Aqueous organometallic chemistry. Structure and dynamics in the formation of ({eta}{sup 5}-pentamethylcyclopentadienyl)rhodium aqua complexes as a function of pH
- Israel Inst. of Technology, Haifa (Israel)
- Lawrence Berkeley Lab., CA (United States); Univ. of California, Berkeley, CA (United States)
- Univ. of California, Davis, CA (United States)
The structures of the ({eta}{sup 5}-pentamethylcyclopentadienyl)rhodium aqua complexes, as a function of pH, were studied by {sup 1}H, {sup 13}C, {sup 17}O, and 2D NOESY NMR spectroscopic techniques as well as by FAB mass spectrometry and potentiometric titration. The starting complex for our NMR experiments, [Cp{sup *}Rh(H{sub 2}O){sub 3}](OTf){sub 2}, 1, was structurally characterized by single-crystal X-ray crystallography. Both {sup 1}H and {sup 13}C NMR titration experiments of the starting complex, 1, were performed by dissolving 1 in H{sub 2}O (D{sub 2}O) and obtaining spectra from pH 2-14. From pH 2-5 only one Cp{sup *} signal ({sup 1}H NMR, 1.57 ppm; {sup 13}C NMR, 5.78 ppm) was observed, which was attributed to 1. As the pH of the solution with 1 was increased from 5 to 7, a dynamic and rapid equilibrium was observed to provide putative [Cp{sup *}Rh({mu}-OH)(H{sub 2}O)]{sub 2}(OTf){sub 2}, 2, and [(Cp{sup *}Rh){sub 2}({mu}-OH){sub 3}](OTf/OH), 3; unfortunately, only one {sup 1}H or {sup 13}C NMR signal for Cp{sup *}Rh at 1.50 (Cp{sup *}) or 5.41 ppm (C-CH{sub 3}), respectively, was found for the latter two species, with broadening of the signals at pH 5.5-6, indicating that conversion from putative 2 to 3 was very fast on the NMR time scale. As the pH was further increased from 7 to 10, only the {sup 1}H or {sup 13}C NMR signal for 3 was observed at 1.50 or 5.41 ppm, respectively. 12 refs., 5 figs., 3 tabs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 70371
- Journal Information:
- Organometallics, Journal Name: Organometallics Journal Issue: 6 Vol. 14; ISSN 0276-7333; ISSN ORGND7
- Country of Publication:
- United States
- Language:
- English
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