Derivate des borols: VIII. (η 5-borol)cobalt-komplexe

Abstract

A large variety of (η 5-borole)cobalt complexes have been prepared starting with η-(CO) 2[Co(CO)(η 5-C 4H 4BR)] 2( CoCo) (IIIa: R = Me, IIIb: R = Ph), including inter alia, the sandwich complexes CpCo(η 5-C 4H 4BR) (VIIa, b), the triple-decked complexes η-(η 5-C 4H 4BR)[Co(η 5-C 4H 4BR)] 2 (VIIIa, b) and μ-(η 5-C 4H 4BR)(FeCp)[Co(η 5-C 4H 4BR)] (X, R = Ph), the dinuclear complex μ-(CO) 2[Fe(CO)Cp][Co(CO)(η 5-C 4H 4BPh)]( FeCo) (IX), and salts M[Co(η 5-C 4H 4BR) 2](XVa, b: M = Na; XVIa, b: M = NMe 4; XVII: M = Cs, R = Ph). The anions [Co(η 5-C 4H 4BR) 2] − readily undergo stacking reactions to form multiple-decked complexes such as the triple-decker compounds μ-(η 5-C 4H 4BR)[Mn(CO) 3][Co(η 5-C 4H 4BR)] (XIIa, b), μ-(η 5-C 4H 4BR)[Co(η 5-C 4H 4BR)][Rh(η-1,5-COD)] (XVIII), [NMe 3Ph][μ-η 5-C 4H 4BPh){Cr(CO) 3}{Co(η 5-C 4H 4BPh)}] (XX), and the quadruple-decker complex Ru[μ-(η 5-C 4H 4BR)Co(η 5-C 4H 4BR)] 2 (XXI). The monofacially bound η 5-borole ligands in VIIb and VIIIb shows regiospecific H/D exchange, at the α position of the boron, on treatment with CF 3CO 2D at room temperature. VIIb undergoes a Friedel-Crafts substitution to give the 2-acetyl derivative XXIV with MeCoCl/SnCl 4 in CH 2Cl 2 at room temperature. The structure of VIIIa, as determined by X-ray diffraction studies is that of a typical triple-decker compound with nearly coplanar rings. The three borole rings form a helix with torsional angles of 59.8 and 72.2°. All intra-ring bond distances of the central ligand are longer than those of the outer ligands. The metal-ligand interaction is somewhat stronger for the outer ligands than for the central ligand.