Molecular and Electronic Structure of Re2Br4(PMe3)4

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• 作者：Erik V. Johnstone ; Frederic Poineau ; Tanya K. Todorova ; Paul M. Forster ; Lasse K. Sørensen ; Ignacio Fdez. Galván ; Roland Lindh ; Kenneth R. Czerwinski ; Alfred P. Sattelberger
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：July 18, 2016
• 年：2016
• 卷：55
• 期：14
• 页码：7111-7116
• 全文大小：336K
• 年卷期：0
• ISSN：1520-510X

文摘

The dinuclear rhenium(II) complex Re₂Br₄(PMe₃)₄ was prepared from the reduction of [Re₂Br₈]^2– with (n-Bu₄N)BH₄ in the presence of PMe₃ in propanol. The complex was characterized by single-crystal X-ray diffraction (SCXRD) and UV–visible spectroscopy. It crystallizes in the monoclinic C2/c space group and is isostructural with its molybdenum and technetium analogues. The Re–Re distance (2.2521(3) Å) is slightly longer than the one in Re₂Cl₄(PMe₃)₄ (2.247(1) Å). The molecular and electronic structure of Re₂X₄(PMe₃)₄ (X = Cl, Br) were studied by multiconfigurational quantum chemical methods. The computed ground-state geometry is in excellent agreement with the experimental structure determined by SCXRD. The calculated total bond order (2.75) is consistent with the presence of an electron-rich triple bond and is similar to the one found for Re₂Cl₄(PMe₃)₄. The electronic absorption spectrum of Re₂Br₄(PMe₃)₄ was recorded in benzene and shows a series of low-intensity bands in the range 10 000–26 000 cm^–1. The absorption bands were assigned based on calculations of the excitation energies with the multireference wave functions followed by second-order perturbation theory using the CASSCF/CASPT2 method. Calculations predict that the lowest energy band corresponds to the δ* → σ* transition, while the next higher energy bands were attributed to the δ* → π*, δ → σ*, and δ → π* transitions.