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[摘要]：The reaction of a potential mono(nucleobase) model adduct of cisplatin, cis-[Pt(NH3)2(1-MeC-N3)-(H2O)]2+ (6; 1-MeC: 1-methylcytosine), with the electrophile [Pd(en)(H2O)2]2+ (en: ethylenediamine) at pH u6 yields a kinetic product X which probably is a dinuclear Pt,Pd complex contg. 1-MeC--N3,N4 and OH bridges, namely cis-[Pt(NH3)2(1-MeC--N3,N4)(OH)Pd(en)]2+. Upon addn. of excess Ag+ ions, conversion takes place to form a thermodn. product, which, according to 1H NMR spectroscopy and x-ray crystallog., is dominated by a m-NH2 bridge between the PtII and PdII centers. X-ray crystallog. reveals that the compd. crystallizes out of soln. as a dodecanuclear complex contg. four PtII, four PdII, and four Ag+ entities: [{Pt2(1-MeC--N3,N4)2(NH3)2(NH2)2(OH)Pd2(en)2Ag}2{Ag(H2O)}2](NO3)10 ?H2O (10)is composed of a roughly planar array of the 12 metal ions, in which the metal ions are interconnected by m-NH2 groups (between Pt and Pd centers), m-OH groups (between pairs of Pt atoms), and metal-metal donor bonds (Pt瓵g, Pd瓵g). The four 1-methylcytosinato ligands, which are stacked pairwise, as well as the four NH3 ligands and parts of the en rings, are approx. perpendicular to the metal plane. Two of the four Ag ions (Ag2, Ag2') of 10 are labile in soln. and show the expected behavior of Ag+ ions in H2O, i.e., they are readily pptd. as AgCl by Cl- ions. The resulting pentanuclear complex [Pt2Pd2Ag(1-MeC-)2(NH2)2(OH)-(NH3)2(en)2](NO3)4? H2O (11) largely maintains the structural features of 1/2 of 10. The other two Ag+ ions (Ag1, Ag1') of 10 are remarkably unreactive toward excess NaCl. In fact, pentanuclear [Pt2Pd2AgCl-(1-MeC-)2(NH2)2(OH)(NH3)2(en)2]-(NO3)3?.5 H2O (12), obtained from 10 with excess NaCl, displays a Cl- anion bound to the Ag center (2.459(3) ? and is thus a rare case of a crystd. AgCl mol. |
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