[(Cp*)(dppe)Fe(III)-]+ Units Bridged through 1,3-Diethynylbenzene and 1,3,5-Triethynylbenzene Spacers: Ferromagnetic Metal-Metal Exchange Interaction
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- 作者：Tania Weyland ; Karine Costuas ; Alain Mari ; Jean-Franç ; ois Halet ; and Claude Lapinte
- 刊名：Organometallics
- 出版年：1998
- 出版时间：December 7, 1998
- 年：1998
- 卷：17
- 期：25
- 页码：5569 - 5579
- 全文大小：205K
- 年卷期：v.17,no.25(December 7, 1998)
- ISSN：1520-6041
文摘
The bi- and trinuclear iron(III) complexes [1,3-{Cp*(dppe)Fe(C
C-)}2(C6H4)][PF6]2 (22+)and [1,3,5-{Cp*(dppe)Fe(CC-)}3(C6H3)] [PF6] (33+) were prepared by oxidation of [1,3-{Cp*(dppe)Fe(CC-)}2(C6H4)] or [1,3,5-{Cp*(dppe)Fe(CC-)}3(C6H3)] with 2 or 3 equiv of[(C5H5)2Fe][PF6], respectively. Complexes 22+ and 33+ were isolated as thermally and airstable blue microcrystalline solids in 95 and 80% yield, respectively. These paramagneticcompounds were characterized by cyclic voltammetry, IR, UV-vis, 1H NMR, Mössbauer,and ESR spectroscopies. The three organoiron groups of 33+ are not located on the sameside of the molecule, and its two faces are therefore magnetically nonequivalent. The 1HNMR isotropic shifts are expected to be essentially contact shifts and the zfs (zero fieldsplitting) parameter D is expected to be small for 22+ and 33+ since the Curie law is accuratelyobeyed for the proton resonances of the 
-bound Cp* ligand. ESR spectra of the bi- andtriradicals showed broad and unresolved signals at g = 2.10 (22+, 
Hpp = 550 G) and 2.13(33+, Hpp = 170 G) in addition to signals at g = 4.55 and 4.46, respectively due to ms =2 transition. The ms = 3 transition was observed at g = 7.97 in the spectrum of 33+. Thetemperature dependence of molar susceptibility obtained by SQUID measurements onmicrocrystalline samples suggested that the ferromagnetic interaction produces a tripletground state in biradical 22+ (2J = 130.6 ± 0.2 cm-1) and a quartet ground state for triradical33+. The two doublet states lie above the quartet by 18.7 ± 0.2 and 28.8 ± 0.2 cm-1. Theseresults constitute the first examples of magnetic exchange interactions in a three-spinorganometallic system with a triangular topology and the ferromagnetic coupling occurs atnanoscale distances between the metal spin carriers. The geometries of 22+ and 33+ wereoptimized using DFT calculations. High spin species were computed to be energeticallyfavored with the spin density mainly localized on the iron centers supporting the experimentalresults.
C-)}2(C6H4)][PF6]2 (22+)and [1,3,5-{Cp*(dppe)Fe(CC-)}3(C6H3)] [PF6] (33+) were prepared by oxidation of [1,3-{Cp*(dppe)Fe(CC-)}2(C6H4)] or [1,3,5-{Cp*(dppe)Fe(CC-)}3(C6H3)] with 2 or 3 equiv of[(C5H5)2Fe][PF6], respectively. Complexes 22+ and 33+ were isolated as thermally and airstable blue microcrystalline solids in 95 and 80% yield, respectively. These paramagneticcompounds were characterized by cyclic voltammetry, IR, UV-vis, 1H NMR, Mössbauer,and ESR spectroscopies. The three organoiron groups of 33+ are not located on the sameside of the molecule, and its two faces are therefore magnetically nonequivalent. The 1HNMR isotropic shifts are expected to be essentially contact shifts and the zfs (zero fieldsplitting) parameter D is expected to be small for 22+ and 33+ since the Curie law is accuratelyobeyed for the proton resonances of the -bound Cp* ligand. ESR spectra of the bi- andtriradicals showed broad and unresolved signals at g = 2.10 (22+, Hpp = 550 G) and 2.13(33+, Hpp = 170 G) in addition to signals at g = 4.55 and 4.46, respectively due to ms =2 transition. The ms = 3 transition was observed at g = 7.97 in the spectrum of 33+. Thetemperature dependence of molar susceptibility obtained by SQUID measurements onmicrocrystalline samples suggested that the ferromagnetic interaction produces a tripletground state in biradical 22+ (2J = 130.6 ± 0.2 cm-1) and a quartet ground state for triradical33+. The two doublet states lie above the quartet by 18.7 ± 0.2 and 28.8 ± 0.2 cm-1. Theseresults constitute the first examples of magnetic exchange interactions in a three-spinorganometallic system with a triangular topology and the ferromagnetic coupling occurs atnanoscale distances between the metal spin carriers. The geometries of 22+ and 33+ wereoptimized using DFT calculations. High spin species were computed to be energeticallyfavored with the spin density mainly localized on the iron centers supporting the experimentalresults.