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

Abstract

The water-soluble four- and five-coordinate diazido-platinum(II) complexes cis-[Pt(N₃)₂(PTA)₂] (1) (PTA = 1,3,5-triaza-7-phosphaadamantane), cis-[Pt(N₃)₂(Me-PTA)₂]I₂ (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(N₃)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, ¹H, ¹³C and ³¹P{¹H} NMR spectroscopies, FAB⁺-MS or ESI-MS, elemental analyses and (for 1 and 4) also by X-ray diffraction.