Reaction intermediates of cis-diammineaqua(hydroxo)platinum(II) with guanosine 5′-monophosphate characterized by proton nuclear magnetic resonance spectroscopy

Abstract

The reaction between guanosine 5′-monophosphate (GMP) and cis-[Pt(ND₃)₂(D₂O)(OD)]⁺ at pD 6.8 (I= 0.10 mol dm^–3 NaNO₃, 37 °C) has been examined by ¹H n.m.r. spectroscopy. The reaction proceeds with stoicheiometry GMP: Pt of 1.8:1.0 yielding N(7) bound cis-[Pt(ND₃)₂(GMP)₂]²⁺ as the predominant product. Proton n.m.r. spectra recorded as a function of time at various concentration ratios show two kinetically allowed intermediates along the reaction course. The first is a N(7) bound complex, cis-[Pt(ND₃)₂(GMP)(OD)]⁺, and the second can be best interpreted as cis-[{Pt(ND₃)₂}₂(GMP)₂]⁴⁺ in which each platinum atom is co-ordinated to N(7) of one GMP molecule and to O(6) of the other. In parallel experiments using trans-[Pt(ND₃)₂(D₂O)(OD)]⁺ and GMP the second intermediate is not formed.