Flash Communication: On the Bistabilities and Reactivities of ortho-Phenylene Compounds with Ch═O→B Interactions

Intramolecular Lewis adducts, especially those bearing a boron Lewis acid and a phosphine oxide Lewis base, have become attractive motifs for tunable luminescence properties in materials. However, intramolecular Lewis adducts with Ch(IV)═O moieties (Ch = chalcogen) as Lewis bases are under-represented in the field. Here, we describe the syntheses of two chalcogen boranes of general formula o-(PhCh)(BMes₂)C₆H₄ (Ch = S (1), Se (2)) and their conversions into the corresponding chalcogen-oxide boranes of general formula o-(PhCh═O)(BMes₂)C₆H₄ (Ch = S (3), Se (4)). While both 3 and 4 form inner adducts held by Ch═O→B dative bonds in the solid state and in solution, we examine the bistabilities of these interactions computationally and experimentally. Interestingly, the reaction of 4 and HF·pyridine gives rise to o-(SePhMes)(BF₃)C₆H₄ (5) which shows evidence for F→Se intramolecular chalcogen bonding.