The synthesis of monometallic cobalt(III)) and -(II complexes of ((dimethylamino)ethyl)cyclopentadienyl are reported. The presence of the basic amino group facilitates these synthesis rising the corresponding cyclopentadiene complexes as starting material. A cobaltocenium green complex [{eta(5)-C5H4(CH2)(2)N(H)Me-2}(2)Co-III](3+) (Cl-)(3) (3) was obtained from C5H5(CH2)(2)NMe2 ii) or from its salt M[C5H4(CH2)(2)NMe2] (M = Na, Li) (2) upon reaction with (CoCl2)-Cl-II in TI IF. The structure of the complex [{eta(5)-C5H4(CH2)(2)NMe2)(eta(5)-C5H4(CH2)(2)N(H)Me-2)}Com(III)]-(PF6)(2) (4). prepared from 3 by treatment with NH4PF6 in aqueous solutions, was solved in the triclinic space group PI with one molecule in the unit cell, the dimensions of which were a = 6.314(2) Angstrom, b = 7.137(2) Angstrom, c = 13.452(2) Angstrom, alpha = 103.66(2)degrees, beta = 90.25(2)degrees, gamma = 92.89(2)degrees, and V = 588.2(3) Angstrom(3). Adjacent molecules In the unit cell of 4 are hydrogen bonded via a H+ through their -NMe2 side chains. The reaction of Co-2(CO)(8) with C5H5(CH2)(2)NMe2 (1) leads to the formation of [{eta(5)-C5H4(CH2)(2)NMe2}Co-I(CO)(2)] (5). Treatment of 5 with HBF4 in ether solutions yielded [{eta(5)-C5H4(CH2)(2)N(H)Me-2}Co-I(CO)(2)](+) BF4- (6). Oxidation of 5 with I-2 or Cl-2 gas yielded [{eta(5)-C5H4(CH2)(2)NMe2}(CoI2)-I-III] (7a) and [{eta(5)-C5H4(CH2)(2)NMe2}(CoCl2)-Cl-III] (7b). Audition of HBF4 to complex 7a resulted in the breaking of the Co-III-NMe2 bond, producing the dimeric complex [{eta(5)-C5H4(CH2)(2)N(H)Me-2)(CoI2)-I-III}(2)](2+) (BF4-)(2) (9). The bridged diiodo dimer 10, [{eta(5)-C5H4(CH2)(2)NMe2)CoI}(2)](2+) (BF4-)(2), on the other hand, could be obtained from complex 7a upon addition of AgBF4 in CH2Cl2.