[(η5‐CpR)Ge:]+[BArF4]−/O2 – A Sustainable and Efficient Catalytic System for the Hydrosilylation of Selected Olefins

Main group catalysis with germanium. Only 0.01 mol % of [(η ⁵-Cp^R)Ge:]⁺[BAr^F ₄]⁻ are necessary for the anti-Markovnikov hydrosilylation of alkenes in the presence of oxygen. O₂ directly activates the germanium borate complex which is quantified by kinetic measurements. The novel catalytic system is a transition metal-free, efficient, sustainable and air-stable catalyst alternative for the established noble metal complexes.

Abstract

The cationic Ge(II) borates [(η ⁵-Cp^R)Ge:]⁺[BAr^F ₄]⁻ (Cp^R=substituted cyclopentadienyl) efficiently catalyze the anti-Markovnikov hydrosilylation of alkenes in the presence of oxygen which is investigated using the examples of α-methylstyrene and 1-hexene. Full conversion is achieved with a minimal amount of 0.01 mol % of the cationic Ge(II) borate even at rt. The effect of oxygen is investigated and quantified by kinetic measurements which demonstrate that oxygen is an activator which interacts directly with the germanium complex. Solvent-free hydrosilylation conditions are realized by the introduction of a more lipophilic silylated borate counteranion. Thus, the novel catalytic system is an efficient, sustainable and air-stable catalyst alternative for the established hydrosilylation catalysts based on noble metal complexes.

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