New water-soluble azido- and derived tetrazolato-platinum(II) complexes with PTA. Easy metal-mediated synthesis and isolation of 5-substituted tetrazoles

The water-soluble four- and five-coordinate diazido-platinum(II) complexes cis-[Pt(N-3)(2)(PTA)(2)] (1) (PTA = 1,3,5-triaza-7-phosphaadamantane), cis-[Pt(N-3)(2)(Me-PTA)(2)]I-2 (2) ( Me-PTA = N-methyl-1,3,5-triaza-7-phosphaadamantane cation) and [ Pt( N3) 2( PTA) 3] ( 3) were obtained by reactions of cis-[Pt(N-3)(2)(PPh3)(2)] with PTA or [Me-PTA]I in dichloromethane. [2 + 3] cycloadditions of 1 with organonitriles NCR gave the bis( tetrazolato) complexes trans-[ Pt(N4CR)(2)(PTA)(2)] (R= Ph (4), 4-ClC6H4 (5) or 3-NC5H4 (6)), the reactions being greatly accelerated by microwave irradiation. 5-R-1H-Tetrazoles N4CR (R = Ph, 4-ClC6H4 and 3-NC5H4) were easily liberated from the tetrazolato complexes 4-6 and isolated in high yields, in a single-pot process, upon reaction with aqueous diluted HCl, with concomitant formation of the water soluble cis-[ Pt(Cl)(2)(PTA-H)(2)] complex 7. Alternatively, in a less convenient method, the tetrazoles could be liberated on reaction of 4-6 with propionitrile which also leads to the dicyano trans-[Pt(CN)(2)(PTA)(2)] complex 8. The compounds were characterized by IR, H-1, C-13 and P-31{H-1} NMR spectroscopies, FAB(+)-MS or ESI-MS, elemental analyses and (for 1 and 4) also by X-ray diffraction.