Stable "inverse" sandwich complex with unprecedented organocalcium(I): crystal structures of [(thf)(2)Mg(Br)-C(6)H(2)-2,4,6-Ph(3)] and [(thf)(3)Ca{mu-C(6)H(3)-1,3,5-Ph(3)}Ca(thf)(3)]

Sven Krieck; Helmar Görls; Lian Yu; Markus Reiher; Matthias Westerhausen

doi:10.1021/ja808524y

Stable "inverse" sandwich complex with unprecedented organocalcium(I): crystal structures of [(thf)(2)Mg(Br)-C(6)H(2)-2,4,6-Ph(3)] and [(thf)(3)Ca{mu-C(6)H(3)-1,3,5-Ph(3)}Ca(thf)(3)]

J Am Chem Soc. 2009 Mar 4;131(8):2977-85. doi: 10.1021/ja808524y.

Authors

Sven Krieck¹, Helmar Görls, Lian Yu, Markus Reiher, Matthias Westerhausen

Affiliation

¹ Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller-Universitat Jena, August-Bebel-Strasse 2, D-07743 Jena, Germany.

PMID: 19193100
DOI: 10.1021/ja808524y

Abstract

The reaction of bromo-2,4,6-triphenylbenzene with activated magnesium in THF yielded the Grignard reagent [(thf)(2)Mg(Br)-C(6)H(2)-2,4,6-Ph(3)] (1) with a Mg-C bond length of 214.8(3) pm. A similar reaction of bromo-2,4,6-triphenylbenzene with activated calcium led to an "inverse" sandwich complex [(thf)(3)Ca{mu-C(6)H(3)-1,3,5-Ph(3)}Ca(thf)(3)] (2) with the calcium atoms on opposite sides of the central arene ring showing small Ca-Ca' and Ca-C distances of 427.9(3) and 259.2(3) pm. This extremely air- and moisture-sensitive complex exhibits thermochomic and solvatochromic behavior. It is paramagnetic with spin of S = 1 (triplet) with an ESR resonance at g = 2.0023. Quantum chemical calculations shed light on the bonding situation in this very unusual dinuclear Ca(I) compound.