Orto Peter J, Nichol Gary S, Okumura Noriko, Evans Dennis H, Arratia-Pérez Ramiro, Ramirez-Tagle Rodrigo, Wang Ruiyao, Zheng Zhiping
Department of Chemistry, The University of Arizona, Tucson, Arizona 85721, USA.
Dalton Trans. 2008 Aug 28(32):4247-53. doi: 10.1039/b806973e. Epub 2008 Jul 15.
The reactions of the previously reported cluster complexes [Re(6)(mu(3)-Se)(8)(PEt(3))(5)I]I, trans-[Re(6)(mu(3)-Se)(8)(PEt(3))(4)I(2)], and cis-[Re(6)(mu(3)-Se)(8)(PEt(3))(4)I(2)] with the Re(6)(mu(3)-Se)(8) core with CO in the presence of AgSbF(6) afforded the corresponding cluster carbonyls [Re(6)(mu(3)-Se)(8)(PEt(3))(5)(CO)]SbF(6) (), trans-[Re(6)(mu(3)-Se)(8)(PEt(3))(4)(CO)(2)]SbF(6) (), and cis-[Re(6)(mu(3)-Se)(8)(PEt(3))(4)(CO)(2)]SbF(6) (). Infrared spectroscopy indicated weakening of the bond in CO, suggesting the existence of backbonding between the cluster core and the CO ligand(s). Electrochemical studies focusing on the reversible, one-electron oxidation of the cluster core revealed a large increase in the oxidation potential upon going from the acetonitrile derivatives to their carbonyl analogs, consistent with the depleted electron density of the cluster core upon CO ligation. Disparities between the IR spectra and oxidation potential between and indicate that electronic differences exist between sites trans and cis to the location of a ligand of interest. The active role played by the Se atoms in influencing the cluster-to-CO bonding interactions is suggested through this result and density functional (DF) computational analysis. The computations indicate that molecular orbitals near the HOMO account for backbonding interactions with a high percentage of participation of Se orbitals.
先前报道的具有Re(6)(μ(3)-Se)(8)核心的簇合物[Re(6)(μ(3)-Se)(8)(PEt(3))(5)I]I、反式-[Re(6)(μ(3)-Se)(8)(PEt(3))(4)I(2)]和顺式-[Re(6)(μ(3)-Se)(8)(PEt(3))(4)I(2)]在AgSbF(6)存在下与CO反应，得到了相应的簇羰基化合物[Re(6)(μ(3)-Se)(8)(PEt(3))(5)(CO)]SbF(6) ()、反式-[Re(6)(μ(3)-Se)(8)(PEt(3))(4)(CO)(2)]SbF(6) ()和顺式-[Re(6)(μ(3)-Se)(8)(PEt(3))(4)(CO)(2)]SbF(6) ()。红外光谱表明CO中化学键减弱，这表明簇核心与CO配体之间存在反馈键合。聚焦于簇核心可逆单电子氧化的电化学研究表明，从乙腈衍生物转变为其羰基类似物时，氧化电位大幅增加，这与CO配位后簇核心电子密度降低一致。和之间的红外光谱和氧化电位差异表明，在所关注配体位置的反式和顺式位点之间存在电子差异。通过该结果和密度泛函(DF)计算分析表明，Se原子在影响簇与CO键合相互作用中发挥了积极作用。计算表明，靠近最高占据分子轨道(HOMO)的分子轨道对反馈键合相互作用有贡献，且Se轨道参与比例较高。
