(1,3-DIMETHYLURACIL-5-YL)MERCURY(II) - PREPARATIVE, STRUCTURAL, AND NMR SPECTROSCOPIC STUDIES OF AN ANALOG OF CH3HGII

The solution behavior of (1,3-DimeU-C5)Hg(CH3COO) (1a) (1,3-DimeU = 1, 3-dimethyluracil) with regard to acetate replacement by anions X (Cl-, Br-, I-, NO3-, SCN-, CN-) and by other model nucleobases (1-methylcyt osine, 1-MeC, 1-methyluracil, 1-MeUH, 1-methylthymine, 1-MeTH, 9-ethyl guanine, 9-EtGH, and 2-thiouracil, 2-ThioUH) has been studied, primari ly by means of H-1 and Hg-199 NMR spectroscopy. Moreover, the bis(1,3- DimeU-C5) complex of Hg has been crystallized and studied by X-ray cry stallography. 7a: orthorhombic system, space group Fdd2, a = 14.185(4) Angstrom, b = 25.275(7) Angstrom, c = 7.924(2) Angstrom, V = 2840(2) Angstrom(3), Z = 8. The acetato ligand of 1a is readily displaced by a nions X, frequently followed by disproportionation reactions leading t o HgX(2) and 7a. The donor atom X trans to C(5) has an effect on (3)J coupling between Hg-199 and H(6) of the 1,3-DimeU ligand according to NO3- > OAc- > Cl- similar to Br- > I- > SCN- > CN- > 1,3-DimeU-C5 with extremes being 222 (X = NO3-) and 107 Hz (7a). In the presence of exc ess metal ions (Ag+, Hg2+), 1a forms hetero- and homonuclear derivativ es with the second metal ion probably sitting at O(4). The mixed nucle obase complexes have the second base bound to Hg via N(3) (1-MeU (2a), 1-MeT (3a)), N(4) (1-MeC(-) (4a), 1-MeC (4b)), N(1) (9-EtG (5a)), N(7 ) (9-EtGH (5b)), and N(1), N(7) (9-EtG (5c)), as well as S(2) (2-ThioU (6a)). With the exception of the 9-ethylguanine complexes 5b and 5c, all the other complexes are inert on the H-1 time scale. In several ca ses, e.g. 2a, 3a, 4a, and 5a, formation of dinuclear Hg or heteronucle ar Ag and Pt derivatives has been established by multinuclear NMR spec troscopy.