PUB - Publikationen an der Universität Bielefeld

The reaction of the inversely polarized phosphaalkenes RP=C(NMe2)2 [R = tBu (1a), Cy (1b), 1-Ad (1c), Ph (1d), Mes (1e)] with an excess of diphenyl ketene in n-pentane affords the zwitterionic adduct (Me2N)(2)C-C(O)=CPh2 (2) and the 3,5-dibenzhydrylidene-1,4,2-dioxaphospholanes 4a-e. The reaction of la with Ph2C=C=O in concentrated acetonitrile solution gives 4a and 5-benzhydrylidene-2-tert-butyl-4,4-diphenyl- 1,2-oxaphospholan-3-one (6a) as a by-product. In contrast, treatment of Me3SiP=C(NMe2)(2) (1i) with the ketene leads to the formation of 2-phospha-1,3-butadiene (5). The thermolabile phosphaalkene 8 decomposes into an imid-azolylidene and (tBuP), the latter species spontaneously oligomerizes to (tBuP), (n = 3, 4). Obviously, compounds 1a-e serve as a convenient source of phosphinidenes and the carbene C(NMe2)(2). A Wanzlick-type equilibrium between these species, however, must be excluded according to exchange and cross-coupling experiments. The molecular structures of 2, 4e and 6a were determined by X-ray structure analyses. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.