OCTAMETHYL-1,1-DIPHOSPHACHROMOCENE - ITS SPIN DISTRIBUTION AND OXIDATION

Octamethyl-1,1'-diphosphachromocene ((Tmp)(2)Cr) was prepared from (Tm p)K and chromium dichloride in 81% yield, According to X-ray analysis, it has a distorted sandwich structure with the P atoms being bent awa y from chromium. Large H-1, C-13, and P-31 NMR shifts established the similarity to chromocenes (S = 1) and negative spin on the ligands. Th e signal splitting and temperature-dependent H-1 NMR data revealed tha t, on the ligand, the spin sits predominantly at the phosphorus and tw o carbon atoms. In the cyclic voltammetry, two oxidation steps and one reduction were visible. After chemical oxidation, [(Tmp)(2)Cr](+)[B(C 6H5)(4)](-) was isolated in 65% yield. Its EPR spectrum is in accord w ith a S = 3/2 species. The H-1 NMR spectrum resembled those of chromoc enium ions. Its analysis and that of the temperature-dependent 1H NMR spectra indicated a rather uniform spin distribution within the ligand s. It was concluded that, in any case, the phosphorus may release spin to neighboring molecules.