Fünffach koordinierte Komplexe vom Typ [tripodM-(ortho-(X)(Y)C₆H₄)]ⁿ (X, Y = O, S) bei d⁵-, d⁶- und d⁷-systemen. synthese, struktur, elektrochemie und esr-spektren / Five-coordinate complexes [tripodM-(ortho-(X)(Y)C₆H₄)]ⁿ (X, Y = O, S) with d⁵-,d⁶- and d⁷-Systems. Synthesis, Structure, Electrochemistry and ESR-Spectra

Abstract

The d 6 -Co(III)-species [tripodCo-(ortho-(X)(Y)C 6 H 4 )] + (X, Y = O, S, tripod = CH 3 C(CH 2 PPh 2 ) 3 ) 1 are reversibly reduced to the neutral d 7 -Co(II)-compounds [tripodCo-(ortho-(X)(Y)C 6 H 4 )] (X, Y = O, S) 2. Both species show fivefold coordination of cobalt with coordination polyhedra in between the limits of the square pyramid and the trigonal bipyramid respectively. The low-spin d 7 -species 2 give clearly resolved ESR-spectra revealing the coexistence of two geometric isomers above -80 °C, with only one isomer persistent at temperatures around 100 K. As an analogous d 5 -system [benzyltripodFe-(ortho-(S)(S)C 6 H 4 )] + 3 (benzyltripod = C 6 H 5 CH 2 C(CH 2 PPh 2 ) 3 ) has been obtained from [benzyltripodFe(NCCH 3 ) 3 ] 2+ and C 6 H 6 S 2 . Alternatively complexes of this type, e.g. [tripodFe-(ortho-(S)(S)C 6 H 4 )] + 4, may be prepared from Fe(H 2 O) 6 (BF 4 ) 2 /tripod/C 6 H 6 S 2 when the reaction mixture is activated by acidification with HBF 4 . The geometry of the d 5 -species 3 and 4 is close to a trigonal bipyramid