www.elsevier.nl/locate/ica Inorganica Chimica Acta 307 (2000) 125 – 130 Note Palladium phosphine complexes from 8-(thio)-theophylline, 8-(methylthio)-theophylline and 8-(benzylthio)-theophylline Antonio Romerosa a, *, Carlos Lo ´ pez-Magan ˜a a , Mustapha Saoud a , Sonia Man ˜as a , Enrique Colacio b , Jose ´ Sua ´rez-Varela b a Departamento de Quı ´mica Fı ´sica, Bioquı ´mica y Quı ´mica Inorga ´nica, Facultad de Ciencias Experimentales, Uniersidad de Almerı ´a, 04071 Almerı ´a, Spain b Departamento de Quı ´mica Inorga ´nica. Facultad de Ciencias, Uniersidad de Granada, Ada, Fuente Nueas /n, 18071 Granada, Spain Received 1 June 1999; accepted 22 September 1999 Abstract A series of palladium(II) complexes have been synthesized and characterized to examine the coordination chemistry of several 8-thio-purine derivatives: 8-(thio)-theophylline (8-TTH 2 ), 8-(benzylthio)-theophylline (8-BzTTH) and 8-(methylthio)-theophylline (8-MTTH). All of the complexes have been studied by IR and multinuclear ( 1 H, 31 P, 13 C NMR) spectroscopy. A representative example of a Pd complex, [cis -Pd(8-BzTT) 2 (PPh 3 ) 2 ], has been authenticated by X-ray crystallography. In this complex square-pla- nar coordination about palladium occurs through two deprotonated N7 purine atoms cis to each other, and two triphenylphos- phine phosphorus atoms. In this paper, we present and discuss details of the synthesis, characterization and structural properties of the novel complexes. The synthesis and the characterization of 8-(benzylthio)-theophylline (8-BzTTH), a new organic ligands based on the molecular skeleton of 8-thio-purine, and a new procedure to obtain 8-(methylthio)-theophylline (8-MTTH) are also presented. © 2000 Elsevier Science S.A. All rights reserved. Keywords: Crystal structures; Palladium complexes; Purine base complexes 1. Introduction Studies on the interactions of metal ions with purine and pyrimidine bases are of paramount importance in bioinorganic chemistry due to the central role that these compounds have in the chemistry of nucleic acid derivatives [1]. Purines are multidentate ligands exhibit- ing a variety of potential donor groups and conse- quently behave as effective ligands for a wide range of metal ions. In fact, in addition to the N donor atoms, and to the carboxylate group, it has recently been shown that purine bases can even bind through C atoms. In particular, it has been demonstrated that the C(8) site in caffeine can efficiently coordinate to [Ru(NH 3 ) 3 Cl 2 ] [2a], [Os(NH 3 ) 5 ] [2b] and 9-(2-(2- aminoethylamino)ethyl)adenine [3] with [RuCl 2 - (DMSO) 2 ]. In order to study this very rare kind of interaction between purine bases and metals, that could be of biological relevance, the synthesis of new exam- ples of complexes exhibiting the C8 – metal interaction is of interest and largely desirable. In this regard, our group has recently shown a novel route to C8 Scheme 1. * Corresponding author. Tel./fax: +34-950-21 5008. 0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved. PII: S0020-1693(00)00177-8