Transition-Metal Derivatives of a Functionalized Cyclopentadienyl Ligand. 15.^† Synthesis and Structures of Amino Cyclopentadienyl Derivatives of Rhodium(I) and Rhodium(III) Including Water-Soluble Compounds

The synthesis of monometallic rhodium(III) and rhodium(I) derivatives of dialkylamino-functionalized cyclopentadienyl using the corresponding cyclopentadiene as starting material is facilitated by the presence of the basic amino group. This procedure affords the chloro salts of the substituted rhodicinium cation [(η5-C5H4(CH2)2NMe2H)2RhIII]3+ ([1][Cl]3) from the reaction of the [2-(dimethylamino)ethyl]cyclopentadiene with Na3RhIIICl6· 12H2O. Similarly the cationic half-sandwich complexes [(η5-C5H4(CH2)nNMe2H)RhI(cod)]+ (n = 2, [2][Cl], n = 3, [5][Cl]) are obtained from the reaction of the corresponding dialkylamino cyclopentadiene with [RhCl(cod)]2. These types of cationic complexes, 1, 2, and 5, bear pendant ammonium groups. The most classical procedure, starting from the lithium or more efficiently from the sodium cyclopentadienide salt, was used to synthesize neutral complexes [(η5-C5H4(CH2)nNMe2)RhI(cod)] (n = 2, 3; n = 3, 4). The structure of the chloride bis(hexafluorophosphate) salt, [(η5-C5H4(CH2)2NMe2H)2RhIII]3+(Cl-)(PF6-)2, ([1][Cl][PF6]2) was solved in the triclinic space group P1̄ with one molecule in the unit cell, the dimensions of which are a = 6.617(2) Å, b = 7.436(2) Å, c = 13.965(3) Å, α = 76.39(2)°, β = 82.31(3)°, γ = 87.26(2)°, and V = 661.8(3) Å3. The noncentrosymmetric character of this solid is attributed to the chloride ion. The tetrafluoroborate salt [(η5-C5H4(CH2)2NMe2H)RhI(cod)]+(BF4-) ([2][BF4]) crystallizes in the tetragonal space group P42/n with eight molecules in the unit cell, the dimensions of which are a = 21.183(2) Å, b = 21.179(3) Å, c = 8.324(2) Å, and V = 3734(1) Å3. Least squares refinement leads to values for the conventional R index of [1][Cl][PF6]2 (0.0484 for 2191 reflections used) and of [2][BF4] (0.0525 for 1083 reflections used); in both cases I > 3σ(I). As expected, compounds like [2][Cl]3, [1][Cl][PF6]2, [2][Cl], [2][BF4], [5][Cl], and [5][BF4] are soluble in water.