Generation and Tunable Cyclization of Formamidinate Ligands in Carbonyl Complexes of Mn(I): An Experimental and Theoretical Study

• Published in: Organometallics Vol. 38; no. 4; pp. 916 - 925
• Main Authors: Ruiz, Javier, Sol, Daniel, García, Lucía, Mateo, María A, Vivanco, Marilín, Van der Maelen, Juan F
• Format: Journal Article
• Language: English
• Published: American Chemical Society 25.02.2019
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.8b00898

A subtle change in the substituents at the nitrogen atoms in the N,N′-diarylformamidine complexes of formula fac-[Mn­(RNC­(H)­NHR)­(bipy)­(CO)3]+ (1a, R = phenyl; 1b, R = 4-dimethylaminophenyl) produces, upon deprotonation, either the monodentate formamidinate complex fac-[Mn­(PhNC­(H)­NPh)­(bipy)­(CO)3] (2a) or metallacylic complex 3b, which features a carbamoyl residue arising from nucleophilic attack to a vicinal carbonyl ligand. Complexes type 3 are also formed when using N-aryl-N′-alkyl-formamidines as well as N,N′-dialkylformamidines. Quantum Theory of Atoms in Molecules computations show the existence of a weak bond critical point of mainly noncovalent electrostatic type between the uncoordinated nitrogen atom of the formamidinate and a carbonyl ligand in 2a, which appears to be an isolable intermediate species that precedes the formation of metallacyclic complexes 3.