Preparation, characterization, and structure of functionalized fluorophosphaalkenes of the type R3E-P=C(F)NEt2 (R/E = Me/Si, Me/Ge, CF3/Ge, Me/Sn)

P-functionalized 1-diethylamino-1-fluoro-2-phosphaalkenes of the type R3E-P =C(F)NEt2 [R/E = Me/Si (2), Me/Ge (3), CF3/Ge (4), Me/Sn (5)] are prepared by reaction of HP=C(F)NEt2 (1, E/Z = 18/82) with R3EX (X = I, Cl) in the pr esence of triethylamine as base, exclusively as Z-Isomers. 2-5 are thermola bile, so that only the more stable representatives 2 and 4 can be isolated in pure form and fully characterized. 3 and 5 decompose already at temperat ures above -10 degrees C, but are clearly identified by F-19 and P-31 NMR m easurements. The Z configuration is established on the basis of typical NMR data, an X-ray diffraction analysis of 4 and ab initio calculations for E and Z configurations of the model compound Me3Si-P=C(F)NMe2. The relatively stable derivative 2 is used as an educt for reactions with pivaloyl-, adam antoyl-, and benzoylchloride, respectively, which by cleavage of the SI-P b ond yield the push/pull phosphaalkenes RC(O)-P=C(F)NEt2 [R = tBu (6), Ad (7 ), Ph (8)], in which pi-delocalization with the P=C double bond occurs both with the lone pair on nitrogen and with the carbonyl group.