Syntheses and Structures of C ‐Monoamino‐ P ‐ferriophosphaalkenes[(η 5 ‐C 5 Me 5 )(CO) 2 FeP=CR 1 (NR 2 2 )] (R 1 = Ph, t Bu, 3,4,5‐(MeO) 3 C 6 H 2 ;NR 2 2 = NMe 2 , Piperidino)

Reaction of equimolar amounts of the carbenium iodides [Me 2 N(R)CSMe]I [ 1a : R = Ph; 1b : t Bu; 1c : 3,4,5‐(MeO) 3 C 6 H 2 ], [pip(Ph)CSMe]I ( 1d ) (pip = piperidino), and LiP(SiMe 3 ) 2 · DME afforded phosphaalkenes Me 2 N(R)C=PSiMe 3 ( 2a−c ) and pip(Ph)C=PSiMe 3 ( 2d ). Combination of 2a − d with [(η 5 ‐C 5 Me 5 )(CO) 2 FeCl] led to the formation of [(η 5 ‐C 5 Me 5 )(CO) 2 FeP=C(R)NMe 2 ] [ 3a : R = Ph; 3b : t Bu; 3c : 3,4,5‐(MeO) 3 C 6 H 2 ] and [(η 5 ‐C 5 Me 5 )(CO) 2 FeP=C(Ph)pip] ( 3d ). Compounds 2a−d and 3a−d were characterized by means of spectroscopy (IR, 1 H, 13 C{ 1 H}, 31 P{ 1 H} NMR). The molecular structures of 3a and 3b were determined by X‐ray diffraction analysis. The results of an X‐ray study on [(η 5 ‐C 5 Me 5 )(CO) 2 Fe−P=C(Ph)SiMe 3 ] ( 3g ) for comparison are also included. All experimental observations are rationalized by the assumption that complexes 3a , 3c , and 3d are phosphaalkenes with an inverse π‐electron distribution (P δ−  C δ+ ) and are comparable to [(η 5 ‐C 5 Me 5 )(CO) 2 FeP=C(NMe 2 ) 2 ] ( 3e ), whereas 3b is better regarded as phosphaalkene with a normal polarization (P δ+  C δ− ) of the P=C bond, similar to that given in 3g .