Synthesis and Coordination Chemistry of Main Group Pyridyl Ligands

Rincón Nocito, Marina
Wright, Dominic (dir.)

Universidad de Zaragoza, CIEN, 2021

Máster Universitario en Química molecular y Catálisis Homogénea

Resumen: The bis(2-pyridyl) ligands [Me2Al(6-Me-2-py)2Li·2THF] (40) and [Me2Al(5-Me-2-py)2Li·2THF] (44) were synthesized by reacting 2-bromo-6-methylpyridine and 2-bromo-5-methylpyridine, respectively, with nBuLi at ─78 °C (1:1 equiv), followed by reaction with Me2AlCl (2:1 equiv). Reaction with 2-bromo-3-methylpyridine was attempted (45), but the crystalline material [BrLi(6-Me-py)3] was obtained. Further experiments were tried, with different R-bridgehead groups (R = Et (41), Ph (42), tBu (43)) trying to be introduced. Although some of the reactions were believed to be successful, the isolation of the products was extremely difficult, given the oily nature of most of the obtained compounds, presumably by the presence of hydrolysed material. Substitution of the Li+ cation in 40 by Na+ (46) and K+ (47) by the reaction of 40 with NaOtBu or KOtBu (1:1 equiv), respectively, was also attempted, although neither of the reactions showed successful results.
Transmetallation reactions between 40 and various metals (Fe, Ca, Mn, Nb, Eu, Yb or Sm) did not yield any crystal structures. However, the reaction between the in situ ligand 41 and FeCl2 appeared to be successful. Unfortunately, no characterization analysis could be performed on it.
The synthesis of the already reported [Bi(4-py)3] ligand (48) by reaction of 4-bromopyridine with nBuLi (1:1 equiv), followed by reaction with BiCl3 (3:1 equiv) is described. Further reactions with Ni(BF4)2, NiBr2, Co(BF4)2 and CoBr2 are also mentioned, although the layering of the 48 solution and the different metal solutions did not yield any crystalline material that could be observed.
The NMR-scale reaction of 48 with [Bi(6-Me-2-py)3] (1:2 equiv) in d6-benzene and d8-THF was also attempted, although no change in the 1H NMR spectra could be observed, indicating that both reactions were unsuccessful.

Tipo de Trabajo Académico: Trabajo Fin de Master