DERIVATE DES BOROLS VIII. (η5-BOROL)COBALT-KOMPLEXE

Article abstract of DOI:10.1016/0022-328X(87)80343-1

A large variety of (η⁵-borole)cobalt complexes have been prepared starting with μ-(CO)25-C4H4BR)>2(Co-Co) (IIIa: R = Me, IIIb: R = Ph), including inter alia, the sandwich complexes CpCo(η⁵-C4H4BR) (VIIa, b), the triple-decked complexes μ-(η⁵-C4H4BR)5-C4H4BR)>2 (VIIIa, b) and μ-(η⁵-C4H4BR)(FeCp)5-C4H4BR)> (X, R = Ph), the dinuclear complex μ-(CO)25-C4H4BPh)>(Fe-Co) (IX), and salts M5-C4H4BR)2> (XVa, b: M = Na; XVIa, b: M = NMe4; XVII: M = Cs, R = Ph).The anions 5-C4H4BR)2>(-) readily undergo stacking reactions to form multiple-decked complexes such as the triple-decked compounds μ-(η⁵-C4H4BR)(5-C4H4BR)> (XIIa, b), μ-(η⁵-C4H4BR)>5-C4H4BR)> (XVIII), <μ-(η⁵-C4H4BPh)5-C4H4BPh)>> (XX), and the quadruple-decker complex Ru<μ-(η⁵-C4H4BR)Co(η⁵-C4H4BR)>2 (XXI).The monofacially bound η⁵-borole ligands in VIIb and VIIIb sohw regiospecific H/D exchange, at the α position of the boron, on treatment with CF3CO2D at room temperature.VIIb undergoes a Friedel-Crafts substitution to give the 2-acetyl derivative XXIV with MeCOCl/SnCl4 in CH2Cl2 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 degree.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.