Isomeric Olefin Tetracarbonyl Complexes of Tungsten(I): An Infrared Spectroelectrochemical Study at Low Temperatures
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- 作者：Marcin Gó ; rski ; Franti
//pubs.acs.org/images/entities/scaron.gif" border="0">ek Hartl ; Teresa Szyma
- 刊名：Organometallics
- 出版年：2007
- 出版时间：July 30, 2007
- 年：2007
- 卷：26
- 期：16
- 页码：4066 - 4071
- 全文大小：87K
- 年卷期：v.26,no.16(July 30, 2007)
- ISSN：1520-6041
文摘
In situ electrolysis within an optically transparent thin-layer electrochemical (OTTLE) cell was appliedat 293-243 K in combination with FTIR spectroscopy to monitor spectral changes in the carbonylstretching region accompanying oxidation of four tetracarbonyl olefin complexes of tungsten(0), viz.,trans-[W(CO)4(
gifchars/eta.gif" BORDER=0 >2-ethene)2], trans-[W(CO)4(gifchars/eta.gif" BORDER=0 >2-norbornene)2], [W(CO)4(gifchars/eta.gif" BORDER=0 >4-cycloocta-1,5-diene)], and[W(CO)4(gifchars/eta.gif" BORDER=0 >4-norbornadiene)]. In all cases, the one-electron-oxidized radical cations (17-electron complexes)have been identified by their characteristic gifchars/nu.gif" BORDER=0 >(C
gif">O) patterns. For the bidentate diene ligands, the cisstereochemistry is essentially fixed in both the 18- and 17-electron complexes. The radical cation of thetrans-bis(ethene) complex was observed only at 243 K, while at room temperature it isomerized rapidlyto the corresponding cis-isomer. The thermal stability of the three studied radical cations in the cisconfiguration correlates with the relative strength of the W-CO bonds in the positions trans to the olefinligand, which are more affected by the oxidation than the axial W-CO bonds. For the bulky norborneneligands, their trans configuration in the bis(norbornene) complex remains preserved after the oxidationin the whole temperature range studied. The limited thermal stability of the radical cations of the trans-bis(alkene) complexes is ascribed to dissociation of the alkene ligands. The spectroelectrochemical resultsare in very good agreement with data obtained earlier by DFT (B3LYP) calculations.
gifchars/eta.gif" BORDER=0 >2-ethene)2], trans-[W(CO)4(gifchars/eta.gif" BORDER=0 >2-norbornene)2], [W(CO)4(gifchars/eta.gif" BORDER=0 >4-cycloocta-1,5-diene)], and[W(CO)4(gifchars/eta.gif" BORDER=0 >4-norbornadiene)]. In all cases, the one-electron-oxidized radical cations (17-electron complexes)have been identified by their characteristic gifchars/nu.gif" BORDER=0 >(Cgif">O) patterns. For the bidentate diene ligands, the cisstereochemistry is essentially fixed in both the 18- and 17-electron complexes. The radical cation of thetrans-bis(ethene) complex was observed only at 243 K, while at room temperature it isomerized rapidlyto the corresponding cis-isomer. The thermal stability of the three studied radical cations in the cisconfiguration correlates with the relative strength of the W-CO bonds in the positions trans to the olefinligand, which are more affected by the oxidation than the axial W-CO bonds. For the bulky norborneneligands, their trans configuration in the bis(norbornene) complex remains preserved after the oxidationin the whole temperature range studied. The limited thermal stability of the radical cations of the trans-bis(alkene) complexes is ascribed to dissociation of the alkene ligands. The spectroelectrochemical resultsare in very good agreement with data obtained earlier by DFT (B3LYP) calculations.