868666-37-9Relevant academic research and scientific papers
New titanium complexes containing a cyclopentadienyl ligand with a pendant aminoalkyl substituent: Preparation, behavior of the amino group, and catalytic hydroamination of alkynes
Esteruelas, Miguel A.,Lopez, Ana M.,Mateo, A. Concepcion,Onate, Enrique
, p. 5084 - 5094 (2005)
Complex CpNTiCl3 (1) (CpN = C 5H4CH2CH2NMe2) reacts with 1.0, 2.0, and 3.0 equiv of MeMgCl to give CpNTiMeCl2 (2), CpNTiMe2Cl (3), and CpNTiMe3 (4), respectively. In the solid state, the amino group of the pendant substituent of the cyclopentadienyl ligand is weakly coordinated to the metal center (d(Ti - N) = 2.445(2) A in 2 and 2.433(4) A in 3), transoid disposed to a methyl ligand. In solution, the N-donor substituent is involved in a coordination-dissociation equilibrium (ΔH° = 2.4 ± 0.3 kcal·mol-1 and ΔS° = 6.5 ± 0.9 cal·mol-1·K-1 for 2, ΔH° = 3.8 ± 0.4 kcal·mol-1 and ΔS° = 12.3 ± 1.0 cal·mol-1·K-1 for 3, and ΔH° = 4.4 ± 0.1 kcal·mol-1 and ΔS° = 17.9 ± 0.4 cal·mol-1·K-1 for 4). In moist benzene, complex 3 affords the dinuclear species CpNTiCl(μ-O) 2ClTiCpN (5), containing a planar Ti2-(μ-O) 2 core. In the solid state, the pendant amino groups of 5 are also coordinated to the metal centers (d(Ti-N) = 2.421(2) A). Like in 2, 3, and 4, the amino groups of 5 are involved in a coordination-dissociation equilibrium (ΔH° = 4.9 ± 0.2 kcal·(mol of Ti) -1 and ΔS° = 20.7 ± 0.6 cal·K -1·(mol of Ti)-1). Complex 1 also reacts with LiNH(2,6-iPr2C6H3). The reaction leads to the six-coordinate amido-imido derivative {(2,6-iPr 2C6H3)NH}CpNTi{N(2,6- iPr2C6H3)} (6), which shows a strong coordination of the pendant amino group to the titanium atom (d(Ti-N amino) = 2.227(2) A). In solution the amino group remains coordinated. Complex 4 has been found to be an efficient catalyst precursor for the intermolecular regioselective anti-Markovnikov hydroamination of asymmetric alkynes. The reactions give enamineimine mixtures, which are transformed into the corresponding secondary amines.
