A series of aluminum complexes supported by o-phenylene-derived amido phosphine ligands, N-(2-diphenylphosphinophenyl)-2,6-dimethylanilide ([Me-NP](-)) and N-(2-diphenylphosphinophenyl)-2,6-diisopropylanilide ([Pr-i-NP](-)), have been prepared. The reactions of trialkylaluminum with H[Me-NP] and H[Pr-i-NP], respectively, in refluxing toluene produced the corresponding dialkyl complexes [Me-NP]AIR(2) and [Pr-i-NP]AIR(2) (R = Me, Et). Deprotonation of H[Me-NP] with n-BuLi in THF at -35 degreesC followed by addition of AlCl3 in toluene at -35 degreesC afforded [Me-NP]AlCl2, which was subsequently reacted with 2 equiv of trimethylsilylmethyllithium in toluene to give [Me-NP]Al(CH2SiMe3)(2). The aluminum complexes were all characterized by H-1, C-13, P-31, and Al-27 NMR spectroscopy. The solid-state structures of monomeric, four-coordinate [Me-NP]AlEt2 and [Pr-i-NP]AlMe2 and five-coordinate [Me-NP]AlCl2(THF) were determined by X-ray crystallography. The H-1 NMR studies of [Me-NP]AlEt2, [Me-NP]Al(CH2SiMe3)(2), and [Pr-i-NP]AlEt2 indicate diastereotopic alpha-hydrogen atoms in these molecules. Heteronuclear COSY and NOE experiments suggest that the phosphorus donor in [Me-NP]Al(CH2SiMe3)(2) and [Pr-i-NP]AlEt2 is coupled to only one of the diastereotopic alpha-hydrogen atoms that is virtually antiperiplanar with respect to the phosphorus atom.