title: Do solid-state structures reflect Lewis acidity trends of heavier group 13 trihalides? Experimental and theoretical case study.
abstract: Lewis acidity trends of aluminum and gallium halides have been considered on the basis of joint X-ray and density functional theory studies. Structures of complexes of heavier group 13 element trihalides MX(3) (M = Al, Ga; X = Cl, Br, I) with monodentate nitrogen-containing donors Py, pip, and NEt(3) as well as the structure of the AlCl(3)·PPh(3) adduct have been established for the first time by X-ray diffraction studies. Extensive theoretical studies (B3LYP/TZVP level of theory) of structurally characterized complexes between MX(3) and nitrogen-, phosphorus-, arsenic-, and oxygen-containing donor ligands have allowed us to establish the Lewis acidity trends Al > Ga, Cl ≈ Br > I. Analysis of the experimental and theoretical results points out that the solid state masks the Lewis acidity trend of aluminum halides. The difference in the Al-N bond distances between AlCl(3)·D and AlBr(3)·D complexes in the gas phase is small, while in the condensed phase, shorter Al-N distances for AlBr(3)·D complexes are observed with 9-fluorenone, mdta, and NEt(3) donors. The model based on intermolecular (H···X) interactions in solid adducts is proposed to explain this phenomenon. Thus, the donor-acceptor bond distance in the solid complexes cannot always be used as a criterion of Lewis acidity.
authors.affiliation: Inorganic Chemistry Group, Department of Chemistry, St. Petersburg State University, University Pr. 26, Old Peterhof, St. Petersburg 198504, Russia. alextim@AT11692.spb.edu
authors.forename: Alexey Y
authors.initials: AY
authors.lastname: Timoshkin
authors.forename: Michael
authors.initials: M
authors.lastname: Bodensteiner
authors.forename: Tatiana N
authors.initials: TN
authors.lastname: Sevastianova
authors.forename: Anna S
authors.initials: AS
authors.lastname: Lisovenko
authors.forename: Elena I
authors.initials: EI
authors.lastname: Davydova
authors.forename: Manfred
authors.initials: M
authors.lastname: Scheer
authors.forename: Christian
authors.initials: C
authors.lastname: Graßl
authors.forename: Alina V
authors.initials: AV
authors.lastname: Butlak