ZUR REAKTION VON METALL-KOORDINIERTEM KOHLENMONOXID MIT YLIDEN. VIII. TRIMETHYL(METHYLEN)PHOSPHORAN-KATALYSIERTE ISOMERISIERUNG EINES EISENACYL-PHOSPHORYLIDS. UEBERTRAGUNG DER Cp(CO)2FeC(O)-EINHEIT ZWISCHEN YLIDISCHEN ZENTREN

Article abstract of DOI:10.1016/S0022-328X(00)85729-0

The addition of MeI to the ironacyl phosphorusylide Cp(CO)2FeC(O)CH=PMe3 (I) gives the phosphonium salt I (II), which can be dehydrohalogenated with Me3P=CH2 to the corresponding ylide Cp(CO)2FeC(O)(Me)C=PMe3 (III).III is thermally stable in the pure state, but rearranges irreversibly with the addition of a trace of Me3P=CH2 to the thermodynamically favored isomer Cp(CO)2FeC(O)HC=PEtMe2 (IV).A plausible mechanism for the rearrangement is established, involving the intermolecular transfer of the Cp(CO)2FeC(O)-group between the tautomeric ylides Me3P=CHMe and EtMe2P=CH2.It is proved by the simple reaction of Cp(CO)2FeC(O)(Me)C=PEt3 (V) with Me3P=CH2 to give quantitatively I and Et3P=CHMe.The first ylide rearrangement involving the shift of a transition metal group is mainly induced by the better electronic stabilization of the ylidic function, when the Cp(CO)2FeC(O) moiety is combined with a hydrogen atom.