Syntheses, antitumor activity, and molecular mechanics studies of cis-PtCl2(pzH)2 (pzH=pyrazole) and related complexes. Crystal structure of a novel Magnus-type double-salt [Pt(pzH)4][PtCl4][cis-PtCl2(pzH)2]2 involving two perpendicularly aligned 1D chain

A new Magnus-type double-salt cocrystallized with a neutral complex, [Pt(pzH)4][PtCl4][cis-PtCl2(pzH)2]2 (1), has been isolated from a reaction between K2PtCl4 and pyrazole as a result of our reinvestigation of cis-PtCl2(pzH)2 (2). Interestingly, compound 1 involves two types of 1D chains respectively growing along the a- and c-axes, giving a novel intersecting framework. The former is {cis-PtCl2(pzH)2}n (PtPt=4.342(2) and 4.373(2) Å), and the latter is a Magnus-type 1D chain {[Pt(pzH)4][PtCl4]}n (PtPt=3.9388(1) Å). Each stacking interaction is stabilized with two hydrogen bonds formed between the chloride atoms and the NH units of pyrazoles; Cl⋯N(pyrazole)=3.21(2)–3.49(2) Å. The in vitro antitumor activity of 2 toward some human cancer cell lines is found to be comparable to that of cis-PtCl2(NH3)2. Molecular mechanics investigations of some GG-adducts of cis-Pt(pzH)2 reveal the importance of hydrogen-bond formation between the NH(pzH) units and the guanine/phosphate groups for the electrostatic stabilization of the adducts.