Hydrosilylation of Olefins Activated on Highly Lewis‐Acidic Calcium Cation

The report introduces simple yet highly reactive calcium salt, Ca[Al(ORF)4]2 (RF=C(CF3)3), 1, which effectively catalyses olefin hydrosilylation through an unusual mechanism involving the activation of the alkene molecule. Upon dissolution in o‐difluorobenzene (oDFB), 1 forms a highly Lewis acidic [Ca(oDFB)6]2+ complex. Our DFT calculations reveal that fluoride ion affinity is comparable to SbF5. Reactivity tests show that it effectively catalyses the hydrosilylation of olefins with high regioselectivity, also in reactions involving sterically demanding substrates like (iPr)3SiH or tetrasubstituted olefins. Experimental and computational results point to the mechanism where the olefin molecule forms a complex with Ca2+, which significantly facilitates the attack of H‐SiR3 on the C=C double bond. Readily available salt of Ca2+ with weakly coordinating anion [Al(ORF)4]− (RF=C(CF3)3) exhibits high Lewis acidity comparable to SbF5. Reactivity studies show it is an effective catalyst for olefin hydrosilylation, yielding anti‐Markovnikov regioisomer. Experimental and DFT studies indicate a unique mechanism for this type of reaction, which involves the activation of the olefin molecule by coordination with Ca2+.