N-O Ligand Supported Stannylenes: Preparation, Crystal, and Molecular Structures

A new series of tin(II) complexes (1, 2, 4, and 5) were successfully synthesized by employing hydroxy functionalized pyridine ligands, specifically 2-hydroxypyridine (hpH), 8-hydroxyquinoline (hqH), 10-hydroxybenzo[h]quinoline (hbqH) as stabilizing ligands. Complexes [Sn(μ-κ2ON-OC5H4N)(N{SiMe3}2)]2 (1) [Sn4(μ-κ2ON-OC5H4N)6(κ1O-OC5H4N)2] (2) are the first structurally characterized examples oxypyridinato exhibiting {Sn2(OCN)2} heterocyclic cores. As part our study, 1H DOSY NMR experiments undertaken using an external calibration curve (ECC) approach, with temperature-independent normalized diffusion coefficients, to determine nature oligomerisation 2 in solution. An experimentally determined coefficient (298 K) 6.87 × 10−10 m2 s−1 corresponds a hydrodynamic radius Ca. 4.95 Å. This is consistent observation averaged radii equilibria between dimeric [Sn{hp}2]2 tetrameric [Sn{hp}2]4 species at 298 K. Testing this hypothesis, regular intervals K–348 K show clear change calculated form Å 4.35 (348 tetramer ⇄ dimer which lies towards higher temperatures. Using these data, thermodynamic parameters for equilibrium (ΔH° = 70.4 (±9.22) kJ mol−1, ΔS° 259 (±29.5) J K−1 mol−1 ΔG°298 −6.97 (±12.7) mol−1) calculated. In course studies, Sn(II) oxo cluster, [Sn6(m3-O)6(OR)4:{Sn(II)(OR)2}2] (3) (R C5H4N) was serendipitously isolated, its molecular structure single-crystal X-ray diffraction analysis. However, attempts characterise complex multinuclear spectroscopy thwarted solubility issues, synthesise 3 on larger scale unsuccessful. contrast oligomeric structures observed 1 studies unambiguously establish monomeric 4-coordinate solid-state [Sn(κ2ON-OC9H6N)2)] (4) [Sn(κ2ON-OC13H8N)2)] (5).