Liquid crystals based on palladium orthometallated complexes with amido or dialkyldithiocarbamato ligands

Abstract

The dinuclear cyclopalladated compounds [Pd₂(μ-OAc)₂(Lⁿ)₂] 2 derived from imines HLⁿ = p-C_nH_2n + 1OC₆H₄CH NC₆H₄OC_nH_2n + 1-p1 (n = 2, 6 or 10) react with NaOH to give dinuclear derivatives [Pd₂(μ-OH)₂(Lⁿ)₂] 3. The reaction of 3 with amines (1 ∶ 1 molar ratio) yields the corresponding hydroxo–amido complexes [Pd₂(μ-NHR)(μ-OH)(Lⁿ)₂] (R = C_mH_2m + 1 (m = 1, 6, 10, 14 or 18) 4 or C₆H₄C₁₄H₂₉-p5). With excess of amine [Pd₂(μ-NHR)₂(Lⁿ)₂] 6 (R = C_mH_2m + 1) are formed. Complexes 4 react with thiols or decanoic acid in 1 ∶ 1 mole ratio to give the corresponding amido–thiolato or amido–carboxylato complexes [Pd₂(μ-SC_jH_2j + 1)(μ-NHR)(Lⁿ)₂] 7 ( j = 4, 10 or 18) or [Pd₂(μ-O₂CC₉H₁₉)(μ-NHR)(Lⁿ)₂] 8. The mononuclear complexes [Pd(S₂CNR′₂)(Lⁿ)] (R′ = C₂H₅9a or C₈H₁₇9b) are prepared when complexes 3 are treated with dialkylamines in the presence of carbon disulfide. Most of the complexes show liquid crystal behaviour and nematic, smectic A and smectic C phases are found.