96998-72-0Relevant academic research and scientific papers
Palladium clusters. 4. Synthesis and 31P and 195Pt NMR study of a mixed platinum/palladium cation, [PtPd2Cl(PPh2)2(PPh3) 3]+, and the crystal and molecular structures of [Pd3Cl(PPh2)2(PEt3) 3][BF4], [Pd ...
Berry, David Eric,Bushnell, Gordon William,Dixon, Keith Roger,Moroney, Pearse Mary,Wan, Ch'eng
, p. 2625 - 2634 (2008/10/08)
Full title: Palladium clusters. 4. Synthesis and 31P and 195Pt NMR study of a mixed platinum/palladium cation, [PtPd2Cl(PPh2)2(PPh3) 3]+, and the crystal and molecular structures of [Pd3Cl(PPh2)2(PEt3) 3][BF4], [Pd3Cl(PPh2)2(PPh3) 3][BF4], and [Pt0.81Pd2.19Cl(PPh2)2(PPh 3)3][BF4]. Reaction of [PdCl(PPh3)3][BF4] with [PtCl(PPh3)3][BF4] in tetrahydrofuran at 125°C gives [PtPd2Cl(PPh2)2(PPh3) 3][BF4], the first example of a mixed Pt/Pd cluster. X-ray diffraction study of this product shows that it crystallizes in the triclinic space group P1, with a = 15.746 (8) A?, b = 20.421 (8) A?, c = 13.045 (7) A?, α = 97.55 (5)°, β = 119.37 (4)°, and γ = 94.19 (5)°. The crystal also contained about 19% of [Pd3Cl(PPh2)2(PPh3) 3][BF4] with the extra palladium atoms distributed randomly over the platinum sites. X-ray diffraction results are also reported for the following two tripalladium clusters: [Pd3Cl(PPh2)2-(PEt3) 3][BF4], monoclinic P21/c, a = 16.141 (11) A?, b = 19.512 (8) A?, c = 16.912 (6) A?, β = 97.66 (6)°; [Pd3Cl(PPh2)2-(PPh3) 3][BF4], monoclinic P21/c, a = 15.486 (8) A?, b = 16.971 (7) A?, c = 27.542 (16) A?, β = 92.80 (9)°. The M3ClP5 heavy-atom core is similar in all three structures, with a triangle of metal atoms each bearing a terminal tertiary phosphine and with two edges bridged by diphenylphosphide and one bridged by chloride. The metal-metal lengths are relatively long, averaging 2.92 A? in the tripalladium clusters and 2.89 A? in the mixed species, but are clearly within bonding distance. Complete analysis and computer simulation of 31P{1H} and 195Pt[1H] nuclear magnetic resonance spectra show a highly shielded Pt atom (-1406.7 ppm relative to Ξ(195Pt) = 21.4 MHz), relatively large values (80-90 Hz) for the three-bond coupling between terminal phosphorus atoms, and extreme downfield shifts (+200 to +230 ppm relative to 85% H3PO4) for the bridging phosphorus atoms. These parameters are discussed in terms of the metal-metal bonding in the clusters, and a distinction is drawn between the deshielding effect of metal-metal bonds and the shielding effect of small angles at phosphorus in other small ring compounds.
