation of the carbonylate anions in solution by deprotonation of H2Fe(CO)4. 

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