Pd(II) complexes containing N-alkyl-3-pyridine-5-trifluoromethyl pyrazole ligands: Synthesis, NMR studies and X-ray crystal structures

Abstract

Palladium [PdCl 2( L)] complexes with N-alkylpyridylpyrazole derived ligands [2-(5-trifluoromethyl-1 H-pyrazol-3-yl)pyridine ( L 1 ), 2-(1-ethyl-5-trifluoromethyl-1 H-pyrazol-3-yl)pyridine ( L 2 ), 2-(1-octyl-5-trifluoromethyl-1 H-pyrazol-3-yl)pyridine ( L 3 ), and 2-(3-pyridin-2-yl-5-trifluoromethyl-pyrazol-1-yl)ethanol ( L 4 ) were synthesised. The crystal and molecular structures of [PdCl 2( L)] ( L = L 2 , L 3 , L 4 ) were resolved by X-ray diffraction, and consist of monomeric cis-[PdCl 2( L)] molecules. The palladium centre has a typical square-planar geometry, with a slight tetrahedral distortion. The tetra-coordinate metal atom is bonded to one pyridinic nitrogen, one pyrazolic nitrogen and two chlorine ligands in cis disposition. Reaction of L ( L 2 , L 4 ) with [Pd(CH 3CN) 4](BF 4) 2, in the ratio 1M:2L, gave complexes [Pd( L)] 2(BF 4) 2. Treatment of [PdCl 2( L)] ( L = L 2 , L 4 ) with NaBF 4 and pyridine (py) and treatment of the same complexes with AgBF 4 and triphenylphosphine (PPh 3) yielded [Pd( L)(py) 2](BF 4) 2 and [Pd( L)(PPh 3) 2](BF 4) 2 complexes, respectively. Finally, reaction of [PdCl 2( L 4 )] with 1 equiv of AgBF 4 yields [PdCl( L 4 )](BF 4).