A bulky platinum triamine complex that reacts faster with guanosine 5'-monophosphate than with N-acetylmethionine.

A bulky platinum triamine complex, [Pt(Me(5)dien)(NO(3))]NO(3) (Me(5)dien=N,N,N',N',N''-pentamethyldiethylenetriamine) has been prepared and reacted in D(2)O with N-acetylmethionine (N-AcMet) and guanosine 5'-monophosphate (5'-GMP); the reactions have been studied using (1)H NMR spectroscopy. Reaction with 5'-GMP leads to two rotamers of [Pt(Me(5)dien)(5'-GMP-N7)](+). Reaction with N-AcMet leads to formation of [Pt(Me(5)dien)(N-AcMet-S)](+). When a sample with equimolar mixtures of [Pt(Me(5)dien)(D(2)O)](2+), 5'-GMP, and N-AcMet was prepared, [Pt(Me(5)dien)(5'-GMP-N7)](+) was the dominant product observed throughout the reaction. This selectivity is the opposite of that observed for a similar reaction of [Pt(dien)(D(2)O)](2+) with 5'-GMP and N-AcMet. To our knowledge, this is the first report of a platinum(II) triamine complex that reacts substantially faster with 5'-GMP than with N-AcMet; the effect is most likely due to steric clashes between the methyl groups of the Me(5)dien ligand and the N-AcMet.