Organoselenium( II ) halides containing the pincer 2,6-(Me 2 NCH 2 ) 2 C 6 H 3 ligand – an experimental and theoretical investigation

Abstract

New organoselenium( II )halidesofthetype[RSe] + X − [R = 2,6-(Me 2 NCH 2 ) 2 C 6 H 3 ;X=Cl( 2 ), Br ( 3 ), I ( 4 )] were prepared by cleavage of the Se – Se bond in R 2 Se 2 ( 1 )withSO 2 Cl 2 followed by halogen exchange when organo- selenium chloride was treated with NaBr or KI. The reaction between 2 and R ’ 2 MCl n resulted in new ionic [RSe] + [R ’ 2 MCl n +1 ] − [R ’ =2-(Me 2 NCH 2 )C 6 H 4 , n =1,M=Sb( 5 ), Bi ( 6 ); R ’ =Ph,M=Sb, n =1( 7 )or n =3( 8 )] species. All new compounds were investigated in solution by multinuclear NMR spectroscopy ( 1 H, 13 C, 77 Se, 2D experiments) and mass spectrometry. The ionic nature of 2 and the antimonates species was con fi rmed by conductivity studies. The molecular structures of [{2,6-(Me 2 NCH 2 ) 2 C 6 H 3 }Se] + Cl − · n H 2 O( 2 ·H 2 Oand 2 ·2H 2 O) and [{2,6-(Me 2 NCH 2 ) 2 C 6 H 3 }Se] + [Ph 2 SbCl 4 ] − ( 8 ), respectively, were established by single-crystal X-ray di ff raction, pointing out that the ionic nature of the se compounds is also preserved in the solid state, with both nitrogen atoms strongly trans coordinated to the selenium atom of the cation. Theoretical calculations carried out at the DFT level were exploite d to investigate the nature of the bonding in compounds 2 – 4 and the free cation [RSe] + ( 2a ). A topological analysis based on the theory of Atoms-In-Molecules (AIM) and Electron Localization Function (ELF) jointly to a Natural Bond Orbital (NBO) approach was used to shed light on the e ff ect of the nature of the halogen specie s X on the bonding within the 3c-4e N – Se – Nmoiety