BIOORGANOMETALLIC CHEMISTRY .2. SYNTHESIS AND STRUCTURAL STUDIES OF THE REACTIONS OF A NUCLEOBASE, 1-METHYLCYTOSINE, WITH A (ETA-5-PENTAMETHYLCYCLOPENTADIENYL)RHODIUM AQUA COMPLEX

The reactions of a nucleobase, 1-methylcytosine (MC), with a Cp*Rh aqua complex, [(eta5-Cp*)-Rh(H2O)2(OTf)2]x (2), provided two different complexes depending on the solvent media. Complex 3, [(eta5-Cp*)-Rh(eta1(N3)-MC)(eta2(O2,N3)-MC)](OTf)2, was formed when acetone was used as the solvent; however, when complex 3 was recrystallized from water (pH 5. 1) or when water was used as the reaction solvent, complex 4, trans-[(eta5-Cp*)Rh(eta1(N3)-MC)(mu-OH)]2(OTf)2, was isolated as a crystalline solid. The structures of 3 and 4 were verified by H-1 NMR, FAB/MS, elemental analysis, and single-crystal X-ray analysis. The structure of complex 3 showed one MC ligand bound via N3 and the other chelated via N3 and C = O2 (Rh-O2 = 2.251(6) angstrom). Inspection of several bond lengths of complex 4 indicates extensive intramolecular hydrogen bonding of the mu-OH groups with the exocyclic NH2 (HO --- HNH = 1.93(1) angstrom) and the 2-C = O group (OH --- 0 = C = 1.96(1) angstrom).