PUB - Publikationen an der Universität Bielefeld

The reaction of the carbonyl-functionalized phosphaalkenes RC(O)P=C(NMe2)(2) [R = tBu (2a), Ph (2b)] with protic acids and alkylating reagents occurred at the two-coordinate phosphorus atom to give the phosphanyl-substituted carbocations 3a,b and 4a,b. In contrast, treatment with Me3SiOSO2CF3 resulted in attack at the oxygen atom by the silyl group, and the formation of [RC(OSiMe3)=PC(NMe2)(2)]SO3CF3 (5a,b). Similarly, the Lewis acids B(C6F5)(3), Al(tBu)(2)Cl and AlMe3 were ligated to the oxygen atom of the carbonyl group. Two equivalents of GaMe3 were added to the oxygen and phosphorus atom of the phosphaalkene to yield the thermolabile complexes [RC(OGaMe3)=P(GaMe3)C(NMe2)(2)] (10a,b). In contrast, one molecule of InMe3 was bound to the phosphorus center of the phosphorus compound. Reaction of the phosphaalkenes with [Ni(CO)(4)], [Fe-2(CO)(9)] or [{(Z)-cyclooctene}Cr(CO)(5)] also took place at the pnictogen atom, resulting in complexes of the type [RC(O)P{M(CO)(n)}C(NMe2)(2)] (R = tBu, Ph; M = Ni, n = 3; Fe, n = 4; Cr, n = 5). The chemical transformations reported here underline the versatile chemistry of phosphaalkenes and emphasize a relationship between carbonyl-functionalized phosphaalkenes and the well-investigated class of phosphorus ylides. X-ray structures of compounds 6b, 7b*, 10a, 11a and 12a are reported.