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 (BH_3·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.