期刊
INORGANIC CHEMISTRY
卷 49, 期 14, 页码 6646-6654出版社
AMER CHEMICAL SOC
DOI: 10.1021/ic100641j
关键词
-
资金
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0001798, DE-AC02-06CH11357]
- U.S. Department of Energy, Office of Nuclear Energy [DE-FC07-061D141781]
- Office of Basic Energy Sciences, U.S. Department of Energy [DE-SC002183]
The compounds Tc2Cl4(PMe3)(4) and Tc2Br4(PMe3)(4) were formed from the reaction between (n-Bu4N)(2)Tc2X8 (X = Cl, Br) and trimethylphosphine. The Tc(II) dinuclear species were characterized by single-crystal XRD, UV-visible spectroscopy, and cyclic voltammetry techniques, and the results are compared to those obtained from density functional theory and multiconfigurational (CASSCF/CASPT2) quantum chemical studies. The compound Tc2Cl4-(PMe3)(4) crystallizes in the monoclinic space group C2/c [a = 17.9995(9) angstrom, b = 9.1821(5) angstrom, c = 17.0090(9) angstrom, beta = 115.4530(10)degrees] and is isostructural to M2Cl4(PMe3)(4) (M = Re, Mo, W) and to Tc2Br4(PMe3)(4). The metal-metal distance (2.1318(2) angstrom) is similar to the one found in Tc2Br4(PMe3)(4) (2.1316(5) angstrom). The calculated molecular structures of the ground states are in excellent agreement with the structures determined experimentally. Calculations of effective bond orders for Tc2X82- and Tc2X4(PMe3)(4) (X = Cl, Br) indicate stronger pi bonds in the Tc-2(4+) core than in Tc-2(6+) core. The electronic spectra were recorded in benzene and show a series of low intensity bands in the range 10 000-26 000 cm(-1). Assignment of the bands as well as computing their excitation energies and intensities were performed at both TD-DFT and CASSCF/CASPT2 levels of theory. Calculations predict that the lowest energy band corresponds to the delta* -> sigma* transition, the difference between calculated and experimental values being 228 cm(-1) for X = Cl and 866 cm(-1) for X = Br. The next bands are attributed to delta* -> pi*, delta -> sigma*, and delta -> pi* transitions. The cyclic voltammograms exhibit two reversible waves and indicate that Tc2Br4(PMe3)(4) exhibits more positive oxidation potentials than Tc2Cl4(PMe3)(4). This phenomenon is discussed and ascribed to stronger metal (d) to halide (d) back bonding in the bromo complex. Further analysis indicates that Tc(II) dinuclear species containing pi-acidic phosphines are more difficult to oxidize, and a correlation between oxidation potential and phosphine acidity was established.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据