Roxana M. Bîrzoi

Di(phosphavinyl) ethers (2,4-diphospha-3-oxapentadienes)

Hydrolytic cleavage of the P-chlorophosphaalkenes (RMe2Si)2C=PCl (R = Me: 1a; R = iPr: 1b) in the presence of triethylamine leads to di(phosphavinyl) ethers (2,4-diphospha-3-oxapentadienes) [(RMe2Si)2C=P]2O (2a, 2b) as main products, accompanied by alkylphosphinic acids (RMe2Si)2(H)CP(H)(O)OH (3a, 3b). The hydrolysis of (PhMe2Si)2C=PCl (1c) proceeds less selectively. Reactions with metal oxides under aprotic conditions provide 2a [impure, from 1a with (nBu3Sn)2O] and 2b [from iodophosphaalkene (iPrMe2Si)2C=PI with Ag2O] as oils. 1H, 13C, 29Si and 31P NMR spectra, however, allow unambiguous characterisation of 2a and 2b. Formation mechanisms, structure, and C=P-O π stabilisation of the oxabisphosphaalkene [(H3Si)2C=P]2O (2ʹ) were studied with DFT methods. The double [2+4] cycloaddition reaction of 2a with two equivalents of cyclopentadiene leads to the phosphinous anhydride 7 as a mixture of diastereomers whereas the addition of two equivalents of tetrachloro-o-benzoquinone proceeds in a diastereoselective fashion. An X-ray crystal structure determination of the resulting oxo-bridged bis(2-phospha-2,5-dioxa-3,4-benzophospholene) derivative 8 revealed the presence of a racemic mixture of (R,R)- and (S,S)-configurated molecules. The solid state structure of a by-product, bisylphosphonic tetrachlorocatechol monoester (Me3Si)2CH-P(=O)(OH)-o-OC6Cl4OH 9, was also determined crystallographically. Graphical Abstract Di(phosphavinyl) Ethers (2,4-Diphospha-3-oxapentadienes)

P-functional phosphaalkenes with C-isopropyldimethylsilyl groups, and a sterically stabilized P-cyano phosphaalkene

GRAPHICAL ABSTRACT ABSTRACT The dehydrochlorination of the dichlorophosphane (iPrMe2Si)2C(H)PCl2 (2) with 1,4-diazabicyclo[2.2.2]octane (DBO) provides the P-chlorophosphaalkene (iPrMe2Si)2C=PCl (3). Halide exchange reactions of 3 with AgBF4, with Me3SiBr, and with Me3SiI lead to the P-halogenophosphaalkenes (iPrMe2Si)2C=PX (X = F: 4; X = Br: 5; X = I: 6). From the reaction of 3 with AgCN, the sterically stabilized P-cyanophosphaalkene (iPrMe2Si)2C=P-CN (7) was isolated. The structures of the related P-fluorenylphosphaalkene 9 (from 3 with fluorenyllithium) and of the P-selenophosphaalkenes (iPrMe2Si)2C = PSe(2,4,6-tBu3C6H2) (10) and [(iPrMe2Si)2C=P]2Se (11) were determined by X-ray crystallography.