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

A series of mixed Pt11,Cu11 complexes derived from trans-[a2Pt(1-MeC-N3)2]2+ (a = NH3 or CH3NH − (1,2), OH− (3), NH3,H2O (4), coordinated to Pt via N3) and of general formula trans-[a2Pt(1-MeC−-N3,N4)2CuL]n+ with L = μ-CO32− (1,2), OH− (3), NH3,NH3H2O (4), 1-MeC-N3 (5), 9-EtGH-N7,H2O (6) have been isolated and characterized by X-ray analysis. In all compounds a trans-a2PtII entity is bound to two cytosine nucleobases via N3 sites each, whereas a CuII is bound to two monodeprotonated N4 sites. In all cases PtII represents a ligand of CuII, which either displays a distorted square-planar (1,2,3,5) or a pentacoordinate environment (4,6). PtIICuII distances are very short, ranging from 2.49 to 2.56 Å in 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.