Electrophilic Si−H Activation by Acetonitrilo Benzo[h]quinoline Iridacycles: Influence of Electronic Effects in Catalysis

Abstract The performance of six newly synthesized benzo[ h ]quinoline‐derived acetonitrilo pentamethylcyclopentadienyl iridium(III) tetrakis(3,5‐bis‐trifluoromethylphenyl)borate salts bearing different substituents −X (−OMe, −H, −Cl, −Br, −NO 2 and −(NO 2 ) 2 ) on the heterochelating ligand were evaluated in the dehydro‐ O ‐silylation of benzyl alcohol and the monohydrosilylation of 4‐methoxybenzonitrile by Et 3 SiH, two reactions involving the electrophilic activation of the Si−H bond. The benchmark shows a direct dependence of the catalytic efficiency with the electronic effect of −X, which is confirmed by theoretical assessment of the intrinsic silylicities Π of hydridoiridium(III)‐silylium adducts and by the theoretical evaluation of the propensity of hydridospecies to transfer the hydrido ligand to the activated substrate. The revisited analysis of the Ir−Si−H interactions shows that the most cohesive bond in hydridoiridium(III)‐silylium adducts is the Ir−H one, while the Ir−Si is a weak donor‐acceptor dative bond. The Si…H interaction in all the cases is noncovalent in nature and dominated by electrostatics confirming the heterolytic cleavage of the hydrosilane's Si−H bond in this key catalytically relevant species.