Intramolecular Hydrogen-Bonded Tertiary Phosphines as 1,3,5-Triaza-7-phosphaadamantane (PTA) Analogues

New cationic trialkylphosphines [P(CH2NH2R){CH2N(R)CH2N(R)CH2}]+ (R = C6H5CH2, a; 4-FC6H4CH2, b), as their Cl− (1a, 1b), SbF6− (2a, 2b), and PF6− (3a, 3b) salts, are described. The phosphine framework is conformationally locked, in the solid state, through pairs of intramolecular N−H···N hydrogen bonds which are maintained in the RuII and RhIII complexes 4 and 5. Phosphines 1a−3b can be considered as charged variants of the well-known PTA ligand.