The unexpected tridentate role of the tripodal ligand N-(carbamoylmethyl)iminodiacetato(2−) (ADA) in a new mixed-ligand nickel(II) complex with 2,2 ′-bipyridine (bipy) as secondary ligand: structure of [Ni(ADA)(bipy)(H 2O)]·4H 2O

• Published in: Inorganic chemistry communications Vol. 5; no. 9; pp. 727 - 729
• Main Authors: Bugella-Altamirano, E, González-Pérez, J.M, Choquesillo-Lazarte, D, Carballo, R, Castiñeiras, A, Niclós-Gutiérrez, J
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2002
• Subjects: Amide; Bipyridine; Denticity; Iminodiacetate; Ligand conformation; Nickel complex; Bipyridine; Denticity; Amide; Ligand conformation; Nickel complex; Iminodiacetate
• ISSN: 1387-7003; 1879-0259
• DOI: 10.1016/S1387-7003(02)00552-X

Text and pictogram for subject index entry: The structural study of [Ni(ADA)(bipy)(H 2O)]·4H 2O (ADA = N-(carbamoylmethyl)iminodiacetato(2−) ligand) reveals an unexpected ADA-tridentate role, with a free N-(2-amidomethyl) arm. That is in contrast to the tripodal–tetradentate ADA 2− reported for all metal–ADA complexes of known structures and is explained by ligand conformation comparison in three Ni(II)–ADA chelates. The crystal structure of a new mixed-ligand nickel(II) complex of N-(carbamoylmethyl)iminodiacetato(2−) (ADA) and 2,2 ′-bipyridine (bipy), with formula [Ni(ADA)(bipy)(H 2O)]·4H 2O (compound 3), reveals an unexpected tridentate ADA ligand, with a free N-(2-amidomethyl) arm, in contrast with all other known structures of metal–ADA chelates which have ADA 2− as tripodal–tetradentate ligand. This finding is explained on the basis of a structural comparison with the compounds of [Ni(ADA)(H 2O) 2] (1) and [ Ni( ADA)( Him )( H 2 O)]·1.5 H 2 O (2, Him = imidazole) which reveals significant changes in Ni–N(amino tertiary) and Ni–O(amide) bond lengths as well as in the ADA denticity and ligand conformation concerning the iminodiacetato(2−) moiety (IDA) in these Ni(II) chelates. The ADA-ligand conformation is mer-IDA + O(amide), fac-IDA + O(amide) or only fac-IDA-tridentate in 1, 2 or 3 respectively.