Kinetics Using PhSi(OiPr)H2. To further investigate the role of silane in determining the rate, we tested PhSi(OiPr)H2, which was previously reported by Shenvi and coworkers to be highly active in mHAT reactions. We found that replacing PhSiH3 with PhSi(OiPr)H2 significantly increases the rate of cHAT olefin hydrogenation, achieving the same >90% yield in 15 minutes rather than 8 hours. This finding supports the hypothesis that silane is involved in the turnover-limiting step of the catalytic reaction.