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 CC bond of P,P,P-diphenylvinyl iminophosphoranes yielded a new class of N,N-bidentate ligands R1–NP(Ph2)CH2CH2–NR2R3(2). These mixed nitrogen–nitrogen donor ligands react with stoichiometric amounts of PdCl2(PhCN)2 to give N,N-palladium complexes 3 containing an iminophosphorane moiety. From primary amines and two vinyl iminophosphorane units, either identical or different, the new terdentate ligands R1–NP(Ph2)CH2CH2–N(R3)–CH2CH2P(Ph2)N–R2(4), where R1= R2 or R1 R2, 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–NP(Ph2)CH2CH2PPh2) (9) and N,S-bidentate (R–NP(Ph2)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.