COMPLEXES WITH 2 -SMN(CO)2CP CENTERS, SEPARATED RADICALS OR S-S BONDS

The complexes [L(CO)2MnSR].(L = Cp, Cp', Cp*) are without exception stable as mononuclear radical complexes. The compounds L(CO)2MnS(X)SMn(CO)2L (X = (CH2)2 1, (CH2)3 2, (CH2)4 3, 1,3-C6H4 4) were examined in order to find out whether a dimerization of the radicals [L(CO)2MnSR]. might be induced by intramolecular forces: 1 and 4 are diradicals while 2 and 3 are diamagnetic molecules containing S-S-bonds in relatively unstrained five and six membered cycles. NMR- and EPR-spektra show the partial rupture of these bonds. Cyclic voltammetry reveals two reversible oxidation peaks for all the compounds 1-4. Reversible reduction signals, however, are only observed for the complexes 1 and 4 which have no S-S-bond; the reduction of the compounds 2 and 3 is irreversible because it induces scission of the S-S-bond. The preparative oxidation of 4a (L = Cp') using AgPF6 leads to the tetranuclear dication [Cp'(CO)2Mn]2SC6H4S[Mn(CO)2Cp']2(2+) (5), the spectra of which document a trigonal planar coordination of both sulfur centers. The results are further substantiated by X-ray analyses of 2, 3 and 4.