The organophosphonous-N-(N′,N′,N″,N″-tetramethyl)guanidinide fluorides RP(F)N=C(NMe2)2 2a (R = t-Bu) and 2b (R = Ph) were synthesized. They are readily oxidized by the urea-H2O2 1:1 adduct and by elemental sulfur, selenium and tellurium to give the compounds 4a/b, 5a/b, 6a/b and 7a/b respectively. Compound 2b undergoes a Staudinger reaction with triphenylmethyl azide to yield the phosphine imide 3. The compounds were characterized by 1H-, 13C-, 19F and 31P NMR spectroscopy, and 6a/b and 7a/b by 77Se and 125Te NMR spectroscopy. The structures of the sulfur compound 5b and the selenium compound 6a were confirmed by X-ray crystal structure analysis. Both molecules exhibit short P-N-bonds [158.9(2) pm and 159.8(3) pm] consistent with partial double bond character even though the P(:S) and the P(:Se) bonds are not longer than a normal double bond.
