Synthesis, characterization and coordination properties of bis(alkyl)selenosalen ligands

Abstract

New bis (alkyl) selenosalen podand ligands having Se2N2 donor sites have been synthesized by the condensation of unsymmetrical o-formylphenyl alkyl selenide (1-3) with ethylenediamine. The reaction of bis(alkyl)selenosalen podands with Pd(II) and Pt(II) afforded selenoether-selenolate coordination complexes 7-10via cleavage of one of the two Se-C(alkyl) bonds of bis(alkyl)selenosalen podands upon complexation. DFT calculations revealed that the cleavage of Se-C(alkyl) bonds occurred possibly via S(N)2 mechanism instead of a sequence of oxidative addition and reductive elimination reactions. The spectral data and elemental analyses confirmed the formation of selenoether-selenolate complexes. The structures of the podands N,N'-bis[(2-methylseleno)phenylmethylene]-1,2-ethanediamine (4), N,N'-bis[(2-decylseleno)phenylmethylene]-1,2-ethanediamine (5) and the selenoether-selenolate complex 8 have been determined by single crystal X-ray diffraction analysis. The crystal structure of 5 showed SeH interaction with a ladder like 3D supramolecular arrangement via interdigitation of long alkyl chains. Comparison of crystal packing of podands 4 and 5 indicates that the alkyl chain length has significant impact on the crystal packing. The platinum selenolate complex 8 shows a square planar arrangement around the Pt centre, where the Se atoms in the selenolate and the selenoether have nearly equal Pt-Se bond length.

Phthalocyanine Derivatives with Eight Peripheral Long‐Chain n‐Alkylseleno Substituents

“…The structure of 4‐chloro‐5‐ n ‐octylselenophthalodinitrile exhibits no unusual features. The selenium bond angle of 99.4(3)° and the Se–C(sp 2 ) and Se–C(sp 3 ) bond lengths of 1.892(7) and 1.963(6) Å, respectively, compare well with values determined for related compounds of the type ArSeR …”

Reaction time dependent formation of Pd(ii) and Pt(ii) complexes of bis(methyl)thiasalen podand

“…Previously, we reported the coordination properties of the analogous selenasalen ligand with Pd(II) and Pt(II). 8 When thiasalen ligand 9 was refluxed with Pd(C 6 H 5 CN) 2 Cl 2 in dry methanol for 3 h, the complex 11 was isolated as the predominant product with a small amount of complex 10. Therefore, the reaction of 9 with Pd(C 6 H 5 CN) 2 Cl 2 was repeated and the formation of products with respect to the reaction time was monitored.…”

“…To shed more light on our observation about the cleavage of one and/or both S-methyl groups sequentially, we have carried out DFT calculation (see theoretical methods). In our previous study, 8 we have shown that S N 2 substitution at the methyl group by the halide ion where the selenolate complex acts as a leaving group to eliminate the alkyl halide is the most likely reaction pathway for the dealkylation of selenoether upon complexation with Pd(II) and Pt(II). Experimentally we have observed the formation of alkyl halides in the complexation reaction of 2 and 3 with Pd(II) and Pt(II), respectively.…”

“…Experimentally we have observed the formation of alkyl halides in the complexation reaction of 2 and 3 with Pd(II) and Pt(II), respectively. 8 Previously, we have assumed the formation of a bis-selenoether complex analogous to 10•Cl 2 , as a reactant for the dealkylation via S N 2 reaction. Indeed, we have isolated now the analogous bisthioether complex 10•Cl 2 .…”

“…Earlier we 8 reported the complexation behaviour of bis-(alkyl)selenasalen podands 1-3 towards Pd(II) and Pt(II). The reaction of podands 1-3 with Pd(II) and Pt(II) afforded selenoether-selenolate complexes 4-7 via cleavage of one of the two Se-C(alkyl) bonds upon complexation.…”