Pyrazole‐Stabilized Dinuclear Palladium(II) Chalcogenolates Formed by Oxidative Addition of Bis[2‐(4‐bromopyrazol‐1‐yl)ethyl] Dichalcogenides to Palladium(II) – Tailoring of Pd–S/Se Nanoparticles

Abstract

AbstractBis[2‐(4‐bromopyrazol‐1‐yl)ethyl] disulfide and diselenide L1 and L2 were synthesized by the reactions of 4‐bromo‐1‐(2‐chloroethyl)‐1H‐pyrazole with the in situ generated Na2S2 and Na2Se2. The reactions of L1 and L2 with 2 equiv. of [PdCl2(CH3CN)2] in CH3CN at 70 °C proceed through an oxidative addition/reductive elimination sequence to the PdII center to form the chalcogenolato‐bridged dinuclear palladium(II) complexes [Pd2Cl2(μ‐EN)2] [1 (E = S) and 2 (E = Se); EN = 2‐(4‐bromopyrazol‐1‐yl)ethanechalcogenolate]. The reactions of 1 and 2 with CH3CN and AgBF4 resulted in the formation of [Pd2(CH3CN)2(μ‐EN)2]·2BF4 (3 and 4). Compounds L1, L2, and their complexes 1–4 have been characterized through 1H, 13C{1H}, and 77Se{1H} nuclear magnetic resonance (NMR) spectroscopy; infrared (IR) spectroscopy; and high‐resolution mass spectrometry (HRMS). The single‐crystal X‐ray structures of 2–4 have revealed distorted square‐planar geometries around the Pd center in each case. The Pd–S and Pd–Se bond lengths are in the ranges 2.277(2)–2.296(2) and 2.372(9)–2.3971(17) Å, respectively. Single‐source precursor routes for the synthesis of palladium chalcogenide nanoparticles (NPs) have been developed by the thermolyses of 1–4 in 1:1 mixtures of oleic acid (OA) and 1‐octadecene (ODE). Pd17Se15 NPs were formed from both PdII selenolates 2 and 4, whereas Pd4S NPs and a mixture of Pd16S7 (ca. 68 %) and PdS (ca. 32 %) NPs were obtained from PdII thiolates 1 and 3, respectively. Transmission electron microscopy (TEM), scanning electron microscopy with energy‐dispersive X‐ray spectroscopy (SEM‐EDX), and powder X‐ray diffraction (PXRD) have been used to authenticate the NPs. X‐ray photoelectron spectroscopy (XPS) studies on the NPs have revealed that there is a charge transfer from Pd to S/Se. The compositions of the NPs determined from XPS are consistent with the PXRD results.