Preparation, Structural Analysis, and Reactivity Studies of Phosphenium Dications

Abstract : This work expands on the recent synthesis and reactivity of the two-coordinate P(III)-containing dication [((Ph3P)2C)P(NiPr2)]2+ (3a(2+)). Two additional dications of general formula [((RPh2P)2C)P(NR′2)](2+) (3b(2+), R = 1/2 (CH2)3, R′ = iPr; 3c(2+), R = Ph, R′ = Cy) have been prepared. Solution and solid-state 31P NMR isotropic shifts for this dication class were observed around 360 ppm. Except for [3a][SbF6]2, the 31P CP/MAS NMR spectra reveal a high degree of structural disorder around the dicationic site in the solid state. Surprisingly, the synthesis of dication 3a(2+) was only possible in the presence of AlCl4(–), SbF6(–), and substituted tetraarylborates, while the use of ClO4(–), OTf(–), BF4(–), PF6(–), and BPh4(–) resulted in complex product mixtures. Single-crystal X-ray analysis of dications 3a(2+) and 3c(2+) suggested a 4π allyl-like structure for the central CPN fragment, and this has been supported through detailed theoretical investigations. Initial reactivity studies between dications 3a(2+)/3c(2+) and PMe3 show an equilibrium between the free dication and the target adduct. Furthermore, 3a(2+) has been shown to be capable of O–H bond activation using water and methanol and polymerizes THF when it is dissolved in this solvent.
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Madelin Qin Yi Tay, Gordana Ilic, Ulrike Werner-Zwanziger, Yunpeng Lu, Rakesh Ganguly, et al.. Preparation, Structural Analysis, and Reactivity Studies of Phosphenium Dications. Organometallics, American Chemical Society, 2016, 35, pp.439-449. ⟨10.1021/acs.organomet.5b00763⟩. ⟨hal-01226258⟩



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