The synthesis of enantiomerically pure pyridine-bridged phosphaalkene-oxazolines ArP=C(Ph)(2,6-C(5)H(3)NOx) (1, Ar = Mes/Mes*, Ox = CNOCH(i-Pr)-CH2/CNOCH(CH2Ph)CH2) is reported. This new ligand forms a kappa(P), kappa(2)(NN) dimeric complex with copper(I) (7) that dissociates into a cationic kappa(3)(PNN) monomeric complex upon addition of a neutral ligand {[1a.CuL]OTf (8a-e): L = PPh3 (a), P(OPh)(3) (b), 2,6-lutidine (c), 4-DMAP (d), 1-methylimidazole (e)}. The P-Cu bond lengths in 8 are influenced by the pi-accepting/sigma-donating properties of L, and this can be observed by changes in the delta P-31(P=C) NMR shift. The donor-acceptor properties in complexes of type 8 have also been investigated by UV/vis spectroscopy and density functional theory calculations.