|Title||Bioorganometallic chemistry: Part 12. Reaction of [Cp*Rh(H2O)3](OTf)2 with nicotinamide adenine dinucleotide in water: synthesis, structure, and a pH-dependent 1H-NMR and voltammetric study of the cyclic trimer product, [Cp*Rh([mu]-[eta]1(N1):[eta]2(N6,N7|
|Publication Type||Journal Article|
|Year of Publication||1999|
|Authors||Ogo, Seiji, Olivier Buriez, John B. Kerr, and Richard H. Fish|
|Secondary Title||Journal of Organometallic Chemistry|
|Keywords||1h-nmr and cv analysis, nicotinamide adenine dinucleotide, organorhodium-nad complex|
The reaction of [Cp*Rh(H2O)3](OTf)2 (1) with nicotine adenine dinucleotide (NAD+, 2), an important co-factor in enzymatic reactions, was studied utilizing 1H-NMR spectroscopy, electrospray ionization mass spectroscopy (ESI/MS), cyclic voltammetry (CV), and isolation techniques, as a function of pH. The product was formulated from the above-mentioned spectroscopic data as the well-known Cp*Rh cyclic trimer structure, [Cp*Rh([mu]-[eta]1(N1):[eta]2(N6,N7)-9-(5'-ribose pyrophosphate-5''-ribose-1''-nicotinamide)adeninato]3(OTf)3, 3, which forms via a self-assembly mechanism as the pH is increased from 3 to 6 (1H-NMR). We also compared 3 with the putative one reported that formed via reaction with [(Cp*Rh)2([mu]-Cl2)Cl2] and was tentatively assigned the formula, [Cp*Rh(NAD)Cl](Cl). In fact, both Cp*Rh synthons provide the same cyclic trimer product at pH 6, while a presumed mixture of [Cp*Rh(NAD)] and Cp*Rh aqua intermediates (at least eight Cp*Rh 1H-NMR signals are evident) were formed at pH 3.0. A full analysis of the CV data reveals that some Cp*Rh aqua complexes are electroactive at potentials around -1.2 V versus Ag | AgCl, but probably not the cyclic trimer, complex 3. Unfortunately, we were not able to utilize complex 3 in an intramolecular, regioselective reduction reaction, with sodium formate as the hydride source, to provide the corresponding biologically active 1,4-dihydro derivative.
0022-328Xdoi: DOI: 10.1016/S0022-328X(99)00303-4