Ambiguous Role of N → Sn Coordinated Stannylene: Lewis Base or Acid?

peri-Substituted naphthalene derivatives 1-BCy2-8-SnL-C10H6 (5), 1-PPh2-8-SnL-C10H6 (6), and 1,8-(SnL)2-C10H6 (7) (L = 2,6-(Me2NCH2)2C6H3) were prepared. Compounds 5–7 allowed us to study the interactions between the tin atom from the LSn fragment with either Lewis acidic (BCy2) or Lewis basic sites (PPh2 and LSn). Moreover, addition of an external Lewis acid (BH3·SMe2) to 6 with different Sn/P donor atoms surprisingly provided the complex 1-PPh2-8-[(BH3)2L]­Sn-C10H6 (8), where both CH2NMe2 groups of the ligand L were coordinated by BH3 and as the consequence, P → Sn coordination exists in 8. The presence and type of the Y/Sn (P → Sn vs B ← Sn) interactions are described either experimentally or theoretically. The latter comprise determination of peri-interaction energies (PIE) as well as a variety of real-space bonding indicators (RSBI) derived from DFT calculations on the C/B–H corrected XRD structures of compounds 5–8. The electron density (ED) is topologically dissected according to the Atoms-In-Molecules (AIM) approach providing atomic volumes and charges as well as a bond paths motif, which also includes weak secondary contacts thereby transcending the Lewis picture of molecular bonding patterns.