Synthesis of New Chiral Bidentate Isonitrile–Acyclic Diaminocarbene Palladium(II) Compounds and Their Catalytic Activity

Five new chiral bidentate isonitrile–diaminocarbene
palladium­(II)
complexes (5a–5e) as well as the
bis-diaminocarbene complex 6 were prepared by metal-mediated
nucleophilic addition of amines to the corresponding bisisonitrile–palladium­(II)
compound 4. The new chelates were fully characterized
by 1D and 2D NMR experiments, IR, and ESI-MS. In addition, the X-ray
structure of 5a, 5c, and 6 could
be analyzed, showing different sterical properties. We furthermore
investigated the relationship between their structure and their catalytic
activity. The mixed ligand complexes 5a and 5c showed high activity both in Suzuki–Miyaura cross-coupling
and in intermolecular asymmetric allylic alkylation (AAA) reactions
as well as moderate chiral induction in the AAA.