title: When the Tolman electronic parameter fails: a comparative DFT and charge displacement study of [(L)Ni(CO)₃](0/-) and [(L)Au(CO)](0/+).
abstract: In this study we have examined 42 [(L)M(CO)n](±/0) complexes (M = Ni and Au), including neutral ligands, such as phosphines and carbenes, and anionic ones. For each complex, the carbonyl stretching frequency (ν(CO)) and the amount of charge donated from the ligand to the metal (CT) have been computed on the basis of DFT calculations. For nickel complexes, the two observables nicely correlate with each other, as expected from the theory underlying the Tolman electronic parameter. On the contrary, for gold complexes a more complex pattern can be observed, with an apparent differentiation between phosphine ligands and carbon-based ones. Such differences have been explained analyzing the Au-L bond in terms of Dewar-Chatt-Duncanson bonding constituents (σ donation and π back-donation). Our analysis demonstrates that in linear gold(I) complexes, ν(CO) depends only on the metal-to-ligand π back-donation.
authors.affiliation: Istituto di Scienze e Tecnologie Molecolari del CNR (CNR-ISTM), c/o Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia , I-06123, Perugia, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Ciancaleoni
authors.forename: Nicola
authors.initials: N
authors.lastname: Scafuri
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bistoni
authors.forename: Alceo
authors.initials: A
authors.lastname: Macchioni
authors.forename: Francesco
authors.initials: F
authors.lastname: Tarantelli
authors.forename: Daniele
authors.initials: D
authors.lastname: Zuccaccia
authors.forename: Leonardo
authors.initials: L
authors.lastname: Belpassi