247214-56-8Relevant articles and documents
Self-Assembly of 3-[4′-(Diethylboryl)phenyl]pyridine and 3-[3′-(Diethylboryl)phenyl]pyridine: Synthesis, Structural Features, and Stability in Solution
Wakabayashi, Shigeharu,Sugihara, Yoshikazu,Takakura, Katsuto,Murata, Shigeru,Tomioka, Hideo,Ohnishi, Shiho,Tatsumi, Kazuyuki
, p. 6999 - 7008 (1999)
The self-assembly of 3-[4′-(diethylboryl)phenyl]pyridine (3) and 3-[3′-(diethylboryl)phenyl]pyridine (4) was investigated by 1H and 11B NMR spectroscopies and vapor pressure osmometry. It can be seen that in solution 3 affords an equilibrium mixture of oligomers including a cyclic trimer as a major component via intermolecular boron-nitrogen coordination bonds, which is supported by temperature-, concentration-, and solvent-dependent behaviors of 3. In contrast, 4 seems to afford a mixture of oligomers including a cyclic dimer in solution. Judging from the low coalescence temperature in variable-temperature NMR in toluene-d8 and easy scrambling with the corresponding 3-[(diethylboryl)pheny]-5-methoxypyridines at ambient temperature, it is concluded that the intermolecular boron-nitrogen coordination bonds made by 3 or 4 are weaker than those formed by 3-(diethylboryl)pyridine (1) or 2-(diethylboryl)-5-methylpyridine (2). Poor thermal stability was supported by electrospray mass spectrometry and structural analyses utilizing a semi-empirical molecular orbital calculation AM1. It is noted that in the assembly of 4 there is a tendency to maintain high tetrahedral character at the boron atom in the complex at the expense of strain energy. Thus, these features of 3 and 4 in solution are in marked contrast to those of 1 and 2.
