Chlorobis(pentafluoroethyl)phosphane: Improved Synthesis and Molecular Structure in the Gas Phase

Abstract

(C(2)F(5))(2)PCl is now accessible through a significantly improved synthesis protocol starting from the technical product (C(2)F(5))(3)PF(2). (C(2)F(5))(3)PF(2) was reduced in the first step with NaBH(4) in a solvent-free reaction at 120 °C. The product, P(C(2)F(5))(3), was treated with an excess of an aqueous sodium hydroxide solution to afford the corresponding phosphinite salt Na(+)(C(2)F(5))(2)PO(-) selectively under liberation of pentafluoroethane. Subsequent chlorination with PhPCl(4) resulted in the selective formation of (C(2)F(5))(2)PCl, which was isolated by fractional condensation in an overall yield of 66 %. The gas electron diffraction (GED) pattern for (C(2)F(5))(2)PCl was recorded and found to be described by a two-conformer model. A quantum chemical investigation of the potential-energy surface revealed the possible existence of many low-energy conformers, each with a number of low-frequency vibrational modes and therefore large-amplitude motions. The conformer calculated to be most stable was also found to be most abundant by GED and comprised 61(5) % of the total. The molecular structure parameters determined by GED were in good agreement with those calculated at the MP2/TZVPP level of theory; the only significant difference was a discrepancy of about 3° in the C-P-C angle, which, for the lowest-energy conformer, was refined to 98.2(4)° and was calculated to be 94.9°.

Functionalized Bis(pentafluoroethyl)phosphanes: Improved Syntheses and Molecular Structures in the Gas Phase

“…Table 2 shows the O3LYP/aug-cc-pVTZ energies and abundances of the conformers; B3LYP/cc-pVTZ data are provided in the Supporting Information. Most of the conformers are structurally similar to those of (C 2 F 5 ) 2 -PCl, [4] the difference being that there is only one minimum for conformer II of (C 2 F 5 ) 2 PH instead of two very close lying minima on the PES for (C 2 F 5 ) 2 PCl (conformers 2 and 3 in the notation in ref. [4] ).…”

“…Most of the conformers are structurally similar to those of (C 2 F 5 ) 2 -PCl, [4] the difference being that there is only one minimum for conformer II of (C 2 F 5 ) 2 PH instead of two very close lying minima on the PES for (C 2 F 5 ) 2 PCl (conformers 2 and 3 in the notation in ref. [4] ). Hence, theory predicts two major conformers for (C 2 F 5 ) 2 PH whereas all the others have higher energies and abundances that are too low at the temperature of the GED study to be reliably detectable.…”

“…[3] Substitution of one pentafluoroethyl group by a sterically less demanding substituent leads to more complicated conformational behaviour, as has been demonstrated for (C 2 F 5 ) 2 PCl, which has also been studied by gas electron diffraction (GED). [4] Such compounds with sterically more accessible phosphorus atoms allow manifold coordination chemistry. A prominent example of this is the chelating ligand (C 2 F 5 ) 2 -PC 2 H 4 P(C 2 F 5 ) 2 with two P(C 2 F 5 ) 2 groups.…”

“…[11] Treating the iodo compounds with silver or mercury chloride furnishes the corresponding chloro derivatives. [12] Recently published, significantly improved syntheses of (C 2 F 5 ) 2 PCl [4] and (C 2 F 5 ) 2 POH [13] start from the technical product (C 2 F 5 ) 3 PF 2 and proceed via P(C 2 F 5 ) 3 and (C 2 F 5 ) 2 PO -salts as intermediates, respectively. The improved protocol for the synthesis of (C 2 F 5 ) 2 POH has allowed the preparation of several stable and catalytically active transition-metal complexes.…”

Analysis of Volatile and Oxidation Sensitive Compounds Using a Cold Inlet System and Electron Impact Mass Spectrometry

“…Unfortunately, these methods allow not always for an unambiguous identification of a compound because they yield incomplete information, e.g., when elements such as chlorine or bromine are part of the molecule. Gas electron diffraction on the other hand is able to provide detailed information about the analyte, however, the method is very time consuming, sample preparation is difficult, and only few groups are able to conduct these analysis 13,14 . Here, the cold inlet system for the analysis of metal organyls, silanes, or phosphanes, susceptible to oxidation or hydrolysis by EI mass spectrometry is of great use for (in)organic chemists enabling the unambiguous identification of novel compounds by supplying them with information regarding the mass of a molecule and of characteristic fragment ions.…”