Transition Metal Derivatives of a ((Dimethylamino)ethyl)cyclopentadienyl Ligand. Synthesis and Structures of Amino-Containing Cyclopentadienyl Derivatives of Cobalt(I) and -(III) Including Water-Soluble Compounds

The synthesis of monometallic cobalt(III) and -(I) complexes of ((dimethylamino)ethyl)cyclopentadienyl are reported. The presence of the basic amino group facilitates these synthesis using the corresponding cyclopentadiene complexes as starting material. A cobaltocenium green complex [{η5-C5H4(CH2)2N(H)Me2}2CoIII]3+(Cl-)3 (3) was obtained from C5H5(CH2)2NMe2 (1) or from its salt M[C5H4(CH2)2NMe2] (M = Na, Li) (2) upon reaction with CoIICl2 in THF. The structure of the complex [{(η5-C5H4(CH2)2NMe2)(η5-C5H4(CH2)2N(H)Me2)}CoIII](PF6)2 (4), prepared from 3 by treatment with NH4PF6 in aqueous solutions, was solved in the triclinic space group P1̄ with one molecule in the unit cell, the dimensions of which were a = 6.314(2) Å, b = 7.137(2) Å, c = 13.452(2) Å, α = 103.66(2)°, β = 90.25(2)°, γ = 92.89(2)°, and V = 588.2(3) Å3. Adjacent molecules in the unit cell of 4 are hydrogen bonded via a H+ through their −NMe2 side chains. The reaction of Co2(CO)8 with C5H5(CH2)2NMe2 (1) leads to the formation of [{η5-C5H4(CH2)2NMe2}CoI(CO)2] (5). Treatment of 5 with HBF4 in ether solutions yielded [{η5-C5H4(CH2)2N(H)Me2}CoI(CO)2]+BF4- (6). Oxidation of 5 with I2 or Cl2 gas yielded [{η5-C5H4(CH2)2NMe2}CoIIII2] (7a) and [{η5-C5H4(CH2)2NMe2}CoIIICl2] (7b). Addition of HBF4 to complex 7a resulted in the breaking of the CoIII-NMe2 bond, producing the dimeric complex [{(η5-C5H4(CH2)2N(H)Me2)CoIIII2}2]2+(BF4-)2 (9). The bridged diiodo dimer 10, [{(η5-C5H4(CH2)2NMe2)CoI}2]2+(BF4-)2, on the other hand, could be obtained from complex 7a upon addition of AgBF4 in CH2Cl2.