Complexes of the [Re6(μ3-Se)8]2+ core-containing clusters with the water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) ligand: unexpected ligand protonation and related studies

Three new complexes of the [Re-6(mu(3)-Se)(8)](2+) core-containing clusters with the water-soluble trialkylphosphine ligand 1,3,5-triaza-7-phosphaadamantane (PTA), [Re-6(mu(3)-Se)(8)(PEt3)(5)(PTA)](SbF6)(2) (P5PTA, 1), [Re-6(mu(3)-Se)(8)(PEt3)(5)(PTAH)][Re-6(mu(3)-Se)(8)(PEt3)(5)(PTA)](SbF6)(5) (2), and [Re-6(mu(3)-Se)(8)(PEt3)(5)(PTAH)](2)(HBr)(SbF6)(2)Br-4 (3) have been prepared and structurally characterized. Unexpected protonation of the cluster-bound PTA ligand was observed when coordination of 1 with HgI2 was attempted, affording compound 2 featuring a protonated PTA ligand, PTAH. Deliberate acidification of 1 with HBr produced compound 3, and the protonation was investigated by using P-31 NMR spectroscopy. Crystallographic studies revealed distinct structural distortions of the ligand as a result of protonation.