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

Abstract

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 σN,σN-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.