The synthesis, derivatization and coordination behavior of a new aminobis(diphosphonite), PhN{P(OC 6 H 4 OMe-o) 2 } 2 (1) is described. The ligand 1 reacts with H 2 O 2 , elemental sulfur or selenium to give the corresponding dichalcogenides PhN{P(E)(OC 6 H 4 OMe-o) 2 } 2 (E=O, 2; S, 3; Se, 4) in good yield. Reactions of 1 with Mo(CO) 6 , Pd(NCCH 3 ) 2 Cl 2 and Pt(COD)Cl 2 resulted in the formation of the chelate complexes, Mo(CO) 4 [PhN{P(OC 6 H 4 OMe-o) 2 } 2 ] (5) and MCl 2 [PhN{P(OC 6 H 4 OMe-o) 2 } 2 ] (M=Pd,7; M=Pt, 8) whereas in the reaction of 1 with [CpFe(CO) 2 ] 2 , one of the P–N bonds cleaves due to the metal assisted hydrolysis to give a mononuclear complex, [CpFe(CO){P(O)(OC 6 H 4 OMe-o) 2 }{PhN(H)(P(OC 6 H 4 OMe-o) 2 )}] (6). The molecular structures of 1, 4, 5 and 6 are determined by X-ray studies.