Synthesis and Characterization of Novel Intramolecularly Base‐stabilized Boron Halides. Molecular Structures of 1‐X2BOCR1R2‐2‐NMe2C6H4 [R1 = R2 = Ph, X = Cl or F; R1 = R2 = Cy, X = Cl] and [1‐LiN(Ph)C(H)Ph‐2‐NMe2C6H4]2