Stepwise Synthesis of Siloxane‐Substituted Oligoarsanes and Structural Investigation of Alkaline Earth Metal Derivatives

Abstract

The reaction between [Li(dme)AsH2] and (ClSiiPr2)2O gives a mixture of two products: the primary diarsanyldisiloxan (H2AsSiiPr2)2O (5) and the cyclic diarsanylsiloxane (HAsSiiPr2)2O (6). Through metallation of the mixture, the deprotonated species of both compounds could be obtained and isolated. Further reactions between the two metallated cyclic diarsanylsiloxanes (compounds 9 and 10) and (ClSiiPr2)2O both lead to the bicyclic compound As2[(iPr2Si)2O]2 (11). Subsequent oxidative coupling of 9 or 10 with C2H4Br2 as reagent leads to intermolecular As–As bond formation, yielding the quite remarkable compound As6[(iPr2Si)2O]3 (12), which features two siloxane‐bridged As3 rings. Compounds 5–12 were characterized by NMR, elemental analysis and X‐ray crystallography. Quantum chemical calculations were carried out to investigate the formation of the different products when arsenic (compound 12) is substituted by phosphorus (compound 4) in the final oxidation reaction of the cyclic compounds (HESiiPr2)2O. The calculations suggest a reaction path leading to 4 that is in agreement with experimental observations. The theoretical data also provide information that explains the experimental finding that two different products for E = P and E = As are formed under the same oxidative reaction conditions.

Synthesis of a Gallaarsene {HC[C(Me)N-2,6-i-Pr2-C6H3]2}GaAsCp* Containing a Ga═As Double Bond

“…The central structural motif in 3 is the bridging As 3 three-membered ring, which coordinates in η 1 ,η 2 fashion to two Ga atoms. Even though complexes containing cyclic P 3 and As 3 are known, the structural motif as observed in 3 has not been reported previously. Alternatively, the structure of 3 can be described as a LGaAs 3 butterfly-shaped structure, which is η 1 -coordinated by an additional L­(Cp*)Ga fragment.…”

Molecular Main Group Metal Hydrides

“…For example, Westerhausen showed that the calcium bis-amide Ca­[N­(SiMe 3 ) 2 ] 2 was able to deprotonate the silylated primary arsine H 2 As–Si i Pr 3 ( 1215 ) generating a new calcium bis­(silyl)­arsenide [Ca­(THF) 4 {AsH­(Si i Pr 3 )} 2 ] ( 1216 , eq 103 ). Related silylarsenides [As­(H)­SiR 3 ] − of strontium, barium, magnesium, zinc and lithium were also reported. − …”

Covalency and Ionicity Do Not Oppose Each Other—Relationship Between Si−O Bond Character and Basicity of Siloxanes

“…Therefore, much smaller Si‐O‐Si angles can be imposed in strained cyclic siloxane systems. As suggested by the angle–basicity correlation, their basicity will be substantially higher in comparison to the basicity of siloxane units incorporated into chains and consequently they have different material properties . Hence, the coordination chemistry of cyclic siloxanes has been the focus of much recent research …”