Heteronuclear μ-1-methylcytosinato-N3,N4 complexes containing very short Pt→Cu dative bonds

A series of mixed Pt^IICu^II complexes derived from trans-[a₂Pt(1-MeC-N3)₂]²⁺ (a=NH3 or CH₃NH₂; 1-MeC=1-methylcytosine, coordinated to Pt via N3) and of general formula trans-[a₂Pt(1-MeC^--N3,N4)₂CuL]ⁿ⁺ with L=μ-CO₃^2- (1, 2), OH^- (3), NH₃,H₂O (4), 1-MeC-N3 (5), 9-EtGH-N7,H₂O (6) have been isolated and characterized by X-ray analysis. In all compounds a trans-a₂Pt^II entity is bound to two cytosine nucleobases via N3 sites each, whereas a Cu^II is bound to two monodeprotonated N4 sites. In all cases Pt^II represents a ligand of Cu^II, which either displays a distorted square-planar (1, 2, 3, 5) or a pentacoordinate environment (4, 6). Pt^II-Cu^II distances are very short, ranging from 2.49 to 2.56 Åin the six compounds. EPR spectra of frozen solutions have been examined in several cases. They appear, at least for 4a and 5, to be consistent with Pt-Cu hyperfine interactions rather than the presence of two different Cu-only species.