Kinetically and Thermodynamically Controlled Formation of Homo- and Heterobinuclear Platinum(II) and Palladium(II) Complexes Supported by Bidentate Triazolopyrimidine Ligands.
The formation of the mononuclear Pt(II) compound cis-[Pt(NH(3))(2)(Hmtpo-N(3))(2)](NO(3))(2).2H(2)O (1) (Hmtpo = 4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine) upon reaction of Hmtpo with cisplatin is reported. Subsequent reactions of 1 with Pd(II) electrophiles of the type [Pd(am)(2)(H(2)O)(2)](NO(3))(2) ((am)(2) = en, bpy) in neutral aqueous media afford heterobinuclear complexes of formula [(NH(3))(2)Pt(&mgr;-mtpo-N(3),N(4))(2)Pd(am)(2)](NO(3))(2), where (am)(2) = bpy (2) and en (3). On the other hand, reaction of 1 with the platinum electrophile [Pt(bpy)(H(2)O)(2)](2+) yields the binuclear compound [(mtpo-N(3))(NH(3))(2)Pt(&mgr;-mtpo-N(3),N(4))Pt(bpy)(OH)](NO(3)).6H(2)O (4). The compounds have been structurally characterized by 1-D and 2-D (1)H NMR spectroscopy and X-ray crystallography (1, 2, and 4). Compound 1 crystallizes in the triclinic space group P&onemacr; with unit cell dimensions a = 7.859(1) Å, b = 11.811(2), c = 12.986(2) Å, alpha = 73.69(1) degrees, beta = 84.53(1) degrees, gamma = 85.80(1) degrees, and Z = 2. Compound 2 crystallizes in the monoclinic space group P2(1)/c with unit cell dimensions a = 13.752(1) Å, b = 12.5658(8) Å, c = 19.215(1) Å, beta = 118.08(1) degrees, and Z = 4. Compound 4 crystallizes in the triclinic space group P&onemacr; with unit cell dimensions a = 10.282(2) Å, b = 14.133(3) Å, c = 14.794(3) Å, alpha = 110.63(3) degrees, beta = 97.83(3) degrees, gamma = 108.48(3) degrees, and Z = 2. The structure of 1 consists of mononuclear cis-[Pt(NH(3))(2)(Hmtpo-N(3))(2)](2+) cations, in which the Hmtpo ligands are coordinated through N(3) in a monodentate fashion. In compound 2, two mtpo moieties bridge the metal centers through N(3) and N(4), giving rise to a Pt-Pd separation of 3.083(1) Å. On the other hand, only one bridging mtpo moiety is present in 4, which accounts for a lengthening in the M-M separation to 3.337(1) Å. The environment around the metal centers consists of four nitrogens, except for one Pt nucleus in compound 4, which presents a rare example of a terminal OH group. The (1)H NMR studies show clearly that these structures are retained in solution. Finally, a bidentate bridging mode through N(1)/N(3) is postulated for the species generated in solution by the reaction of 1 with the electrophile [Pt(NH(3))(2)(H(2)O)(2)](2+), which may lead to tetranuclear or polymeric species.
Navarro
Jorge A. R.
JA
Departamento de Química Inorgánica, Universidad de Granada, 18071 Granada, Spain.
Romero
M. Angustias
MA
Salas
Juan M.
JM
Quirós
Miguel
M