Torubaev Yury V, Shaashua Omer, Braunstein Savion, Pappo Doron
Department of Chemistry, Ben-Gurion University of the Negev Beer-Sheva 84105, Israel.
Chemistry. 2025 May 8;31(26):e202404784. doi: 10.1002/chem.202404784. Epub 2025 Apr 17.
Coordination bonds are generally stronger than halogen bonds; however, the Jahn-Teller effect in d⁹ Cu(II) and the trans influence of the oxo-ligand in vanadyl (V═O) acetylacetonates can weaken N→Cu/V bonds, bringing them closer to the upper range of halogen bond strength. The study investigates the interactions between transition metal acetylacetonate complexes, M(acac)(L) (M─Cu(II), V(IV) = O; L = amine ligands), and halogen bond (XB)-donor co-formers, particularly 1,4-diiodotetrafluorobenzene (1,4-DITFB). The co-crystallization experiments reveal an unusual ligand displacement phenomenon wherein the expected M(acac)(L)·1,4-DITFB complexes fail to form, instead yielding separate M(acac)·1,4-DITFB and L·1,4-DITFB co-crystals. Computational studies reveal that while XB interactions alone may be insufficient to disrupt the M─N coordination bond, they can induce ligand displacement when amplified by the lattice stabilization of the resulting halogen-bonded co-crystals, particularly in Jahn-Teller distorted d⁹ Cu(II) and trans-influenced V(IV) = O complexes interacting with halogen bond donors.
配位键通常比卤键更强；然而，d⁹ Cu(II) 中的 Jahn-Teller 效应以及钒氧基（V═O）乙酰丙酮化物中氧代配体的反位影响会削弱 N→Cu/V 键，使其更接近卤键强度的上限。该研究调查了过渡金属乙酰丙酮化物配合物 M(acac)(L)（M = Cu(II)、V(IV)═O；L = 胺配体）与卤键（XB）供体共形成物之间的相互作用，特别是 1,4-二碘四氟苯（1,4-DITFB）。共结晶实验揭示了一种不寻常的配体取代现象，即预期的 M(acac)(L)·1,4-DITFB 配合物未能形成，而是生成了单独的 M(acac)·1,4-DITFB 和 L·1,4-DITFB 共晶体。计算研究表明，虽然单独的 XB 相互作用可能不足以破坏 M─N 配位键，但当它们因所得卤键合共晶体的晶格稳定作用而增强时，可诱导配体取代，特别是在与卤键供体相互作用的 Jahn-Teller 畸变 d⁹ Cu(II) 和反位影响的 V(IV)═O 配合物中。
