This article describes the synthesis and characterization of novel cationic five-coordinate Pt(II) complexes containing nitrogen sugar-based ligands. The cytotoxicity of the complexes was evaluated on different cell lines with the expectation that both the coordinative saturation and the sugar moiety cooperate to enhance their biological activity. In fact, the complexes resulted to be more active than cisplatin but still with little selectivity. They activate the apoptosis pathway. Binding of representative compounds with DNA was studied by ethidium bromide displacement assay and circular dichroism. Binding to model proteins was also investigated; the X-ray structure of the adduct formed in the reaction between a representative compound and the model protein bovine pancreatic ribonuclease was obtained. The structure discloses an unprecedented interaction between a five-coordinate Pt(II) moiety and a His side chain.