Synthesis, Structure, and Reductive Elimination of Cationic Monoarylpalladium(IV) Complexes Supported by a Tripodal Oxygen Ligand

Cationic monoaryl–Pd IV complexes supported by the Kläui tripodal ligand [Co(η 5 ‐C 5 H 5 ){P(O)(OEt) 2 } 3 ] – (L OEt – ) were synthesized, and their reductive elimination was studied. Treatment of trans ‐[Pd(PPh 3 ) 2 (Ar)(I)] and [{Pd(η 2 ‐ppy t Bu)Cl} 2 ] [ppy t BuH = 2‐(4‐ tert ‐butylphenyl)pyridine] with [AgL OEt ] afforded [Pd(Ar)(PPh 3 )(η 2 ‐L OEt )] [Ar = Ph ( 1 ), p ‐tolyl ( 2 )] and [Pd(η 2 ‐ppy t Bu)(η 2 ‐L OEt )] ( 3 ), respectively. Chlorination of 1 , 2 , and 3 with PhICl 2 in the presence of NH 4 PF 6 afforded the cationic aryl–Pd IV chloride complexes [Pd(Ph)(PPh 3 )(Cl)(L OEt )](PF 6 ) ( 4 ), [Pd( p ‐tolyl)(PPh 3 )(Cl)(L OEt )](PF 6 ) ( 5 ), and [Pd(η 2 ‐ppy t Bu)(Cl)(L OEt )](PF 6 ) ( 6 ), respectively. Complexes 4 and 5 underwent C(sp 2 )–Cl elimination at 40 °C in acetonitrile to give a Pd II –L OEt species and the corresponding chloroarene. On the other hand, the C(sp 2 )–Cl elimination of 6 occurred at room temperature and afforded a Pd II species, presumably [Pd(Clppy t BuH)(L OEt )](PF 6 ), which further reacted with PhICl 2 to yield [Pd(η 2 ‐Clppy t Bu)Cl(L OEt )](PF 6 ) ( 7 ) [Clppy t BuH = 2‐(4‐ tert ‐butyl‐2‐chlorophenyl)pyridine]. The structures of complexes 1 , 4 , 6 , and 7 were established by X‐ray crystallography.