A Novel Series of Heteropolynuclear Metallomesogens: Organopalladium Complexes with Ferrocenophane‐Containing Ligands

Abstract

Ferrocenophane‐containing (Fcph) Schiff's bases p‐C12H25O(C6H4)CH=N(C6H4)Fcph (LAH) and p‐C12H25O(C6H4)COO(C6H4)CH=N(C6H4)Fcph (LBH) react with palladium(II) acetate to form μ‐acetato‐ and chloro‐bridged dimeric organopalladium complexes. By exchanging acetato‐groups with the chloride anions, μ‐chloro‐bridged heteropolynuclear dimers are obtained that show thermotropic smectic A phases over a temperature range of 198 to 260 °C. The complexes [PdClLA]2 and [PdClLB]2 can be transformed into a variety of mixed‐ligand PdII complexes by treatment with salicylaldimine p‐C12H25O(C6H4)COO(C6H3)(OH)CH=N(C6H4)Fcph (LCH) and β‐aminovinyl ketone p‐C12H25O(C6H4)COCH=CHNH(C6H4)Fcph (LDH). The obtained mixed‐ligand heterometallic complexes [PdLALC], [PdLBLC], [PdLALD] and [PdLBLD] exhibit enantiotropic, thermotropic nematic phases over a broad temperature range from 71 to 205 °C. The structures of the synthesized compounds were characterized by means of 1H NMR, IR and UV spectroscopy, as well as elemental analysis. The liquid crystalline properties were studied by polarising optical microscopy and DSC. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Silicon containing new salicylaldimine Pd(II) and Co(II) metal complexes as efficient catalysts in transformation of carbon dioxide (CO2) to cyclic carbonates

“…Characteristic absorptions in the FT-IR spectra of ligands and their Pd(II) and Co(II) metal complexes are represented by stretching vibrations of the n(C]N) group of ligands between 1632 and 1631 cm À1 . The low frequency shift of the n(C] N) stretch (in between 1616 and 1602 cm À1 for Pd(II) and 1614 and 1604 cm À1 for Co(II) complexes), in comparison with the free ligands, is consistent with N-coordination of Pd(II) and Co(II) ions to the azomethine ligands [32,33]. The coordination of the salicylaldimine ligands to the Pd(II) or Co(II) centre through the azomethine nitrogen atom is expected to the reduce the electron density in the azomethine link and lower the n(C]N) absorption frequency.…”

“…Calc. for C32 H 54 N 4 O 10 Si 2 Pd (F.W: 817 g/mol): C, 47.02; H, 6.66; N, 6.85. Found: C, 47.08; H, 6.58; N, 6.94%.…”

The orthopalladation dinuclear [Pd(L1)(μ-OAc)]2, [Pd(L2)(μ-OAc)]2 and mononuclear [Pd(L3)2] complexes with [N, C, O] or [N, O] containing ligands: Synthesis, spectral characterization, electrochemistry and catalytic properties

“…Characteristic absorptions in the spectra FT-IR of ligands and their Pd(II) metal complexes are represented by stretching vibrations of the CH@N group of ligands between 1629-1607 cm À1 . The low frequency shift of the CH@N stretch (in between 1614 and 1592 cm À1 ), in comparison with the free ligands, is consistent with N-coordination of Pd(II) ions to the azomethine ligands[32,36,37]. The coordination of the salicylaldimine ligands to the Pd(II) center through the azomethine nitrogen atom is expected to the reduce the electron density in theazomethine link and lower the t(C@N) absorption frequency.…”

“…Whereas, ligand L 3 H coordinates via the imine nitrogen atom and phenolic hydroxy atom. The cyclopalladation reaction with ligands L 1 H and L 2 H, which was carried out using palladium acetate in ethanol as described earlier for some other azomethine ligands [32], afforded l-acetato-bridged dimers [Pd(L 1 )(l-OAc)] 2 and [Pd(L 2 )(l-OAc)] 2 . In anhydrous ethanol, the phenolic OH function therefore remains unreactive towards Pd(II), allowing the ortho metallation reaction to take its own course -the Pd-C bond being unreactive [33].…”

Electrochemical and liquid crystal properties of ferrocene-based β-diketonato copper(II) and zinc(II) complexes

“…This has inspired many research groups to focus on molecular design and synthesis of new examples of heteropolynuclear metallomesogens [18][19][20][21][22]. bdiketones incorporating transition metals have been extensively studied due to their easier preparation, as well as known chemistries and/or rich structural varieties.…”