S-nitrosothiol and nitric oxide reactivity at β-diketiminato zinc thiolates
摘要:
The beta-diketiminato zinc halide [Me2NN]ZnCl2Li(THF)(3) (1) is prepared in 51% isolated yield by addition of the lithium beta-diketiminate Li[Me2NN] to ZnCl2 in THF. Reaction of 1 with 2 equiv. of the thallium thiolate TISCy provides {[Me2NN]Zn(mu-SCY)(2)TI}(2) (2), a TISCy adduct of [Me2NN]ZnSCy, as colorless crystals in 51% yield. Reaction of 1 with 1 equiv. TlSR provides the dinuclear {[Me2NN]Zn(mu-SR)}(2) (R = Cy (3), Bu-t (4)) which possess unsymmetrically bridging thiolate ligands with pairs of dissimilar Zn-S distances in the solid state (2.350(3) and 2.417(3) angstrom for 3; 2.312(1) and 2.415(1) angstrom for 4). Reaction of 1 with LiSCPh3 results in the mononuclear zinc thiolates [Me2NN]ZnSCPh3(THF) (5) and [Me2NN]ZnSCPh3 (6) with shorter, but similar Zn-SR distances of 2.225(2) and 2.214(1) angstrom. Variable temperature H-1 NMR studies of 3 and 4 in CDCl3 Suggest that the aliphatic thiolates exist predominately as monomeric species in solution near room temperature, though at -50 degrees C two different beta-diketiminato species are observed for 3. Thiolate exchange among 3, 4, and 6 also takes place on the NMR timescale near room temperature. Both 4 and 6 undergo transnitrosylation with CySNO in CDCl3 to give {[Me2NN]ZnSCy}(2) (3) and the corresponding S-nitrosothiol (BuSNO)-Bu-t or Ph3CSNO. Nitric oxide does not react with 4 or 6 under anaerobic conditions, but in the presence of O-2, NO cleaves the zinc-thiolate bond of 4 to rapidly give (BuSNO)-Bu-t. Similarly, anaerobic NO2 reacts with 4 to give (BuSNO)-Bu-t providing insight into the active nitrogen oxide species capable of cleaving Zn-SR bonds. (c) 2006 Elsevier B.V. All rights reserved.