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Issue 11, 2013
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Palladium(II) complexes of pyrazolated thio/selenoethers: syntheses, structures, single source precursors of Pd4Se and PdSe nano-particles and potential for catalyzing Suzuki–Miyaura coupling

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Abstract

The reactions of 4-bromo-1-(2-chloroethyl)-1H-pyrazole prepared from 4-bromopyrazole with the in situ generated PhSNa, PhSeNa, Na2S and Na2Se have resulted in thio/selenoether ligands L1–L4 respectively. The complexes [PdL1/L2Cl2](1–2) and [PdL3/L4Cl]BF4 (3–4) of these ligands have been synthesized by reacting them with [PdCl2(CH3CN)2] in CH3CN at 70 °C. The L1–L4 and their complexes (1–4) have been characterized with spectroscopic techniques viz.1H, 13C{1H} and 77Se{1H} NMR, IR and HR-MS. Single crystal structures of 1–4 determined by X-ray diffraction reveal nearly square planar geometry around Pd in each case. Thermally stable, moisture/air insensitive complexes 1–4 have been found to be efficient pre-catalysts for Suzuki–Miyaura coupling reactions (yield up to 96% in 2 h). Nano-particles (NPs) (size ∼3–19 nm) were formed in the beginning of these reactions. They are composed of Pd and S or Se with more % of Pd. These NPs also catalyze Suzuki coupling and appear to play an important role in catalysis. Single source one pot synthesis of Pd4Se and PdSe NPs (size ranges ∼8–26 nm), capped with trioctylphosphine (TOP), has been developed by thermolysis of 2 and 4 at 200–250 °C in TOP. HR-TEM, SEM, SEM-EDX and powder XRD have been used to authenticate these nano-particles. The NPs of PdP2 are formed when attempts were made to prepare nano-sized phases of palladium-sulfide by thermolysis of 1 and 3 in TOP.

Graphical abstract: Palladium(ii) complexes of pyrazolated thio/selenoethers: syntheses, structures, single source precursors of Pd4Se and PdSe nano-particles and potential for catalyzing Suzuki–Miyaura coupling

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Publication details

The article was received on 29 Aug 2012, accepted on 13 Dec 2012 and first published on 13 Dec 2012


Article type: Paper
DOI: 10.1039/C2DT31975F
Citation: Dalton Trans., 2013,42, 3908-3918
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    Palladium(II) complexes of pyrazolated thio/selenoethers: syntheses, structures, single source precursors of Pd4Se and PdSe nano-particles and potential for catalyzing Suzuki–Miyaura coupling

    K. N. Sharma, H. Joshi, V. V. Singh, P. Singh and A. K. Singh, Dalton Trans., 2013, 42, 3908
    DOI: 10.1039/C2DT31975F

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