2728-67-8Relevant academic research and scientific papers
Stable phosphinous acids
Hoge, Berthold,Neufeind, Stefan,Hettel, Sonja,Wiebe, Waldemar,Th?sen, Christoph
, p. 2382 - 2387 (2007/10/03)
The electronic properties of organyl element compounds are strongly influenced by the electronic characteristics of the organic substituents. The bonding of two CF3 groups to a phosphorus atom effects a drastically decreased basicity. That is the phosphorus atom is the least basic centre in the compound (CF3)2POH. This compound, synthesized in 1960 by Burg and Griffiths, is the only known example of a phosphinous acid, although there should be a general interest in this class of compounds. However, only a few investigations have been reported which may be explained by the tedious and risky synthesis. In this paper a safe one step and high yield synthesis of (CF3)2POH is described. The compound (C6F 5)2POH, originally claimed as a phosphinous acid, is proved to exist at room temperature exclusively in the tautomeric oxide form. (C6F5)2P(O)H crystallizes in the triclinic space group P1? (no. 2) with a 992.9(1) pm; b 1501.9(2) pm; c 1539.4(2) pm; α 117.48(1)°; β 100.39(1)°; γ 96.02(1)° and Z 6. Quantum chemical investigations prove the electron withdrawing effect of s-triazinyl groups (1,3,5-triazin-4-yl derivatives) to be much stronger than that of pentafluorophenyl groups. Quantum chemical calculations at the B3PW91/6-311G(3d,p) level of theory predict for the bis(s-triazinyl) derivative (C3N3H2)2POH the phosphinous acid isomer to be favored by ΔEZP = 22 kJ/mol in relation to the corresponding phosphane oxide isomer. The phosphinous acid (CF3) 2POH (Cs symmetry) is favored at the same level of theory by about ΔEZP = 14 kJ/mol compared with the phosphane oxide structure (Cs symmetry).
Trimethylsilyl esters of phosphorus acids. III. Esters of difluoro- and bis(trifluoromethyl)phosphinous and -thiophosphinous acids
Cavell,Leary,Sanger,Tomlinson
, p. 1374 - 1380 (2008/10/08)
The esters R2PESi(CH3)3 (R = F, E = O; R = CF3, E = O, S) have been prepared using one or more of four synthetic routes (CF3)2PSSi(CH3)3 is the first known example of a PIII-S-Si bridged compound, but the analogous difluoro ester F2PSSi(CH3)3 appears to be thermally unstable at 25°. Attempted syntheses of the P(V) isomers R2P(E)Si(CH3)3 gave only the P(III) forms, indicating that these systems are susceptible to anti-Arbuzov rearrangements. The difference in the stability and polarity between the P-O-Si and P-S-Si bridge units was demonstrated by the reactions of the esters with HCl and (CH3)2NH. At least three different reactions of the esters with dimethylamine were observed: cleavage at the E-Si bond with or without concomitant subsequent reaction of (CH3)3SiN(CH3)2 with the ionic product R2PE- and, in the case of (CF3)2POSi(CH3)3, displacement of CF3H to yield CF3[N(CH3)2]POSi(CH3)3. The latter phosphine showed a temperature-dependent nmr spectrum consistent with conformational isomerism of the N(CH3)2 group.
