Formation of a Hexacarbonyl Diiron Complex Having a Naphthalene-1,8-bis(phenylphosphido) Bridge and the Electrochemical Behavior of Its Derivatives

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• 作者：Yuichi Teramoto ; Kazuyuki Kubo ; Shoko Kume ; Tsutomu Mizuta
• 刊名：Organometallics
• 出版年：2013
• 出版时间：December 9, 2013
• 年：2013
• 卷：32
• 期：23
• 页码：7014-7024
• 全文大小：473K
• 年卷期：v.32,no.23(December 9, 2013)
• ISSN：1520-6041

文摘

The P鈥揚 bond of the cis-1 ligand in (渭-cis-1)[Fe(CO)₄]₂ (cis-1 = naphthalene-1,8-diphenyldiphosphine) was cleaved by the two iron centers after CO dissociation from the iron centers, although the P鈥揚 bond of cis-1 was stereochemically stabilized with a robust naphthalene group, unlike the usual diphosphines, which lack such support. The resulting (渭-nabip)[Fe(CO)₃]₂ (3; nabip = naphthalene-1,8-bis(phenylphosphido)) had the diiron core linked by the bisphosphido bridge. Since the trans isomer (渭-trans-1)[Fe(CO)₄]₂ was stable under ambient conditions, the cis disposition of the two Fe(CO)₄ fragments was responsible for the cleavage of the P鈥揚 bond. The one or two terminal CO ligands of 3 can be replaced by MeCN and a range of phosphine ligands: i.e., PMe₃, PPh₃, cis-1, and trans-1. Interestingly, it was found that the diphosphine cis-1 could coordinate the iron center in an unusual 魏² fashion to form a three-membered ring, which was confirmed by NMR spectra as well as X-ray analysis. These diiron complexes can be protonated with the strong acid TfOH in CH₂Cl₂ to form cationic complexes having a 渭-H bridge between the two iron centers. The parent hexacarbonyl complex 3 could act as a proton reduction catalyst at 鈭?.0 V in the presence of TsOH as the proton source in CH₂Cl₂. When protonated complexes having MeCN or phosphine ligands were used, the proton reduction potentials catalyzed by these complexes were shifted to a more positive range of around 鈭?.77 to 鈭?.37 V, depending on the terminal ligand.