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

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.