Tuning the Dissociation of the Fe鈥揚Ph2(OR) Bond in Chiral-at-Metal Complexes [CpFe(Prophos)PPh2(OR)]PF6 (R = Me, Et, iPr, tBu). The Preparative Trick of

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• 作者：Henri Brunner ; Takaki Kurosawa ; Manfred Muschiol ; Takashi Tsuno ; G谩bor Bal谩zs ; Michael Bodensteiner
• 刊名：Organometallics
• 出版年：2013
• 出版时间：September 9, 2013
• 年：2013
• 卷：32
• 期：17
• 页码：4904-4911
• 全文大小：385K
• 年卷期：v.32,no.17(September 9, 2013)
• ISSN：1520-6041

文摘

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 N₂ through the solution speeded up the slow substitution reactions by removing the acetonitrile formed in the rate-determining cleavage of the Fe鈥揘CMe 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鈥揚Ph₂(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 掳C.