Synthesis, Characterization, and Electrochemistry of a Series of Iron(II) Complexes Containing Self-Assembled 1,5-Diaza-3,7-diphosphabicyclo[3.3.1]nonane Ligands

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• 作者：Andrew D. Burrows ; Ross W. Harrington ; Andrew S. Kirk ; Mary F. Mahon ; Frank Marken ; John E. Warren ; Michael K. Whittlesey
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：October 19, 2009
• 年：2009
• 卷：48
• 期：20
• 页码：9924-9935
• 全文大小：1053K
• 年卷期：v.48,no.20(October 19, 2009)
• ISSN：1520-510X

文摘

The reaction between PPh(CH₂OH)₂, iron(II) sulfate, ammonium sulfate, and formaldehyde in aqueous solution gives the iron(II) complex [Fe(κ²-O₂SO₂)L₂] (1), where L is the bidentate phosphine ligand 3,7-diphenyl-1,5-diaza-3,7-diphosphabicyclo[3.3.1]nonane. During the course of the reaction, the ligand L self-assembles on the metal center. The reaction between PPh(CH₂OH)₂, iron(II) chloride, ammonium chloride, and formaldehyde under similar conditions gives cis-[FeCl₂L₂] (cis-2). The complex cis-2 is converted into trans-2 in Et₂O, whereas in water it is converted into cis-[Fe(OH₂)₂L₂]²⁺, though both of these interconversions are reversible. The chloro ligands in cis-2 are readily displaced by reaction with thiocyanate, azide, and carbonate to give cis- and trans-[Fe(NCS)₂L₂] (cis- and trans-3), cis- and trans-[Fe(N₃)₂L₂] (cis- and trans-4), and [Fe(κ²-O₂CO)L₂] (5), respectively. The complex cis-2 reacts with CO in water to give trans-[FeCl(CO)L₂]Cl (trans-6), whereas trans-2 reacts with CO in diethyl ether to give cis-[FeCl(CO)L₂]Cl (cis-6), though cis-6 isomerizes in water to form trans-6. The reaction of cis-2 with sodium borohydride gives the hydride chloride complex trans-[FeCl(H)L₂] (7). Electrochemical studies have been undertaken on complexes 1, cis-2, and 7. These reveal reversible oxidations for cis-2 and 7, with the latter giving rise to an unusual 17-electron iron(III) hydride chloride complex. Crystal structures have been obtained for 1, trans-2, trans-3, 5, and 7.