Chelated Assisted Metal-Mediated N-H Bond Activation of β-Lactams: Preparation of Irida-, Rhoda-, Osma-, and Ruthenatrinems

2-Azetidinones substituted with pyridine (2a), quinoline (2b), isoquinoline (2c), imidazole (2d), and benzimidazole (2e) at the 4-position of the four-membered ring have been prepared in order to synthesize tribactams containing a transition metal and its associated ligands, LnM, at the 2-position of the tricyclic skeleton. The developed procedure is compatible with a wide range of transition-metal starting complexes. Thus, the iridium and rhodium dimers [M(eta(5)-C5Me5)Cl-2](2) react with 2a-e, in the presence of sodium acetate, to afford irida- and rhodatrinems (1a-j) containing the half-sandwich d(6) metal fragments M(eta(8)-C5Me5)Cl (M = Ir, Rh). The reactions of [M(mu-OMe)(eta(4)-COD)](2) (M = Ir, Rh) with 2a lead to irida- and rhodatrinems (1k,l) with the d(8) moieties M(eta(4)-COD). The coordination sphere and oxidation state of the metal center in these compounds can be modified, without affecting the 2-azetidinone backbone, by means of substitution and oxidative addition reactions. As a proof of concept, metallatrinems with the M(CO)(2) (M = Ir (1m), Rh (In)) and Ir(Me)I(CO)(2) (1o) units are also reported. Osmatrinems 1p,q containing the d(4) metal fragment OsH3((PPr3)-Pr-i)(2) have been obtained starting from the d(2) hexahydride OsH6((PPr3)-Pr-i)(2), by reaction with 2a,b, whereas the treatment of the tetrahydroborate complexes MH(eta(2)-H2BH2)(CO)((PPr3)-Pr-i)(2) (M = Os, Ru) with 2a yields osma- and ruthenatrinems (1r,s) containing six-coordinate bis(phosphine) d(6) metal fragments. The IR stretching frequency of the lactamic carbonyl, the bent angle between the five- and four-membered rings of the tricycle, and the N-CO bond length in the lactamic ring are clearly infuenced by the LnM fragment.