A new group of chiral monodentate diamidophosphite ligands (2 P-N/1 P-O bond) based on diazaphospholidine backbones derived from N,N 0 -dibenzylcyclohexane-1,2-diamine (7) and N, N 0 -dimethylcyclohexane-1,2-diamine (8), and diazaphosphepine backbones derived from N, N 0 -dimethyl-[1,1 0 -binaphthyl]-2,2 0 -diamine (9) and various chiral alkoxy groups (coming from phenylethanol a, borneol b, methyllactate c, allylic alcohol d, and methanol e) were prepared. The ligands have a highly modular structure, which is well suited to the synthesis of a small library. Preparation was readily accomplished by the successive addition of pure enantiomeric substituted diamine and pure enantiomeric alcohol to phosphorus trichloride. The corresponding diamidophosphite selenides Se(7-9) were prepared and the J PSe was calculated in order to evaluate the σ-donor ability of the new ligands. The reaction of [Pd(μ-Cl)(η 3 -2-CH 3 C 3 H 4 )] 2 with the new diamidophosphite ligands (7-9) led to the monomeric allylic neutral complexes 11-13. Two isomers appeared in solution due to the R-or S-geometry around the palladium atom. The molecular structure determined by X-ray diffraction of the neutral complex [PdCl(η 3 -2-CH 3 C 3 H 4 )(7a)] (11a-(S,S,S al )) showed a nonsymmetric coordination of the allyl moiety due to the greater trans influence of the phosphorus atom. The asymmetric hydrovinylation reaction between styrene and ethylene was tested using filtered CH 2 Cl 2 solutions of [PdCl(η 3 -2-CH 3 C 3 H 4 )L] complexes and AgBF 4 as catalytic precursors. The reaction performed at 15 °C and 15 bar of ethylene starting pressure led to good selectivities and moderate to good activities of 3-phenyl-1-butene. The best results were obtained when the cationic catalytic precursor contained the 9b-(R,S al ) diamidophosphite with a binaphthyl backbone and bornyloxy as the third substituent. With this system the TOF reached 595 h -1 of 3-phenyl-1-butene, whereas the ee was 90% toward the R-isomer.