Tuning the hemilabile behaviour of a thioether–pyrazole ligand on Pd(II) complexes with diphosphines

The coordination mode of thioether–pyrazole ligand, 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane (bdtp) and 1,8-bis-(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) ligands, in Pd(II) complexes containing a diphosphine ligand is determined by subtle changes in size of the bridge between the two phosphorus atoms. The 1H NMR and 31P{1H} NMR at variable temperature in acetonitrile solution prove that the hemilabile character of the bdtp ligand depend on the diphosphine ligand. Thus, while in [Pd(bdtp)(dppe)](BF4)2[1](BF4)2 the thioether group not participate in the Pd(II) coordination sphere, two isomers with different coordination (P2N2 vs P2NS) are in equilibrium in [Pd(bdtp)(dppp)](BF4)2[2](BF4)2 acetonitrile solution. For complexes [Pd(bddo)(dppe)](BF4)2[3](BF4)2 and [Pd(bddo)(dppp)](BF4)2[4](BF4)2, only the coordination N,N is observed.