Cobalt complexes with the 1-[2-(N,N-dimethylamino)ethyl]-2,3,4,5-tetramethylcyclopentadienyl ligand

Abstract

Some new Co(I), Co(II), and Co(III) complexes containing the 1-[2-(NN-dimethylamino)-ethyl]-2,3,4,5-tetramethylcyclopentadienyl ligand (Cp(AND)) are described. Dicobalt octacarbonyl reacts with Cp(AND)H to give dicarbonyl(eta5-1-[2-(NN-dimethylamino)ethyl]-2,3,4,5-tetramethyl-cyclop entadienyl)cobalt(I) (Cp(AND)CO(CO)2) With a noncoordinating dimethylamino function. Addition of iodine to Cp(AND)CO(CO)2 leads to the formation of the diiodocyclopentadienylcobalt complex CP(AND)CoI2 with intramolecular dimethylamino coordination. Cp(AND)CoI2 is formed via the diiodocarbonylcyclopentadienylcobalt complex Cp(AND)CO(CO)I2. Under ordinary conditions Cp(AND)CoI2 and CP(AND)CO(CO)I2 can easily be interconverted. Cp(AND)CoI2 does not react with ethylene. Reduction of Cp(AND)CoI2 With sodium amalgam under a CO atmosphere yields Cp(AND)CO(CO)2; under an ethylene atmosphere Cp(AND)CO(C2H4)2 with a noncoordinating dimethylamino group is formed. CP(AND)CO(C2H4)2 can also be synthesized by a different route: Reaction of CoCl2 with Cp(AND)Li yields the paramagnetic Co(II) dimer [Cp(AND)CoCl]2, which is subsequently reduced with sodium amalgam to Cp(AND)CO(C2H4)2. Structure investigations on Cp(AND)CoI2 confirm the intramolecular coordination of the dimethylamino group (crystal system: triclinic; space group P1BAR; a = 7.903(3) angstrom, b = 12.802(7) angstrom, c = 14.067(5) angstrom, alpha = 106.94(4)-degrees, beta = 92.12(3)-degrees, gamma = 107.55(4)-degrees; Z = 2).