Synthesis and molecular structure of a new class of bi- and ter-dentate palladium complexes with iminophosphorane containing ligands

The Michael-type addition of a range of amines to the C=C bond of P,P,P-diphenylvinyl iminophosphoranes yielded a new class of N,N-bidentate ligands R-1-N=P(Ph-2)CH2CH2-NR2R3 (2). These mixed nitrogen-nitrogen donor ligands react with stoichiometric amounts of PdCl2(PhCN)(2) to give sigmaN,sigmaN-palladium complexes 3 containing an iminophosphorane moiety. From primary amines and two vinyl iminophosphorane units, either identical or different, the new terdentate ligands R-1-N=P(Ph-2)CH2CH2-N(R-3)-CH2CH2P(Ph-2)=N-R-2 (4), where R-1 = R-2 or R-1 not equal R-2, could be efficiently synthesized. Reaction of these ligands with 1.5 equiv. of PdCl2(PhCN)(2) yielded the cationic complexes 5 with the ligands coordinating in a N,N',N'-terdentate fashion. Additionally, by the use of other nucleophiles such as diphenylphosphane and thiophenol this methodology has been applied to the synthesis of the new N,P-(R-N P(Ph-2)CH2CH2PPh2) (9) and N,S-bidentate (R-N=P(Ph-2)CH2CH2SPh) (10) ligands, respectively, and of their corresponding Pd(II) complexes (11 and 12). All compounds have been characterized by spectroscopic methods and the X-ray crystal structures of 3c, 5b and 11b are reported.