Bioorganometallic Chemistry. 27. Synthetic, X-ray Crystallographic, and Competitive Binding Studies in the Reactions of Nucleobases, Nucleosides, and Nucleotides with [Cp*Rh(H2O)3
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- 作者：David P. Smith ; Hong Chen ; Seiji Ogo ; Ana I. Elduque ; Miriam Eisenstein ; Marilyn M. Olmstead ; Richard H. Fish
- 刊名：Organometallics
- 出版年：2014
- 出版时间：May 27, 2014
- 年：2014
- 卷：33
- 期：10
- 页码：2389-2404
- 全文大小：720K
- 年卷期：v.33,no.10(May 27, 2014)
- ISSN：1520-6041
文摘
The reactions of the air- and water-stable tris(aqua) complex [Cp*Rh(H2O)3](OTf)2 (1; OTf = trifluoromethanesulfonate) with nucleobases and nucleosides that included 9-methyladenine (9-MA), 9-ethylguanine (9-EG), 9-methylhypoxanthine (9-MH), 9-ethylhypoxanthine (9-EH), 1-methylcytosine (1-MC), 1-methylthymine (1-MT), adenosine (Ado), and guanosine (Guo) provided new bonding modes, all as a function of pH. The 9-MA nucleobase provided a novel cyclic trimer, at pH 6, characteristic for all Ado complexes: [Cp*Rh(渭2-畏1(N1):畏2(N6,N7)-9-MA/Ado)]3(OTf)3. The Cp*Rh(9-EG) and Cp*Rh(Guo) complexes showed N7 and 6-C鈺怬 binding modes in water, [Cp*Rh((畏2(N7,O6)-9-EG/Guo)(OH)](OTf), and no cyclic trimer products, due to a pronounced steric effect of the 2-amino group. This was shown convincingly by the results with 9-MH and 9-EH, which did form cyclic trimers at pH 6.1, [Cp*Rh(渭2-畏1(N1):畏2(N7,O6)-9-MH/9-EH)]3(OTf)3, with a structure similar to that of 9-EG, but with no 2-amino group available. At pH 10.2, the pKa of the 9-MH鈥檚 NH1 hydrogen dictated the structure, providing a 渭-hydroxy dimer, trans-[Cp*Rh(畏1(N1)-9-MH)(渭-OH)]2(OTf)2, while in methanol the same reaction provided a mononuclear complex, [Cp*Rh(畏1(N7)-9-MH)(MeOH)2](OTf)2. The reaction of 1 and 1-MC, at pH 5.4, provided another 渭-hydroxy dimer with intramolecular H bonding of the O and H atoms of the 渭-OH groups (H-acceptor and H-donor, respectively), trans-[Cp*Rh(畏1(N3)-1-MC)(渭-OH)]2(OTf)2, while in acetone, the product was a monomeric complex, [(畏5-Cp*Rh)(畏1(N3)-1-MC)(畏2(O2,N3)-1-MC)](OTf)2. The reaction of 1 and 1-MT at pH 10 showed the initial complex 1 being converted to its equilibrium complex, [(Cp*Rh)2(渭-OH)3]+, and this led to two components being formed. The anionic component was a linear [(畏1(N3)-MT)鈥揜hI鈥?畏1(N3)-MT)]鈥?/b> (12e RhI center) assembly, formed via a presumed reductive elimination of Cp*OH, and included an orthogonal array of two thymine planes. The cationic component was [(Cp*Rh)2(渭-OH)3]+, with its Cp* moiety being 蟺鈥撓€ stacked with thymine rings, as well as the 蟺鈥撓€ interactions of two thymine rings: {[RhI(畏1(N3)-1-MT)2]2[(Cp*Rh)2(渭-OH)3]3}OH. The competitive order of nucleoside reactivity was Ado Guo, while for the nucleotides it was GMP > AMP CMP 鈮?TMP. Finally, we also discuss several examples of the utilization of these unique Cp*Rh鈥揇NA base complexes, as aqueous hosts for molecular recognition of aromatic amino acids and as NMR shift reagents for many organic compounds.