Facile cleavage of organochalcogen hybrid (NEEN, NEN, EN, where E=Se or Te) ligand C-E and E-E bonds by Pd(II)

Abstract

The synthesis and characterization of chiral hybrid ligand R₂^∗Se₂ (R^∗=2-Me₂NCH(Me)C₆H₄) (9) and some of its derivatives is described. The reaction of 9 with a Pd(II) chloride complex leads to cleavage of the Se-Se bond and formation of the corresponding areneselenenyl chloride, R^∗SeCl (18). However, reactions of [RS; RS] and [SR; SR] bis[2-{1-(dimethylamine)ethyl}ferrocenyl] diselenides (7 and 8) with a Pd(II) chloride complex under identical conditions afford dinuclear complexes [PdCl{(SeC₅H₃CH(Me)NMe₂-2)Fe(C₅H₅)}]₂ (19 and 20). Reaction of achiral ditelluride, R₂Te₂ (R=2-Me₂NCH₂C₆H₄) (10), with a Pd(II) chloride complex gives a novel dinuclear complex, [PdCl(TeC₆H₄CH₂NMe₂-2)]₂ (21), and the dimeric tellurium complex (RTeCl)₂ (22), whereas the reaction of chiral Schiff base tridentate tellurium ligand R'₂Te (R'=2-C₆H₄CH=NCH(Me)C₆H₅) (11) with a Pd(II) chloride complex produces cleaved products (R'PdCl)₂ (23) and (R'TeCl)₂ (24). Similarly, the reaction between the tridentate ligand R₂Te (12) and Pd(COD)Cl₂ gives 22 and the dimeric palladium complex (RPdCl)₂ (25). The treatment of bidentate ligand RTeMe (13) results in decomposition of the ligand and precipitation of Te. All the compounds are characterized by detailed IR and NMR (¹H, ¹³C, ⁷⁷Se, and ¹²⁵Te) spectroscopic techniques, MS, and optical rotation measurements. The structures of R^∗SeBr (17), 21, 24, and 25 were determined by single-crystal X-ray crystallography. In 17 the coordination geometry around selenium is essentially T-shaped with a short Se···N distance (2.132(6) Å). The palladium tellurolato complex 21 crystallizes as a centrosymmetric dimer. Compound 23 crystallizes as a dimer in which each tellurium atom coordinates to two bridging chlorines, one nitrogen, and one carbon. Compound 25 crystallizes as a chloro-bridged centrosymmetric dimer.