528584-61-4Relevant academic research and scientific papers
Intramolecular dehydrofluorinative coupling of the asymmetric diphosphine Ph2PCH2CH2PPh(C5F4N-4) and pentamethylcyclopentadienyl ligands in a rhodium complex
Bellabarba, Ronan M.,Nieuwenhuyzen, Mark,Saunders, Graham C.
, p. 1802 - 1810 (2003)
The tetrafluoropyridyl-substituted diphosphine Ph2PCH2CH2PPh(C5F4N-4) (1) has been prepared in three steps from dppe. Comparison of the spectroscopic properties between trans-[RhCl(CO){PPh2(C5F4N-4)}2] and analogous complexes of other fluorinated triaryl phosphines reveals the lower basicity of tetrafluoropyridylphosphines relative to pentafluorophenylphosphines. The reaction between [Cp*RhCl(μ-Cl)]2 and 1 in the presence of [BF4-] yielded racemic diastereoisomers of [Cp*RhCl(1)][BF4]. In the SRhRP and RRhSP pair of enantiomers the Cp* and tetrafluoropyridyl groups have a cis disposition about the Rh-P bond, and in the SRhSP and RRhRP pair the groups are trans. In situ NMR experiments reveal that the cis pair, in which the Cp* and tetrafluoropyridyl groups are close, underwent rapid dehydrofluorinative C-C coupling to give the respective enantiomers of [{η5,κP,κP-C5Me4CH2- 2-C5F3N-4-PPhCH2CH2 PPh2}RhCl][BF4] (6·[BF4]). The trans pair did not undergo coupling, but isomerized to the cis pair on heating in ethanol. The reaction between [Cp*RhCl(μ-Cl)]2 and 1 in refluxing benzene afforded 6·[BF]4 in 64% yield after anion metathesis. The structures of OPPh2-(C5F4N-4), the cis isomer of [Cp*RhCl(1)][BF4], and one enantiomer of 6·[BF4], which crystallizes as a conglomerate, have been determined by single-crystal X-ray diffraction.
