Hepta‐Coordinated Mono‐ and Diorganotin(IV) Compounds with N3O2 Chelating Hydrazone Ligand

Hepta-coordinated organotin(IV) compounds with 2,6-diacetylpyridine bis(2-methylbenzoylhydrazone) ligand are synthesized and shown to adopt near-ideal pentagonal-bipyramidal geometries, featuring π-electron delocalization and potential for donor-stabilized cation formation.

A series of organotin(IV) complexes featuring the pro-ligand 2,6-diacetylpyridine bis(2-methylbenzoylhydrazone) (H₂L^Me) and various axial ligands have been synthesized. The reactions of H₂L^Me with R₂SnO (where R = Me, n-Bu, n-Oct, or t-Bu) and n-BuSnCl₃ in anhydrous toluene yielded the seven-coordinate complexes [Me₂Sn(L^Me)] (1), [n-Bu₂Sn(L^Me)] (2), [n-Oct₂Sn(L^Me)] (3), [t-Bu₂Sn(L^Me)] (4), and [n-BuSn(L^Me)Cl] (5), respectively. Subsequent treatment of complex 5 with NaN₃ and NH₄SCN afforded the corresponding isothiocyanate and azide derivatives, [n-BuSn(L^Me)N₃] (6), and [n-BuSn(L^Me)NCS] (7), respectively. Single crystal X-ray diffraction studies confirmed that the tin centers in complexes 1, 2, 4, 6, and 7 adopt a seven-coordinate geometry with a pentagonal bipyramidal configuration. The κ-N ³ O ² donor set of the ligand occupies the equatorial plane, while the axial positions are occupied by either two R groups, or one R group and one Cl, N₃, or NCS ligand, depending on the specific complex. In addition to X-ray diffraction analysis, all complexes 1−7 are characterized using Fourier transform infrared spectroscopy, high-resolution mass spectrometry , and solution-state Fourier transform nuclear magnetic resonance spectroscopy. The structural distortion within the SnN₃O₂ equatorial plane, attributed to positional shifts of the Sn(IV) center, are also discussed.

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