Structure elucidation of the unprecedented asymmetric bis-chelate complex [Pd(1,3-bis(di(o-methoxy-m-methylphenyl)phosphino)propane)2]2+ in the solid state and in solution

Abstract

Complexes of the type [Pd(ligand)₂](anion)₂ were prepared with a series of bidentate di(o-methoxyphenyl)phosphine ligands with increasing steric bulk on the meta position of the phenyl groups: m-H (L1); m-MeO (L2); and m-Me (L3). The solid-state structure of [Pd(L2)₂](OTs)₂ revealed that the two ligands are symmetrically coordinated to Pd²⁺. In the solid state structure of [Pd(L3)₂](OTs)₂ however, the two ligands are unsymmetrically coordinated to Pd²⁺, yielding an unprecedented conformation of this bis-chelate P₄Pd²⁺ complex. ¹H-¹H-COSY and NOESY analysis and a ³¹P-NMR simulation showed that the asymmetric structure of [Pd(L3)₂](OTs)₂ is retained in solution.