For benzonitrile as a substrate, we observe an inverse-firstorder dependency implying some inhibition occurs, potentially due to a competing reaction, however no evidence of binding of more than one equivalent of the nitrile to either Complex A or HBPin was observed spectroscopically (see Supporting Information). Saturation kinetics of HBpin was observed when increasing the concentration and a zero-order dependency over 0.5 M, which is consistent with B-H addition across the metal center not being part of the ratelimiting step.