A cyclic tetranuclear platinum complex of uracil

Abstract

The formation and X-ray structure of a cyclic, tetranuclear Ptll complex of composition [ { P t ( e n ) ( ~H ) ) -~] ( N 0 ~) ~ (uH = uracil monoanion) and its conversion into cyclic, octanuclear derivatives is reported.

Mixed‐Metal (Platinum, Palladium), Mixed‐Pyrimidine (Uracil, Cytosine) Self‐Assembling Metallacalix[n]arenes: Dynamic Combinatorial Chemistry with Nucleobases and Metal Species

“…Unlike related metallacalix[n]arenes with n = 3, [6] 4, [1,2,4] and 6, [7] compound 9 a with n = 8 no longer has the shape of a ring but rather adopts a strongly folded structure ( Figure 11). Compound 9 a crystallizes in space group P4 2 /n and has two crystallographically independent cations.…”

“…[2] There is not only a close conceptual analogy between organic calixarenes and cyclic oligonuclear complexes derived from cis-M II a 2 (a:…”

“…As with the former, the four central metal ions (Pt1, Pt1', Pd1, Pd1') in 7 are in a butterfly arrangement, with deviations of 0.2525(3) (Pt1), 0.2580(3) (Pt1'), À0.2550(3) (Pd1), and À0.2555(3) (Pd1') from the mean plane. The sides of the square range from 5.743(2)-5.917 (2) . The diagonal intermetallic distances are 7.873(3) for Pt···Pt and 8.531(3) for Pd···Pd.…”

“…4 + [1,2] as far as the intermetallic distances and overall arrangement of the pyrimidine bases (1,3-alternate) are concerned. As with the former, the four central metal ions (Pt1, Pt1', Pd1, Pd1') in 7 are in a butterfly arrangement, with deviations of 0.2525(3) (Pt1), 0.2580(3) (Pt1'), À0.2550(3) (Pd1), and À0.2555(3) (Pd1') from the mean plane.…”

“…The complexity of the compounds formed not only results from the possibility of the two different nucleobases in building block 1 engaging in different connectivities with the Pd entities, but also from the potential for the formation of oligomers of different sizes and different conformations; in the case of cyclic tetranuclear Pt 2 Pd 2 species, this can, in principle, lead to the various arrangements (cone, partial cone, 1,2-alternate, 1,3-alternate) known from calix [4]arene chemistry. A further complication arises from the fact that, depending on the mutual orientation of the exocyclic groups of the two nucleobases (O2 and O4 of uracil, O2 and N4 of cytosine), these sites can be engaged in additional chelation of [Pd NH 3 or amine; a 2 : diamine; M: Pt or Pd) and substituted pyrimidine ligands; more importantly, a structural and functional analogy between both types of compounds is evidenced by their capabilities to act as host compounds for guest molecules [3,4] and to permit decoration of the oxygen "rim" by additional metal ions, [5] as well as by the fact that they come in different ring sizes ranging from n = 3 [6] to n = 4 [1][2][3][4] and n = 6. [7] As demonstrated by Navarro and co-workers, there is also the possibility to combine the pyrimidine ligand with another ditopic ligand, such as 4,7-phenanthroline.…”