Zusammenfassung
The compounds (R-Fe,R-C)-/(S-Fe,R-C)-[CpFe-(Prophos)PPh(OMe)(2)]PF6 and (R-Fe,R-C)-/(S-Fe,R-C)-[CpFe-(Prophos)PPh2(OR)]PF6 (R = Me, Et, iPr, tBu) were synthesized, starting from (R-Fe,R-C)-/(S-Fe,R-C)-[CpFe(Prophos)NCMe]PF6, and characterized, including X-ray analyses. Bubbling a stream of N-2 through the solution speeded up the slow substitution reactions by removing the acetonitrile formed in ...
Zusammenfassung
The compounds (R-Fe,R-C)-/(S-Fe,R-C)-[CpFe-(Prophos)PPh(OMe)(2)]PF6 and (R-Fe,R-C)-/(S-Fe,R-C)-[CpFe-(Prophos)PPh2(OR)]PF6 (R = Me, Et, iPr, tBu) were synthesized, starting from (R-Fe,R-C)-/(S-Fe,R-C)-[CpFe(Prophos)NCMe]PF6, and characterized, including X-ray analyses. Bubbling a stream of N-2 through the solution speeded up the slow substitution reactions by removing the acetonitrile formed in the rate-determining cleavage of the Fe NCMe bond. Due to their acceptor ligands P(OMe)(3) and PPh(OMe)(2) the complexes [CpFe(Prophos)P(OMe)(3)]PF6 and [CpFe(Prophos)PPh(OMe)(2)]PF6 are configurationally stable at the metal atom. In contrast, [CpFe(Prophos)PPh3]PF6 does not form, due to the large cone angle of the ligand PPh3. Ideally, the electronic and steric effects of the ligands PPh2(OR) (R = Me, Et, iPr, tBu) are such that they tend to dissociate from the congested complexes (R-Fe,R-C)- and (S-Fe,R-C)-[CpFe(Prophos)PPh2(OR))]PF6. In the series (R-Fe,R-C)- and (S-Fe,R-C)-[CpFe(Prophos)PPh2(OR)]PF6, (R = Me, Et, iPr, tBu) electron donation and the cone angle of the ligands increase. Thus, the rates of the ligand exchange with P(OMe)(3) increased, initiated by the slow dissociation of the Fe-PPh2(OR) bond. For the R-Fe,R-C/S-Fe,R-C diastereomers of [CpFe(Prophos)PPh2(OR)]PF6 the half-lives of the first-order reactions were 125/350 h (R = Me), 75/275 h (R = Et), and 12/34 h (R = iPr) in CDCl3 at 60 degrees C.
Altmetric