- Synthesis, characterisation and molecular structure of [Rh(COE)2(acac)] (COE = cyclooctene, η2-C8H14), an important starting material for the preparation of rhodium catalyst precursors
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The compound [Rh(COE)2(acac)] (1) is a catalyst precursor in its own right, and a starting material for the preparation of other catalyst precursors for use in a variety of reactions such as hydroboration, diboration and the addition of arylbor
- Burke, Jacquelyn M.,Benjamin Coapes,Goeta, Andrés E.,Howard, Judith A.K.,Marder, Todd B.,Robins, Edward G.,Westcott, Stephen A.
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- Convenient synthetic access to fluorescent rhodacyclopentadienes via ligand exchange reactions
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We have previously reported the formation of fluorescent 2,5-bis(arylethynyl)rhodacyclopentadienes from the reaction of [Rh(κ2-O,O-acac)(PMe3)2] (acac = acetylacetonato) with α,ω-bis(arylbutadiynyl)alkanes. However, a second isomer series, namely phosphorescent rhodium biphenyl complexes, was also obtained from the same reaction mixture, which made purification of the 2,5-bis(arylethynyl)rhodacyclopentadienes challenging and led to low isolated yields. Herein, we describe a synthetic protocol to access the desired fluorescent rhodium complexes by reaction of [Rh(κ2-O,O-acac)(P(p-tolyl3)2)] with α,ω-bis(arylbutadiynyl)alkanes, which gives exclusively 2,5-bis(arylethynyl)rhodacyclopentadienes, and subsequent phosphine ligand exchange. The rhodacyclopentadienes bearing P(p-tolyl3) ligands have been investigated and compared to their PMe3 analogs with regard to their photophysical properties, showing that the aromatic phosphine ligands enhance non-radiative decay from the singlet excited state S1, while no phosphorescence from T1 is observed despite the presence of the heavy rhodium atom. One of the P(p-tolyl3) ligands can also be exchanged for an N-heterocyclic carbene (NHC), leading to unsymmetrically coordinated rhodacyclopentadienes.
- Sieck, Carolin,Sieh, Daniel,Sapotta, Meike,Haehnel, Martin,Edkins, Katharina,Lorbach, Andreas,Steffen, Andreas,Marder, Todd B.
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p. 184 - 192
(2017/09/12)
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- Efficient synthesis of the cyclometalated complex fac-[Rh(ppy)3] (ppy = 2-phenylpyridinato)
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A new convenient high-yield synthesis of the tris-cyclometalated complexes fac-[Rh(ppy)3] (4; ppy = 2-phenylpyridinato) was developed. Complex 4 was prepared in a kind of one-pot synthesis starting from in situ prepared [Rh(acac)(coe)2] (2) which was heated in refluxing 2-phenylpyridine for a short time. After purification by filtration over alumina, compound 4 was obtained in yields of 65%. Also [Rh(acac)(ppy)2] (3) was prepared in a similar manner by oxidative addition of Hppy in refluxing toluene in high yields. In contrast to previous findings with the analogous iridium compounds, there was not any hint at the formation of the isomer mer-[Rh(ppy)3] using similar reaction conditions as applied for iridium. Furthermore the compound [{Rh(μ-Cl)(ppy)2}2] (5) was prepared from [{Rh(μ-Cl)(coe)2}2] (1) and Hppy in refluxing toluene in nearly quantitative yield.
- B?ttcher, Hans-Christian,Graf, Marion,Sünkel, Karlheinz,Krüger, Hartmut
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p. 523 - 525
(2011/05/28)
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- Synthesis of the tris-cyclometalated complex fac-[Rh(ptpy)3] and X-ray crystal structure of [Rh(acac)(ptpy)2]
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New convenient syntheses of the cyclometalated complexes [Rh(acac)(ptpy)2] (3, ptpy = 2-(p-tolyl)pyridinato) and fac-[Rh(ptpy)3] (4) are described. The compounds were prepared in a kind of one-pot synthesis starting from in situ prepared [Rh(acac)(coe) 2] (2) (coe = cis-cyclooctene) followed by reaction with Hptpy in refluxing toluene. Under these conditions oxidative addition occurred and the new complex 3 was obtained in good yields. Compound 4 was prepared in good yields by reaction of 3 with Hptpy in excess. The complex 3 crystallized from dichloromethane/iso-hexane in the space group P - 1 and its molecular structure was confirmed by a single-crystal X-ray diffraction study. The absorption and emission spectra exhibit the new compounds as red-emitting phosphorescent complexes.
- B?ttcher, Hans-Christian,Graf, Marion,Sünkel, Karlheinz,Salert, Beatrice,Krüger, Hartmut
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p. 377 - 379
(2011/03/21)
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