Transformations of the Vaska-type complex trans-[RhCl(CO)(PTA)2] (PTA = 1,3,5-triaza-7-phosphaadamantane) during stepwise addition of HCl: Synthesis, characterization and crystal structure of trans-[RhCl2(PTA)(PTAH)]

The new aqua-soluble rhodium(I) complex trans-[RhCl2(PTA)(PTAH)] (1) {PTAH = N-protonated form of 1,3,5-triaza-7-phosphaadamantane (PTA)} has been synthesized via the reaction of trans-[RhCl(CO)(PTA)2] with aqueous HCl or N-chlorosuccinimide, or by the treatment of RhCl3 with PTA. Compound 1 has been characterized by IR, 1H and 31P{H} NMR spectroscopies, ESI–MS(+), elemental and single crystal X-ray diffraction analyses, the latter showing a square planar {RhCl2P2} geometry. Besides, the stepwise addition of diluted HCl to an aqueous solution of trans-[RhCl(CO)(PTA)2] has been monitored by 31P{1H} NMR and ESI–MS(+) techniques, allowing to detect a number of intermediate Rh(I) species.