Initial Kinetic Analysis Using PhSiH3. The reaction orders in the observed rate law for the achiral cHAT olefin hydrogenation reaction (Figure ) were evaluated by monitoring product formation using GC. We used two complementary methods to increase our confidence about the conclusions. The first was to assess the entire reaction course graphically with variable time normalization analysis (VTNA). The second was to use initial rates. Employing each kinetic technique, the order of the rate dependence on PhSiH3 is less than 1 and can be reasonably fit to a fractional 0.5 order dependence (Figure for VTNA, see SI for initial rate data). The non-integer dependence on [PhSiH3] did not consistently approach 0 or 1 when [PhSiH3] was varied over the catalytically relevant concentration range of 0.1 to 0.4 M. The rate dependences on [olefin] and [thiol] were found to be zero order.