Exploring the versatility of N-pyrazole, P-phosphinite hybrid ligands against Pd(II). From monomers and dimers to one-dimensional chain, two-dimensional layer polymers and three-dimensional networks

The versatility of N-pyrazole, P-phosphinite hybrid ligands [2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L1), 3-(3,5-dimethyl-1H-pyrazol-1-yl)propyldiphenylphosphinite (L2), and 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L3)] has been studied toward Pd(II). The reactions lead to a mixture of three complexes in solution for each ligand ([PdCl2(Lx)], [PdCl 2(Lx)2] and [PdCl2(L x)]2) obtaining monomers (where L acts as mono-/bidentated agents) and dimers where the two L bridge the two metallic atoms in a head-to-tail arrangement. Complexes have been isolated and fully characterized by analytical and spectroscopic methods. X-ray crystal structures of some of the complexes as well as of other species [PdCl2L3] 2 (only detected in the solid state) are presented. Furthermore, these complexes were prepared to examine the effects of the L structure on the topology and interpenetration form (one-dimensional chain, two-dimensional layer polymers and three-dimensional networks). Additionally, experimental and simulated NMR studies and a battery of modifications in the synthesis of the complexes (relation ratio of the starting products, order of addition, solvents and temperature) permit a better understanding of the role of ligands in the self-assembly process. © 2012 American Chemical Society.