Synthesis and structural characterization of a monomeric di-copper-substituted silicotungstate [ﾎｳ-H2SiW10O36Cu2(ﾎｼ-1,1-N3)2]4- and the catalysis of oxidative homocoupling of alkynes.
英文:
Synthesis and structural characterization of a monomeric di-copper-substituted silicotungstate [ﾎｳ-H2SiW10O36Cu2(ﾎｼ-1,1-N3)2]4- and the catalysis of oxidative homocoupling of alkynes.
The di-copper-substituted ﾎｳ-Keggin silicotungstate with bis-ﾎｼ-1,1-azido ligands TBA4[ﾎｳ-H2SiW10O36Cu2(ﾎｼ-1,1-N3)2] (I, TBA = tetra -n-butylammonium) was synthesized in an aq. medium. The crystal structure of I showed that the anion part of I is a monomer of the basal-basal end-on diazido-bridged di-copper-substituted ﾎｳ-Keggin silicotungstate. The NMR and CSI-MS spectra of I in org. solvents, such as acetonitrile, benzonitrile, and 1,2-dichloroethane, showed that complex I was present as a monomer of the di-copper-substituted ﾎｳ-Keggin silicotungstate. Complex I could act as an effective homogeneous catalyst for the oxidative homocoupling of various types of alkynes, including arom., aliph., and heteroatom-contg. ones. The reaction possibly proceeds as follows: first, the ligand exchange proceeds between the azido groups in I and alkynyl groups to form the corresponding diyne with the reduced copper(I) species via the di-copper(II)-alkynyl intermediate, then the reduced species is reoxidized by mol. oxygen, and the oxidized species reacts with an alkyne to regenerate the alkynyl intermediate. [on SciFinder(R)]
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