Si–H Activation in an Iridium Nitrido ComplexA Mechanistic and Theoretical Study

Si–H activation in triethyl-
and triarylsilanes by a square-planar
pyridine-diimine iridium complex with a terminal nitrido unit leads
to the corresponding silyl amido complexes, which were unambiguously
characterized by X-ray crystallography. Based on detailed combined
kinetic and theoretical studies (DFT), direct addition of the Si–H
bond to the iridium nitrido unit is proposed. The electronic propensities
of the transition states for the Si–H activation were probed
with a Hammett series of para-substituted triarylsilanes
HSi­(C6H5)2(4-C6H4-X). Based on the combination of experimental and theoretical studies,
two independent pathways for this process are proposed, which point
toward an ambiphilic propensity of the nitrido unit. Alternative pathways
and the charge transfer in the transition states were also investigated.
Furthermore, the barriers for the related H–H and C–H
activation processes in dihydrogen and methane were analyzed.