Synthesis of Novel Phosphaalkene-Based Bidentate Ligands Mes*PCH(3-R-Ar) (R = Pyridyl, Carbaldimino) and Formation of Three-Membered Palladacycles Mes*(Me)P−CH(3-R-Ar)−PdCl by Carbapalladation of the PC Double Bond

Novel functionalized phosphaalkene-based bidentate ligands of the type 1-[( E ) - Mes*P C(H)]-3-R-benzene ( 8, R = N -phenylcarbaldimino; 2, R = 2-pyridyl; Mes* = 2,4,6-tri- tert -butylphenyl) were prepared via a Pd(0)-catalyzed cross-coupling reaction of ( Z ) - bromophosphaalkene ( Z ) - 1 with Grignard reagents. The reaction of 8 and 2 with MePdCl(COD) furnished three-membered phosphapalladacycles of the type ( 9, R = N -phenylcarbaldimino; 10, R = 2-pyridyl), displaying intramolecular coordination between the phosphine ligand and palladium(II). The structure of 10 was established by an X-ray structure determination, showing a dimeric structure. The addition of triphenylphosphine to 9 and 10 causes rupture of the interconnecting Pd−N bonds, furnishing 11 and 12, respectively.