Tandem Deoxygenative Hydrosilation of Carbon Dioxide with a Cationic Scandium Hydridoborate and B(C6F5)3

A scandium hydridoborate complex supported by the dianionic pentadentate ligand B₂Pz₄Py is prepared via hydride abstraction from the previously reported scandium hydride complex with tris-pentafluorophenyl borane. Exposure of [(B₂Pz₄Py)Sc][HB(C₆F₅)₃] to CO₂ immediately forms [(B₂Pz₄Py)Sc][HCOOB(C₆F₅)₃] at room temperature. The formatoborate complex can also be synthesized directly from the starting material (B₂Pz₄Py)ScCl with Et₃SiH and B(C₆F₅)₃ while in the presence of an atmosphere of CO₂ in 81% yield. This compound was evaluated as the transition metal component of a tandem deoxgenative CO₂ hydrosilation catalyst. At 5% loadings, complete consumption of Et₃SiH was observed along with CO₂ reduction products, but conversion to an inactive scandium complex identified as (B₂Pz₄Py)ScOSiEt₃ was observed