Oxidation of the a-pyridonate- (C5H4NO-) bridged diplatinum(II) complex [Pt2(en)2(C5H4NO)2]2+(2), where en = ethylenediamine, in nitric acid leads to the formation of a metal-metal-bonded diplatinum(III) complex, [Pt2(en)2(C5H4NO)2(NO2)-(NO3)]2+(1). In the structure of 1, two (ethylenediamine)diplatinum(III) units are linked by a metal-metal single bond and two a-pyridonate ligands bridging in a head-to-head fashion. The 2.6382 (6) A Pt-Pt bond axis is capped by nitrite, Pt-N = 2.109 (1) A, and nitrate, Pt-O =2.307 (9) A, ligands. These Pt-axial ligand distances nicely illustrate a structural trans influence mediated by the metal-metal bond. The coordinated nitrite group is disordered over two positions about the Pt-N axis and is bonded to the platinum atom having two N- and two O-donor ligands. As shown by 195Pt NMR spectroscopy, 1 has a binuclear, metal-metal-bonded structure in freshly prepared aqueous or dimethylformamide (DMF) solutions. In DMF the platinum resonances occur at +541 (PtN302) and -1141 (PtN40) ppm from [PtCl6]2-, with J(195Pt-l95Pt) = 6850 Hz. Decomposition of 1 to form 2 occurs slowly in solution, as revealed by 195Pt NMR spectroscopy. Reductive elimination of nitrite (N02-) to form the nitronium (N02+) ion is postulated to explain this decomposition, since nitrobenzene or p-nitrophenol is generated in aqueous solutions of 1 containing tetraphenylborate or phenol, respectively. The nitrate salt of compound 1, crystallizes in the monoclinic space group with a = 17.934 (1) A, b = 11.491 (1) A, c = 13.507 (1) A, ß= 108.84 (1)°, V = 2634 A3, Z = 4, pcalcd= 2.369 g cm-3, and pobsd = 2.379 (5) g cm-3. The structure was refined to R = 0.035 using 2686 diffractometer.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry