Study of Donor–Acceptor Bonds on the N‐Coordinated Sn/Pb(II) Atoms in peri‐Substituted Naphthalenes: Evidence of Pb→B Interaction

Peri‐substituted naphthalene derivatives, namely, N‐coordinated plumbylenes 1‐PPh2‐8‐PbL‐C10H6 (4) and 1‐BCy2‐8‐PbL‐C10H6 (5) (L = 2,6‐(Me2NCH2)2C6H3) were prepared. Compounds 4 and 5 allowed studying interactions between the Pb atoms with the either Lewis acidic (BCy2) or Lewis basic sites (PPh2). Addition of an external Lewis acid (BH3·SMe2) to 5 provided the complex 1‐BCy2‐8‐[(BH3)2L]Pb‐C10H6 (7), in which both NMe2 groups of the ligand L were coordinated by BH3. This reaction has also been used for the synthesis of a tin analogue 1‐BCy2‐8‐[(BH3)2L]Sn‐C10H6 (6). New complexes 4–7 were also compared with the previously known, tin(II) analogues 1‐PPh2‐8‐SnL‐C10H6 (1), 1‐PPh2‐8‐[(BH3)2L]Sn‐C10H6 (2), 1‐BCy2‐8‐SnL‐C10H6 (3). This set of compounds allowed us to study influence of the P→E and E→B peri‐contacts upon the redox potentials E1/2 (ox1) by the cyclic voltammetry. As the result, the selective oxidation of E(II) atom was also studied and the new organotin(IV) sulfide [1‐PPh2‐8‐LSn(C10H6)(µ‐S)]2 (9) was prepared, the product of exclusive oxidation of the tin(II) atom in 1. Beside this, the evaluation of the P→E and E→B peri‐contacts in the neutral molecules, the first and second ionization energies (IE) were calculated. For this reason, electronic properties, full structural optimizations were conducted with density functional theory (DFT) for all possible combinations of metal atom (Sn vs. Pb), Lewis acid (N→Sn/Pb vs. N(BH3)Sn/Pb), peri‐substituents (BCy2 vs. PPh2), and for three molecular charges (0 vs. 1+ vs. 2+) on the B3PW91/6‐311+g(2df,p) level of theory. Synthesis of N‐coordinated plumbylenes as the peri‐substituted naphthalene allowed to study interactions between the Pb atom and B or P atom. The effect of strength of P→E and E→B donor–acceptor bonds on the redox potentials and ionization energies of E (E = Sn, Pb) was studied.