Bimetallic nickel-lutetium complexes: tuning the properties and catalytic hydrogenation activity of the Ni site by varying the Lu coordination environment
Bimetallic nickel-lutetium complexes: tuning the properties and catalytic hydrogenation activity of the Ni site by varying the Lu coordination environment
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双金属镍镥配合物：通过改变Lu配位环境来调节Ni位点的性能和催化加氢活性
DOI：
10.1039/c8sc04712j
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发表时间：
2019
期刊：
影响因子：
8.4
通讯作者：
Lu, Connie C.
中科院分区：
文献类型：
--
作者：
Ramirez, Bianca L.;Sharma, Prachi;Eisenhart, Reed J.;Gagliardi, Laura;Lu, Connie C.
我们提出了三个heterodynamic配合物包含一个同构的镍中心和镥离子在不同的协调环境。用双齿配体iPr 2 PCH 2NHPh和九齿配体（iPr 2 PCH 2NHAr）3 tacn分别合成了Lu（iPr 2 PCH 2NPh）3（1）和Lu{（iPr 2 PCH 2NAr）3 tacn}（2）。Ni（COD）2（其中COD为1，5-环辛烯）与1反应得到NiLu（iPr 2 PCH 2NPh）3（3），其中Lu配位数（CN）为4，Ni-Lu距离d（Ni-Lu）为2.4644（2）nm。配合物3可以进一步结合THF以形成3-THF，将Lu CN增加到5并且将d（Ni-Lu）增加到2.5989（4）N。另一方面，将Ni（0）引入到2中提供NiLu{（iPr 2 PCH 2NAr）3 tacn}（4），其中Lu配位环境更饱和（CN = 6），并且d（Ni-Lu）在2.9771（5）nm处基本上伸长。三种Ni-Lu络合物的循环伏安法显示Ni（0/I）氧化还原电对中的总体10410 mV偏移，表明Ni电子器件在整个系列中的可调谐性。计算结果表明，Ni 3dz 2（主轨道）和Lu 5dz 2（次轨道）之间存在极化成键作用，Lu 5dz 2所占比例依次为：4（6.0%Lu 5dz 2）< 3-THF（8.5%）< 3（9.3%）.所有三种镍-钌配合物在低温（−30至−80 °C）下结合H2，是苯乙烯氢化的合适催化剂。复合体3以四倍的速度超过4。此外，增加THF当量至3（这将有利于3-THF的积累）降低了速率。我们提出，改变Lu载体的配位范围可以影响活性Ni（0）金属中心的所得性质和催化活性。
We present three heterobimetallic complexes containing an isostructural nickel center and a lutetium ion in varying coordination environments. The bidentate iPr2PCH2NHPh and nonadentate (iPr2PCH2NHAr)3tacn ligands were used to prepare the Lu metalloligands, Lu(iPr2PCH2NPh)3 (1) and Lu{(iPr2PCH2NAr)3tacn} (2), respectively. Reaction of Ni(COD)2 (where COD is 1,5-cyclooctadiene) and 1 afforded NiLu(iPr2PCH2NPh)3 (3), with a Lu coordination number (CN) of 4 and a Ni–Lu distance, d(Ni–Lu), of 2.4644(2) Å. Complex 3 can further bind THF to form 3-THF, increasing both the Lu CN to 5 and d(Ni–Lu) to 2.5989(4) Å. On the other hand, incorporation of Ni(0) into 2 provides NiLu{(iPr2PCH2NAr)3tacn} (4), in which the Lu coordination environment is more saturated (CN = 6), and the d(Ni–Lu) is substantially elongated at 2.9771(5) Å. Cyclic voltammetry of the three Ni–Lu complexes shows an overall ∼410 mV shift in the Ni(0/I) redox couple, suggesting tunability of the Ni electronics across the series. Computational studies reveal polarized bonding interactions between the Ni 3dz2 (major) and the Lu 5dz2 (minor) orbitals, where the percentage of Lu character increases in the order: 4 (6.0% Lu 5dz2) < 3-THF (8.5%) < 3 (9.3%). All three Ni–Lu complexes bind H2 at low temperatures (−30 to −80 °C) and are competent catalysts for styrene hydrogenation. Complex 3 outperforms 4 with a four-fold faster rate. Additionally, adding increasing THF equivalents to 3, which would favor build-up of 3-THF, decreases the rate. We propose that altering the coordination sphere of the Lu support can influence the resulting properties and catalytic activity of the active Ni(0) metal center.