On the Protonation of Ruthenium-PTA Complexes in Water. X-ray crystal structure of RuCl4(PTAH)2 4H2O (PTA = 1,3,5-triaza-7-phosphaadamantane)

The X-ray structure of the neutral RuCl4(PTAH)2·4H2O complex containing the N-protonated ligand PTAH (PTA = 1,3,5- triaza-7-phosphaadamantane) is presented. The protonated nitrogen atom of PTA forms strong hydrogen bonding with a water molecule, while another water acts as donor to an unprotonated nitrogen atom. The molecular structure of the neutral complex is compared with the cationic Ru(III) analogue previously described. It is shown that removing one electron from the HOMO practically alters neither the Ru-Cl and Ru-P distances nor the values of the angles around the metal atom.