TY - JOUR

T1 - Alumazene adducts with pyridines

T2 - Synthesis, structure, and stability studies

AU - Löbl, Jiri

AU - Timoshkin, Alexey Y.

AU - Cong, Trinh

AU - Necas, Marek

AU - Roesky, Herbert W.

AU - Pinkas, Jiri

PY - 2007/7/9

Y1 - 2007/7/9

N2 - Lewis acid-base adducts of the alumazene [2,6-(i-Pr)2C 6H3NAlMe]3 (1) with pyridine (py) and 4-dimethylaminopyridine (dmap) were synthesized and structurally characterized: 1(py)2 (2), 1(py)3 (3), 1(dmap)2 (4), and 1(py)(dmap) (5). The bisadducts 2, 4, and 5 form the trans isomers. The trisadduct 3 exhibits an unexpected cis-cis isomer and can be prepared only in the presence of excess py. The planarity of the alumazene ring is lost upon coordination of the Lewis base molecules. A comparison of the Al-N(base) bond distances and pyramidality at Al suggests the higher basicity of dmap. NMR spectroscopy confirms stability to dissociation of the bisadducts in solution while the trisadduct 3 is labile and converts to 2. The thermodynamics of the adduct formation has been investigated experimentally and theoretically. Thermodynamic characteristics of the 1(py)n (n = 2, 3) dissociation reactions in the temperature range 25-200°C have been derived from the vapor pressure-temperature dependence measurements by the static tensimetric method. In all experiments, excess py was employed. Quantum chemical computations at the B3LYP/6-31G* level of theory have been performed for the 1(py) n and model complexes [HAINH]3(py)n (n = 1-3). Obtained results indicate that for the gas phase adducts upon increasing the number of py ligands the donor-acceptor Al-N(py) distance increases in accord with decreasing donor-acceptor bond dissociation energies.

AB - Lewis acid-base adducts of the alumazene [2,6-(i-Pr)2C 6H3NAlMe]3 (1) with pyridine (py) and 4-dimethylaminopyridine (dmap) were synthesized and structurally characterized: 1(py)2 (2), 1(py)3 (3), 1(dmap)2 (4), and 1(py)(dmap) (5). The bisadducts 2, 4, and 5 form the trans isomers. The trisadduct 3 exhibits an unexpected cis-cis isomer and can be prepared only in the presence of excess py. The planarity of the alumazene ring is lost upon coordination of the Lewis base molecules. A comparison of the Al-N(base) bond distances and pyramidality at Al suggests the higher basicity of dmap. NMR spectroscopy confirms stability to dissociation of the bisadducts in solution while the trisadduct 3 is labile and converts to 2. The thermodynamics of the adduct formation has been investigated experimentally and theoretically. Thermodynamic characteristics of the 1(py)n (n = 2, 3) dissociation reactions in the temperature range 25-200°C have been derived from the vapor pressure-temperature dependence measurements by the static tensimetric method. In all experiments, excess py was employed. Quantum chemical computations at the B3LYP/6-31G* level of theory have been performed for the 1(py) n and model complexes [HAINH]3(py)n (n = 1-3). Obtained results indicate that for the gas phase adducts upon increasing the number of py ligands the donor-acceptor Al-N(py) distance increases in accord with decreasing donor-acceptor bond dissociation energies.

UR - http://www.scopus.com/inward/record.url?scp=34547217425&partnerID=8YFLogxK

U2 - 10.1021/ic700488p

DO - 10.1021/ic700488p

M3 - Article

AN - SCOPUS:34547217425

VL - 46

SP - 5678

EP - 5685

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 14

ER -