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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

Lookup NU author(s): Dr Ross Harrington


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The reaction between PPh(CH2OH)(2), iron(II) sulfate, ammonium sulfate, and formaldehyde in aqueous solution gives the iron(II) complex [Fe(kappa(2)-O2SO2)L-2] (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)(2)L-2](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)(2)L-2] (cis- and trans-3), cis- and trans-[Fe(N-3)(2)L-2] (cis- and trans-4), and [Fe(kappa(2)-O2CO)L-2] (5), respectively. The complex cis-2 reacts with CO in water to give trans-[FeCl(CO)L-2]Cl (trans-6), whereas trans-2 reacts with CO in diethyl ether to give cis-[FeCl(CO)L-2]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)L-2] (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.

Publication metadata

Author(s): Burrows AD, Harrington RW, Kirk AS, Mahon MF, Marken F, Warren JE, Whittlesey MK

Publication type: Article

Publication status: Published

Journal: Inorganic Chemistry

Year: 2009

Volume: 48

Issue: 20

Pages: 9924-9935

ISSN (print): 0020-1669

ISSN (electronic): 1520-510X

Publisher: American Chemical Society


DOI: 10.1021/ic900874f


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