Triprotonated 1,3,5-triaza-7-phosphaadamantane (PTA); fantasy or real intermediate on way from PTA to tetradentate tris(aminomethyl)phosphine?

In aqueous HBr solution (58% w/w), 1,3,5-triaza-7-phosphaadamantane (PTA) yielded the hitherto unknown triprotonated PTA, as single crystals. In addition, the same reaction mixture deposited crystals of [O = P(CH2NH3)(3)]Br-3 (2), formed presumably by ring opening of [PTA-H-3]Br-3 (3) and oxidation of the resulting [P(CH2NH3)(3)]Br-3 (1). The solid state structure of 2 and 3 were determined by X-ray diffraction. In water/methanol mixtures, reaction of 1 and [{(eta(6)-C10H14)RuBr2}(2)] yielded the half-sandwich [(eta(6)-C10H14)RuBr2{P(CH2NH3)(3)}]Br-3 (4) which -in aqueous solution- spontaneously afforded the dinuclear [(eta(6)-C10H14)RuBr2{mu(4)-P(CH2NH2)(3)}Ru(eta(6)-C10H14)]Br-2 (5).

Automated summary

In aqueous HBr solution, PTA yielded the triprotonated form and another compound. The solid state structures of some compounds were determined by X-ray diffraction.