(1,3-Dimethyluracil-5-yl)mercury(II): Preparative, Structural, and NMR Spectroscopic Studies of an Analog of CH(3)Hg(II)

The solution behavior of (1,3-DimeU-C5)Hg(CH(3)COO) (1a) (1,3-DimeU = 1,3-dimethyluracil) with regard to acetate replacement by anions X (Cl(-), Br(-), I(-), NO(3)(-), SCN(-), CN(-)) and by other model nucleobases (1-methylcytosine, 1-MeC, 1-methyluracil, 1-MeUH, 1-methylthymine, 1-MeTH, 9-ethylguanine, 9-EtGH, and 2-thiouracil, 2-ThioUH) has been studied, primarily by means of (1)H and (199)Hg NMR spectroscopy. Moreover, the bis(1,3-DimeU-C5) complex of Hg has been crystallized and studied by X-ray crystallography. 7a: orthorhombic system, space group Fdd2, a = 14.185(4) ?, b = 25.275(7) ?, c = 7.924(2) ?, V = 2840(2) ?(3), Z = 8. The acetato ligand of 1a is readily displaced by anions X, frequently followed by disproportionation reactions leading to HgX(2) and 7a. The donor atom X trans to C(5) has an effect on (3)J coupling between (199)Hg and H(6) of the 1,3-DimeU ligand according to NO(3)(-) > OAc(-) > Cl(-) approximately Br(-) > I(-) > SCN(-) > CN(-) > 1,3-DimeU-C5 with extremes being 222 (X = NO(3)(-)) and 107 Hz (7a). In the presence of excess metal ions (Ag(+), Hg(2+)), 1a forms hetero- and homonuclear derivatives with the second metal ion probably sitting at O(4). The mixed nucleobase 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 (1)H time scale. In several cases, e.g. 2a, 3a, 4a, and 5a, formation of dinuclear Hg or heteronuclear Ag and Pt derivatives has been established by multinuclear NMR spectroscopy.