The synthesis and complete characterization of the family of tetra(amine)bisphosphine ligands (o-NMe2C6H4)2P-(X)-P(o-NMe2C6H4)2, where X = CH2 (dmapm), (CH2)2 (dmape), and [Formula: see text] (dmapcp), are described. Crystal structure data are compared with known, analogous bisphosphines containing o-pyridyl or phenyl substituents in place of the o-dimethylanilinyl groups. Several short, intramolecular C-H···N distances in the anilinyl derivatives may represent the presence of weak hydrogen bonds. Key words: phosphine, amine, polydentate, hydrogen-bonding to N atoms.