Hybrid (Te, N) and (N, Te, N) ligands having pyrrolidine ring and their palladium(II) and mercury(II) complexes: synthesis and crystal structures

Abstract

Reactions of (2-choroethyl)pyrrolidine hydrochloride with ArTe− or Te2− generated in situ by borohydride reduction of Ar2Te2 or elemental tellurium give N-{2-(4-methoxyphenyltelluro)ethyl}pyrrolidine (L1) or bis{2-(pyrrolidine-N-yl)ethyl}telluride (L2), respectively, as viscous liquids, which are characterized by 1H- and 13C{1H}-NMR spectroscopy. The potentially bidentate hybrid organotellurium ligand (L1) reacts with HgBr2 and Na2PdCl4 to give complexes [HgBr2·L1] (1) and [PdCl2·L1] (2) respectively. The potentially tridentate ligand (L2) also forms a complex [HgBr2·L2] (3). All three complexes give characteristic 1H- and 13C{1H}-NMR spectra, although the deshielding of carbon atoms linked to Te/N as well as protons attached to them is small in the case of both Hg complexes. The single crystal structures of 1–3 have been solved. In 1 and 2 the ligand L1 coordinates via Te and N both with metal indicating that the pyrrolidine N has good ligating strength. The Pd---Te and Hg---Te bond lengths are 2.4781(3) and 2.747(1) Å, respectively. The Pd---Cl trans to Te (2.3915(7) Å) is longer than other Pd---Cl bond length. There are two independent molecules in the asymmetric unit of 3 that have essentially the same bidentate molecular structures. There is no evidence of significant intermolecular Hg---Br bonding. The Hg---Te bond in 3 (ave. 2.686(2) Å) is shorter than in 1. The potentially tridentate ligand L2 in complex 3 coordinates only as a bidentate donor. The molecular weights of 1 and 2 are close to double the formula weight indicating strong molecular association in solution. Te---C(alkyl) is somewhat longer than Te---C(aryl) for complexes 1 and 2.