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Synthesis, structure and reactivity of anionic tripalladium cluster compounds

1992; Royal Society of Chemistry; Issue: 12 Linguagem: Inglês

10.1039/dt9920001939

2050-5671

Andrew D. Burrows, Jonathan C. Machell, D. Michael P. Mingos,

Organometallic Complex Synthesis and Catalysis

The cluster compounds R+[Pd3(µ-SO2)2(µ-X)(PPh3)3]–[R = NEt4, X = Cl 1 or Br 2; R = NEt3(CH2Ph), X = Cl 3; R = PPh3(CH2Ph), X = Cl 4; R = NBu4, X = I 5] have been synthesised from the reaction of [Pd5(µ-SO2)2(µ3-SO2)2(PPh3)5] and R+X–. The molecular structure of [NEt3(CH2Ph)][Pd3(µ-SO2)2(µ-Cl)(PPh3)3]·0.5Me2CO has been determined by single-crystal X-ray diffractometry. The study, though limited by disorder of the bridging ligands, has demonstrated that the Pd–Pd bond distances are within the expected range for a 44-electron triangulo-palladium cluster. These triangulo-cluster compounds undergo a variety of reactions: one SO2 ligand may be substituted by NO+, giving the neutral triangulo cluster [Pd3(µ-NO)(µ-SO2)(µ-Cl)(PPh3)3]6 which has been characterised by 31P-{1H} NMR spectroscopy and fast atom bombardment mass spectrometry. The triangle may be capped by the metal fragments Au(PPh3)+ and Tl+, giving [Pd3Au(SO2)2Cl(PPh3)4]7 and [Pd3Tl(SO2)2Cl(PPh3)3]8 respectively and the chloride ligand may be abstracted by AgNO3 leading by cluster aggregation to [Pd5(µ-SO2)2(µ3-SO2)2(PPh3)5]. The compound [Pd3(SO2)2X(PPh3)3]– reacts in a reversible manner with SO2 to give [Pd3(SO2)3X(PPh3)3]–(X = Cl 9 or I 10). The reversibility of this reaction and the greater stability of the adduct formed from the iodo-triangulo-palladium cluster suggested that the additional SO2 ligand is co-ordinated to the halide ligand.