The ligand precursors P(CH2NH-3,5-(CF3)(2)C6H3)(3) (1a), P(CH2NHPh)(3) (1b), and P(CH2NH-3,5-Me2C6H3)(3) (1c), react with the reagents Ti(NMe2)(4) and t BuNdTa(NEt2)(3) to generate metal complexes of the type P(CH2NArR)(3)TiNMe2 (2a - c) and P(CH2NArR)(3)TadN t Bu (3a-c) (where ArR)3,5-(CF3)(2)C6H3, Ph, and 3,5-Me2C6H3). Due to ring strain, the phosphine lone pair cannot chelate and is available to bind a second metal, and this feature can be utilized to synthesize heterometallic polynuclear complexes. The P-31 chemical shifts observed upon complexation of the early transition metals to the amido donors are large and in the opposite direction expected for the increased C-P-C bond angles in these complexes; these unusual shifts are due to P-Ti and P-Ta distances that are significantly shorter than the sum of van der Waals radii. The reaction of 2c with Ni(CO)(4) produces at first the bimetallic complex (CO)(3)Ni[P(CH2N-3,5-Me2C6H3)(3)TiNMe2] (4c), which gradually converts to the trimetallic complex (CO)(2)Ni[P(CH2N-3,5-Me2C6H3)(3)TiNMe2](2) (5c). The effect of the complexation of Ti and Ta fragments on the donor ability of the phosphine ligand was determined by the preparation of the bis-phosphine complexes trans-L2Rh-(CO) Cl, (where L) 1a-c, 2a-c, and 3a-c) prepared by the reaction of the appropriate phosphine with [Rh(CO) 2(mu-Cl)](2), and a measurement of the resultant CO stretching frequencies. Surprisingly, the complexes with the larger C-P-C angles are significantly poorer donors. Density functional theory calculations were performed to determine what factors affect the donor ability of the phosphine and if through-space interactions might play an important role in the observed electronic properties.