| Abstract
| - The new complexes trans-[a2Pt(Hpymo-N1)2]X2 (a = NH3, X= NO3 (1a); a = CH3NH2, X= NO3(1b); a =CH3NH2, X= ClO4 (1c); Hpymo = 2-hydroxypyrimidine) have been prepared by reaction of trans-[a2Pt(H2O)2]X2 with 2-hydroxypyrimidine at 80 °C in water. Complex 1c cocrystallizes in water with 2-aminopyrimidine(ampym) through formation of complementary pairs of hydrogen bonds to give the supramolecular hexagon {trans-[(CH3NH2)2Pt(pymo-N1)(Hpymo-N1)]·Hampym}2(ClO4)4 (2). Molecular recognition of ampym by 1c is responsiblefor a conformational change of the two hydroxypyrimidine ligands in 1c from anti (1c) to syn and in addition fora proton transfer from a Hpymo residue to ampym against 1.5 units of pKa gradient. 1H NMR concentration-dependent studies as well as NOE experiments in dmso-d6 and dmf-d7 show that 2 dissociates in solution. Compound1a reacts in NH3:H2O (1:3) with AgI to give the polymeric species {trans-[(NH3)2Pt(μ-pymo-N1,N3)2Ag(H2O)]NO3}n (3). In contrast to 2, in the polymeric structure the trans-[(NH3)2Pt(pymo)2] entities adopt an anticonformation. Nevertheless, the [(H2O)Ag(pymo)2] residues present a syn conformation that leads to a meander-like global structure. Compounds 1b, 1c, 2, and 3 have been studied by X-ray crystallography: (1b) triclinicspace group, P1̄, a = 9.300(2) Å, b = 10.483(2) Å, c = 11.050(2) Å, α = 68.21(3)°, β = 75.47(3)°, γ =73.83(3)°, Z = 2, R1 = 0.025, and wR2 = 0.062; (1c) triclinic space group, P1̄, a = 5.692(1) Å, b = 7.758(2)Å, c = 11.236(2) Å, α = 93.12(3)°, β = 92.86(3)°, γ = 102.58(3)°, Z = 2, R1 = 0.048, and wR2 = 0.119; (2)triclinic space group, P1̄, a = 8.355(2) Å, b = 11.221(2) Å, c = 13.004(3) Å, α = 86.76(3)°, β = 78.62(3)°, γ= 77.96(3)°, Z = 2, R1 = 0.033, and wR2 = 0.080; (3) monoclinic space group, C2/c, a = 5.345(1) Å, b =23.998(5) Å, c = 12.474(2) Å, β = 102.27(3)°, Z = 8, R1 = 0.041, and wR2 = 0.093.
- Compounds of type trans-[a2Pt(2-hydroxypyrimidine)2]X2 (1) (a = NH3, CH3NH2; X = NO3, ClO4) have been used as building blocks for more complex structures. On one hand, the interaction of 1 with 2-aminopyrimidine through complementary pairs of H bonds leads to the molecular hexagon 2. On the other hand, covalent bonding of AgI generates the polymeric structure 3.
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