FERROCENYLBIS(YLENE) PHOSPHORANES

The ferrocenylbis(methylene)phosphorane Fc-P(=CTms(2))(2) (1) (Fc=-C5H 4FeC5H5) can be synthesized starting from ferrocenyldichlorophosphane FcPCl(2) or ferrocenyldilithiophosphane FcPLi(2). The X-ray structure of (1) shows some unusual structural features, which indicate consider able electronic interaction of the ferrocenyl group and the a sigma(3) lambda(5)-phosphorane unit. As a consequence of this interaction, the rotational barrier of the methylene bonds is extraordinary low. There fore, in contrast to other bis(methylene)phosphoranes, the endo-and ex o-Tms groups are indistinguishable on the NMR time scale even at -100 degrees C. The analogous ferrocenylbis(imino)phosphorane Fc-P(=NTms)(2 ) (9), can only be isolated in its dimeric form. The conditions, which are necessary for the formation of (9) from the corresponding azidoph osphane Fc-P(N-3)NTms(2) under elimination of nitrogen lead to a self addition reaction of (9). The elimination of nitrogen is facilitated b y polar solvents, and electrophilic reagents. (C) 1997 Elsevier Scienc e S.A.