Formation and Reactivity of a Hexahydridosilicate [SiH6]2− Coordinated by a Macrocycle‐Supported Strontium Cation.

The cationic benzyl complex [(Me4TACD)Sr(CH2Ph)][A] (Me4TACD=1,4,7,10‐tetramethyltetraazacyclododecane; A=B(C6H3‐3,5‐Me2)4) reacted with two equivalents of phenylsilane to give the bridging hexahydridosilicate complex [(Me4TACD)2Sr2(thf)4(μ‐κ3 : κ3‐SiH6)][A]2 (3 a). Rapid phenyl exchange between phenylsilane molecules is assumed to generate monosilane SiH4 that is trapped by two strontium hydride cations [(Me4TACD)SrH(thf)x]+. Complex 3 a decomposed in THF at room temperature to give the terminal silanide complex [(Me4TACD)Sr(SiH3)(thf)2][A], with release of H2. Upon reaction with a weak Brønsted acid, CO2, and 1,3,5,7‐cyclooctatetraene SiH4 was released. The reaction of a 1 : 2 mixture of cationic benzyl and neutral dibenzyl complex with phenylsilane gave the trinuclear silanide complex [(Me4TACD)3Sr3(μ2‐H)3(μ3‐SiH3)2][A], while nOctSiH3 led to the trinuclear (n‐octyl)pentahydridosilicate complex [(Me4TACD)3Sr3(μ2‐H)3(μ3‐SiH5nOct)][A]. [ABSTRACT FROM AUTHOR]