Spectroscopic characterization of some unstable ortho-semiquinone and ortho-quinone complexes of Mn(I) by variable-temperature thin-layer spectroelectrochemistry at optically transparent electrodes
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- 作者：Hartl ; F.
- 关键词：Spectroelectrochemistry ; Manganese carbonyls ; Dioxolene complexes
- 刊名：Inorganica Chimica Acta
- 出版年：1995
- 出版时间：April, 1995
- 年：1995
- 卷：232
- 期：1-2
- 页码：99-108
- 全文大小：968 K
文摘
Four carbonyl complexes of MnI containing 3,5-di-tert.butyl-1,2-semiquinone (DBSQ) and 3,5-di-tert.butyl-1,2-benzoquinone (DBQ) ligands, the radicals [Mn(CO)3(L)(DBSQ)] and the cationic complexes [Mn(CO)3(L)(DBQ)]+ (L = H2O, PPh3), have been characterized for the first time by UV-Vis spectroscopy. These compounds possess limited stability at room temperature with the exception of [Mn(CO)3(PPh3)(DBSQ)] which thermally decomposes only in the presence of an excess of PPh3 Theo -(semi)quinone complexes under study were electrogenerated inside a recently developed low-temperature optically transparent thin-layer electrochemical (LT OTTLE) cell. The cell is ideally suited for UV-Vis and IR transmission spectroelectrochemical experiments at variable temperatures and allows the study of secondary reactions of the redox products. At T = 223 K, the CO disproportionation reaction of the complexes containing the H2O ligand, decomposition of the tricarbonyl DBQ complexes, and even substitution of the axial CO ligand in [Mn(CO)3(PPh3)(DBSQ)] by PPh3 were fully inhibited. The UV-Vis spectra indicate that the observed thermal lability of the o-quinone complexes [Mn(CO)4−n(L)n(DBQ)]+ (n = 0, 1; L = H2O, PPh3) most likely originates from a considerably weaker π-acceptor character of the DBQ ligand in these species than imposed in the stable, delocalized complex [Mn(CO)2(PPh3)2(DBQ)]+.