Hydrosilylation of Olefins Activated on Highly Lewis-Acidic Calcium Cation.

The report introduces simple yet highly reactive calcium salt, Ca[Al(OR F ) 4 ] 2 (R F =C(CF 3 ) 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 SbF 5 . Reactivity tests show that it effectively catalyses the hydrosilylation of olefins with high regioselectivity, also in reactions involving sterically demanding substrates like (iPr) 3 SiH or tetrasubstituted olefins. Experimental and computational results point to the mechanism where the olefin molecule forms a complex with Ca 2+ , which significantly facilitates the attack of H-SiR 3 on the C=C double bond.