Organometallic Chemistry of Amidate Complexes. Accelerating Effect of Bidentate Ligands on the Reductive Elimination of <i>N</i>-Aryl Amidates from Palladium(II)

We report a series of arylpalladium complexes of acetamidate, sulfonamidate, and deprotonated oxazolidinone ligands that undergo reductive elimination with rates and yields that depend on the binding mode of the ancillary and amidate ligands. Complexes of the acetamidate ligands containing the bidentate phosphines DPPF and Xantphos as ancillary ligands undergo reductive elimination. The rate and yield were higher from the complex ligated by Xantphos, which contains a larger bite angle. In contrast, the analogous amidate complex containing a single sterically hindered monodentate ligand and a κ2-bound amidate ligand does not undergo reductive elimination. This trend of faster reductive elimination from complexes containing bidentate ancillary ligands than from a complex with a single monodentate ancillary ligand is unusual and is consistent with an effect of the denticity of the ancillary ligand on the binding mode of the amidate. Complexes of sulfonamidate ligands underwent reductive elimination faster than complexes of acetamidates, and reductive elimination occurred from complexes containing both bidentate and monodentate ancillary ligands. Like reductive elimination from the acetamidate complexes, reductive eliminations from the sulfonamidate complexes were faster when the complexes possessed bidentate Xantphos and κ-sulfonamidate ligands.本研究报道了一系列基于乙酰胺根（acetamidate）、磺酰胺根（sulfonamidate）及去质子化恶唑烷酮配体的芳基钯配合物，这类配合物的还原消除反应速率与产率取决于辅助配体与酰胺根配体的配位模式。以双齿膦配体双(二苯基膦基)二茂铁（DPPF）和Xantphos作为辅助配体的乙酰胺根钯配合物，可发生还原消除反应；其中使用具有更大咬角（bite angle）的Xantphos作为辅助配体的配合物，其还原消除的速率与产率更高。与之相反，仅含空间位阻型单齿配体（monodentate ligand）与κ²配位酰胺根配体的同类酰胺根钯配合物，无法发生还原消除反应。相较于仅含单齿辅助配体的配合物，含双齿辅助配体的配合物还原消除速率更快，这一趋势较为罕见，且与辅助配体的齿合度（denticity）对酰胺根配体配位模式的影响相符。磺酰胺根钯配合物的还原消除反应速率高于乙酰胺根钯配合物，且无论辅助配体为双齿还是单齿，磺酰胺根钯配合物均可发生还原消除反应。与乙酰胺根钯配合物的还原消除反应规律一致，当磺酰胺根钯配合物采用双齿Xantphos配体与κ配位磺酰胺根配体时，其还原消除速率更快。