The 4,5‐{Ph2(HO)C}2‐1,2,3‐triazole ligand (2) with two bulky Ph2C(HO) substituents was synthesized and used in the preparation of coordination compounds with selected group 1 metals. In the solid state, the high Lewis acidity of lithium caused the formation of di‐ and tetrametallic L2Li2thf4·2THF and L4Li4thf2(Et2O)2·2Et2O (L = monoanionic form of 2) species, while only the dimetallic derivative L2Na2thf4·2THF was observed for sodium. The larger size of potassium caused the formation of L6K6(H2O)thf2·2THF with a hexagonal drumlike inorganic core. 1H DOSY NMR spectroscopic studies confirmed the presence of multimetallic species also in solution. The molecular structures of the compounds were determined by single‐crystal X‐ray diffraction. In a comparative study, magnesium derivatives of 2 were prepared to evaluate the effect of a higher covalent character of the M–O bond leading to multimetallic polycyclic systems with up to 29 rings. Finally, the lithium compounds showed catalytic activity in the polymerization of ε‐caprolactone.
The
molecular meso-metallaporphyrin has been obtained
from the reaction of AlMe3 with the bulky 4,5-(Ph2(HO)C)2-1,2,3-triazole (1). The presence
of Al–Me groups coordinated to the triazole rings creates three
different stereoisomers that were identified by single-crystal X-ray
diffraction. Further studies revealed that, for steric reasons, only
one of the two main stereoisomers is active in the polymerization
of ε-caprolactone. When GaMe3 is used instead of
AlMe3, a trimetallic species is formed instead of the meso-metallaporphyrin pointing to a metal-directed self-assembly.
On the other hand, the reaction of the monolithium salt [{Li(THF)2}{κ2-N,N′-4,5-(Ph2(HO)C)-1,2,3-triazole}]2 (2; THF = tetrahydrofuran) with MCl3 (M = Al, Ga)
yields meso-metallaporphyrin species with a lithium
atom in the center of the metallacycle. While the gallium derivative
is rather stable in solution, the aluminum analogue decomposes rapidly.
In the solid state, continuous cationic columns running throughout
the whole crystal are formed from alternating Li⊂[M]4 (M = Al, Ga) meso-metallaporphyrin and [Li(THF)4]+ cations. Density functional theory calculations
determined that the weak Cl···H, H···H,
N···H, and Cl···O interactions with
a total interaction energy of −38.6 kcal·mol–1 are responsible for this unusual packing.
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