The stabilities of the toluene and THF solutions of complexes (Ar1BMe3)Li.OEt2 (I), Ar1 = C6H4CH2NMe2-2 and (Ar2BMe3)Li.OEt2 (II) and Ar2 = C6H4-(S)-CHMeNMe2-2 were investigated at various temperatures by means of H-1, Li-7, B-11, and C-13 NMR spectroscopy. I is stable in toluene and only inversion of configuration on nitrogen and on C(1) aromatic carbon was observed. II is less stable in toluene than I, and beside the intramolecular dynamic process dissociation with release of ether was detected. Complex I reacts with THF with donation of ether to THF and product IV, (Ar1BMe3)Li.THF, was isolated and characterized in toluene solution. IV reacts further with THF forming V, [LiMe]n.[THF], with cleavage of the LiC2B bond. II dissolved in THF leads to the (Ar2BMe3) (Li.nTHF) complex, VI. The mechanism of the bond cleavage of the LiC2B core in I and in II in the reaction with THF is discussed.
