Palladium(II) and platinum(II) complexes of β-functionalized ethyl selenolates: Effect of substitution on synthesis, reactivity, spectroscopy, structures and thermal behavior

Sodium ethylselenolates with functional groups X (where X = –OH, –COOH, –COOMe and –COOEt) at β-carbon were prepared in situ by reductive cleavage of corresponding diselenide with NaBH4 either in methanol or aqueous ammonia. Treatment of these selenolates with [M2Cl2(μ–Cl)2(PR3′)2] (M = Pd or Pt; PR3′ = PMePh2, PnPr3) in different stoichiometry yielded various bi- and tri-nuclear complexes. The homoleptic hexanuclear complexes [Pd(μ–SeCH2CH2X)2]6 (X = OH, COOH, COOEt), were obtained by reacting Na2PdCl4 with NaSeCH2CH2X. All these complexes have been fully characterized. Molecular structures of ethylselenolates containing hydroxyl and carboxylic acid groups revealed solid state associated structures through inter-molecular hydrogen bond interactions. Trinuclear complex, [Pd3Cl2(μ–SeCH2CH2COOH)4(PnPr3)2] (3a), was disposed in a boat form unlike chair conformation observed for the corresponding methylester complex. The effect of β-functionality in ethylselenolate ligands towards reactivity, structures and thermal properties of palladium and platinum complexes has been extensively studied.

Graphical abstractA series of mono-, bi- and poly-nuclear palladium and platinum complexes have been synthesized by employing β-substituted ethylselenolate ligands. β-Substitution results in different nucleophilicity of ethylselenolate ligands which is reflected on reactivity, structures and thermal behavior of palladium and platinum complexes. Presence of protic groups in XCH2CH2Se− (X = OH, COOH) modified the solid state structures which exhibited functional group mediated aggregation via hydrogen-bonding.Figure optionsDownload full-size imageDownload as PowerPoint slide