Phenyl cyanophosphide PhPCN-is formed in the reactions of P(CN); with phenyllithium and of PhP(CN), with C N -, and it may best be prepared by nucleophilic degradation of (PhP), with ammonium or phosphonium cyanides. With sulfur it yields phenyl cyanodithiophosphinates 4, by alkylation alkyl(pheny1)cyanophosphanes 6 and by hydrolysis of the latter alkyl(pheny1)phosphine oxides 7. -The molecular structure of [Ph,PNPPh,]PhPCN (3c) as determined by X-ray analysis shows an almost planar anion with a 102" C P C angle. A long P C and short CN bond in the PCN group make PhPCN-appear as "cyanide complex of phenylphosphinidene".

Phosphaalkenes 1 react as nucleophiles and are converted by chalcogens into the Pv compounds 2 (Y=O, s, Se)."] Thus, reaction of l a (R' = C,H2tBu3, R2 = Ph, R3=SiMe,) with ozone at -78°C affords a stable methyleneoxophosphorane 2a (Y = 0);l2' with a n excess of ozone, secondary reactions take place)'' most likely with cleavage of the P-C bond.I3]We have now found that the electron-rich phosphaalkene lbI4] takes up two equivalents of oxygen smoothly and selectively upon reaction with ozone at room temperature, leading directly to formation of 3b. 2b (Y=O) is not observed as a n intermediate, since a part of l b remains unchanged upon reaction with less ozone, and more ozone does not lead to secondary reactions.In the I3C-NMR spectrum (CD,CN) of 3b1'] the downfield shift of the sp2 C-atom observed for l b (6=200, Jpc = 67 Hzl4]) is essentially retained (6 = 180, Jpc = 91 Hz). This is not consistent with the epoxide 4b (oxaphosphirane oxide), and rather suggests formation of the zwitterionic amidiniophosphinate 3b.I6I The thiaphosphirane sulfides 5 corresponding to 4b can be synthesized from methylenethioxophosphoranes 2 (Y = S) by (reversible) uptake of sulfur.II1 3b is also accessible from dimethyl phenylphosphonite and tetramethylurea d i~h l o r i d e .~~~The tetrakis(dimethylamino)-2-phosphaallyl cation 6[*] is smoothly converted into the colorless dioxide 7, not [' I Prof.

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AbstractLithiumorganyls RLi (R = Me, Bu, Ph) add to (PhP)5 in successive degradation and disproportionation equilibria depending on the ratio of the reactants. At -70 °C (R = Me) disproportionation is blocked and (PhP)4R- and (PhP)3R- can be detected. With excess RLi m onophosphides PhPR- are formed. CpNa with the help of a crown ether degrades (PhP)5 or substitutes cyanide from PhPCN- to give an equilibrium mixture of (PhP)nCp- anions, which stabilize by proton shifts: In case of n = 1 and 2 a shift from the Cp unit to the terminal phosphorus results in the formation of the phenylphosphino- and diphenyldiphosphino-cyclopentadienide anion, in case of n = 3 two proton shifts within the Cp unit result in a cyclopenteno-l,2,3-triphospholene allylic anion.

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