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.