The reaction chemistry of plutonyl(VI) chloride complexes with triphenyl phosphineoxide and triphenyl phosphinimine

摘要

The reaction between Ph_3PO dissolved in acetone and "PuO_2Cl_2" in dilute HCl resulted in the formation of [PuO_2Cl_2(Ph_3PO)_2]. Crystallographic characterization of the acetone solvate revealed the expected axial trans plutonyl dioxo, with trans Cl and Ph_3PO in the equatorial plane. Spectroscopic analyses (~(31)P NMR, ~1H NMR, and visIR) indicate the presence of both cis and trans isomers in solution, with the trans isomer being more stable. Confirmation of the higher stability of the trans versus cis isomers for [AnO_2Cl_2(Ph _3PO)_2] (An = U and Pu) was obtained through quantum chemical computational analysis, which also reveals the Pu-OTPPO bond to be more ionic than the U-O_(TPPO) bond. Slight variation in reaction conditions led to the crystallization of two further minor products, [PuO _2(Ph_3PO)_4][ClO_4]_2 and cis-[PuCl_2(Ph_3PO)_4], the latter complex revealing the potential for reduction to Pu~(IV). In addition, the reaction of Ph_3PNH with [PuO_2Cl_2(thf) _2]_2 in anhydrous conditions gave evidence for the formation of both cis-and trans-[PuO_2Cl_2(Ph _3PNH)_2] in solution (by ~(31)P NMR). However, the major reaction pathway involved protonation of the ligand with the crystallographic characterization of [Ph_3PNH_2] _2[PuO_2Cl_4]. We believe that HCl/SiMe _3Cl carried through from the small scale preparation of [PuO _2Cl_2(thf)_2]_2 was the source of both protons and chlorides. The fact that this chemistry was significantly different from previous uranium studies, where cis-/trans-[UO_2Cl _2L_2] (L = Ph_3PO or Ph_3PNH) were the only products observed, provides further evidence of the unique challenges and opportunities associated with the chemistry of plutonium.