FORMATION-CONSTANTS OF SOME PHOSPHINE AND PHOSPHITE ADDUCTS OF (ETA(5)-CYCLOPENTADIENYL) (SUBSTITUTED 1,2-ETHYLENEDICHALCOGENOLATO)COBALT(III) COMPLEXES AND THEIR H-1, C-13 AND P-31 NMR-SPECTRA

The formation constants of the phosphine and phosphite adducts of seve ral (eta(5)-cyclopentadienyl) (substituted 1,2-ethylenedithiolato)coba lt(III) complexes in acetonitrile were determined spectrophotometrical ly. The complexes with more electron-withdrawing substituents on the d itholate ligand form more stable adducts. The NMR chemical shifts (H-1 , C-13 and P-31) of the complexes, phosphines, phosphites and adducts were measured in CDCl3. The shifts were changed on adduct formation. T hese changes indicate that the phosphines act as sigma-donors and the phosphites as pi-acceptors and that the cobaltadithiolene ring, which is aromatic in the unbound complex, becomes olefinic in the adduct.