title: Large differences in secondary metal-arene interactions in the transition-metal dimers ArMMAr (Ar = terphenyl; M = Cr, Fe, or Co): implications for Cr-Cr quintuple bonding.
abstract: Quantum mechanical calculations, using both CASPT2 and DFT methods, for the model systems (MeMMMe, PhMMPh, (MeMMMe)(C6H6)2, Ar(S)MMAr(S), Ar (#)MMAr(#); M = Cr, Fe, Co; Ar(S) = C6H4-2(C6H5), Ar(#) = C6H3-2,6(C6H3-2,6-Me2)2) are described. These studies were undertaken to provide a multireference description of the metal-metal bond in the simple dimers MeMMMe and PhMMPh (M = Cr, Fe, Co) and to determine the extent of secondary metal-arene interaction involving the flanking aryl rings of the terphenyl ligands in quintuply bonded Ar'CrCrAr' (Ar' = C6H3-2,6(C6H3-2,6-Pr(i)2)2). We show that in the Cr-Cr species the Cr-arene interaction is a feeble one that causes only a small weakening of the quintuple bond. In sharp contrast, in the analogous Fe and Co species strong eta(6)-arene interactions that preclude significant metal-metal bonding are predicted.
authors.affiliation: Department of Chemistry, University of California, Davis, One Shields AVenue, Davis,California 95616, USA.
authors.forename: Giovanni
authors.initials: G
authors.lastname: La Macchia
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi
authors.forename: Philip P
authors.initials: PP
authors.lastname: Power
authors.forename: Marcin
authors.initials: M
authors.lastname: Brynda