Dinuclear PdII/PtII complexes [M2(phosphine)n(thio-ligand)3]Cl incorporating N,S-bridged pyridine-2-thiolate and benzimidazoline-2-thiolate

Abstract

Equimolar reaction of [PdCl2(dppm)] {dppm=bis(diphenylphosphino) methane} with pyridine-2-thione (pySH) in presence of NaOH base in aqueous ethanol formed dinuclear mixed-ligand complex, [PdII2(μ-κ2:N,S-pyS)3(μ-P,P-dppm)]Cl 1. Similarly, reaction of PdCl2(PPh3)2 with benzimidazoline-2-thione (bzimSH) in 1:2M ratio in the presence of Et3N base in acetonitrile has formed a dinuclear complex, [PdII2(μ-κ2:N,S-bzimS)2(κ1-S-bzimS)(PPh3)3]Cl·2H2O 2. Surprisingly, analogous thio-ligand, 1,3-imidazoline-2-thione (imzSH), merely formed a simple square planar complex, [Pd(κ1-S-imzSH)4]Cl2·2H2O 3. The reaction of H2PtCl6 with pySH and dppm (1:1:1M ratio) in the presence of Et3N base in toluene–ethanol (1:1:: v/v) mixture also formed a mixed-ligand dinuclear complex [PtII2(μ-κ2:N,S-pyS)3(μ-P,P-dppm)]Cl similar to 1. All these complexes have been characterized using analytical data, IR, NMR (1H, 31P), UV–vis, fluorescence, ESI-mass and single crystal X-ray crystallographic techniques. The anionic thio-ligands are N,S-bridged in complexes 1 and 4, both N,S-bridged and κ1-S bonded in 2 and as neutral κ1-S bonded in 3. There are short M⋯M contacts in 1 and 4 (1: 2.7249(5) Å; 4: 2.7350(8) Å). Complexes 1, 3 and 4 showed intense fluorescence. ESI mass spectral studies of 1, 3 and 4 revealed the formation of molecular ions and other species.