New phosphino-oxazoline and related phosphino-iminolate palladium complexes; structure of an unusual zwitterionic dinuclear Pd(II) complex

Reaction of the phosphino-oxazoline chiral ligand (4-(R)-phenyl-2-oxazoline-2-ylmethyl)diphenylphosphine) ( abbreviated (R)-PCH(2)ox(Ph)) with [Pd(dmba-C,N)(mu-Cl)](2) or [PdCl2(cod)] (cod = 1,5-cyclooctadiene) led to the formation of [Pd(dmba-C, N){(R)-PCH(2)ox(Ph)-kappa(2)P,N}]Cl 1 and [PdCl2{(R)-PCH(2)ox(Ph)-kappa(2)P,N}] 5, respectively. Deprotonation of the palladium phosphino-oxazoline complex 1 occurred at the PCH2 group and resulted in the formation of an anionic P, N chelate with a prochiral carbon atom in [Pd(dmba-C,N){(R)-PCHox(Ph)-kappa(2)P,N}] 2. Reaction of 2 with [Pd(dmba-C,N)(mu-Cl)](2) led to the unexpected and diastereoselective formation of the dinuclear complex [{Pd(dmba-C,N)Cl}-(R)-{CHPPh2-(R)-ox(Ph)}Pd(dmba-C,N)] 4 in which a Pd(dmba-C,N)Cl moiety is directly bonded to the carbon a to the P atom of the anionic P, N chelate of 2. This results in an unusual zwitterionic structure. In the course of this work, crystals of [(dmba-C,N)Pd(mu-OH)(mu-Cl)Pd(dmba-C,N)].1/2[Pd(dmba-C,N)(mu-Cl)](2) 7 were obtained and the single crystal X- ray analyses of complexes 2,4.2THF,5.CH2Cl2, [PdCl(Me){(R)-PCH(2)ox(Ph)-kappa(2)P,N}] 6 and 7 are presented.