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 [{η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>N(H)Me<sub>2</sub>}<sub>2</sub>Co<sup>III</sup>]<sup>3+</sup>(Cl<sup>-</sup>)<sub>3</sub> (<b>3</b>) was obtained from C<sub>5</sub>H<sub>5</sub>(CH<sub>2</sub>)<sub>2</sub>NMe<sub>2</sub> (<b>1</b>) or from its salt M[C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>NMe<sub>2</sub>] (M = Na, Li) (<b>2</b>) upon reaction with Co<sup>II</sup>Cl<sub>2</sub> in THF. The structure of the complex [{(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>NMe<sub>2</sub>)(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>N(H)Me<sub>2</sub>)}Co<sup>III</sup>](PF<sub>6</sub>)<sub>2</sub> (<b>4</b>), prepared from <b>3</b> by treatment with NH<sub>4</sub>PF<sub>6</sub> in aqueous solutions, was solved in the triclinic space group <i>P</i>1̄ with one molecule in the unit cell, the dimensions of which were <i>a</i> = 6.314(2) Å, <i>b</i> = 7.137(2) Å, <i>c</i> = 13.452(2) Å, α = 103.66(2)°, β = 90.25(2)°, γ = 92.89(2)°, and <i>V</i> = 588.2(3) Å<sup>3</sup>. Adjacent molecules in the unit cell of <b>4</b> are hydrogen bonded via a H<sup>+</sup> through their −NMe<sub>2</sub> side chains. The reaction of Co<sub>2</sub>(CO)<sub>8</sub> with C<sub>5</sub>H<sub>5</sub>(CH<sub>2</sub>)<sub>2</sub>NMe<sub>2</sub> (<b>1</b>) leads to the formation of [{η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>NMe<sub>2</sub>}Co<sup>I</sup>(CO)<sub>2</sub>] (<b>5</b>). Treatment of <b>5</b> with HBF<sub>4</sub> in ether solutions yielded [{η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>N(H)Me<sub>2</sub>}Co<sup>I</sup>(CO)<sub>2</sub>]<sup>+</sup>BF<sub>4</sub><sup>-</sup> (<b>6</b>). Oxidation of <b>5 </b>with I<sub>2</sub> or Cl<sub>2</sub> gas yielded [{η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>NMe<sub>2</sub>}Co<sup>III</sup>I<sub>2</sub>] (<b>7a</b>) and [{η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>NMe<sub>2</sub>}Co<sup>III</sup>Cl<sub>2</sub>] (<b>7b</b>). Addition of HBF<sub>4</sub> to complex <b>7a</b> resulted in the breaking of the Co<sup>III</sup>-NMe<sub>2</sub> bond, producing the dimeric complex [{(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>N(H)Me<sub>2</sub>)Co<sup>III</sup>I<sub>2</sub>}<sub>2</sub>]<sup>2+</sup>(BF<sub>4</sub><sup>-</sup>)<sub>2</sub> (<b>9</b>). The bridged diiodo dimer <b>10</b>, [{(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>NMe<sub>2</sub>)CoI}<sub>2</sub>]<sup>2+</sup>(BF<sub>4</sub><sup>-</sup>)<sub>2</sub>, on the other hand, could be obtained from complex <b>7a </b>upon addition of AgBF<sub>4</sub> in CH<sub>2</sub>Cl<sub>2</sub>.