On the Mechanism of Coherent Dihydrogen Tunneling in Transition Metal Trihydrides
On the Mechanism of Coherent Dihydrogen Tunneling in Transition Metal Trihydrides
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过渡金属三氢化物中相干二氢隧穿机理的研究
DOI：
10.1002/anie.199213691
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发表时间：
1992
影响因子：
--
通讯作者：
B. Chaudret
中科院分区：
文献类型：
--
作者：
H. Limbach;G. Scherer;M. Maurer;B. Chaudret
透明配合物非常短（2.491(1) A），是由五个硫醇盐 S 原子的不寻常排列产生的，这些原子占据了三角双锥的顶点，同时也以四面体的方式围绕着两个金属原子（图 1 右）。因此，钴原子占据两个硫四面体的中心，这两个四面体具有共同的面（S3-S4-S5）。三个桥连配体的位置使得异丙基具有桨轮状排列，即它们相对于局部三重轴对称。在晶体中发现了复合阴离子的两个不同方向，它们可以通过简单的旋转叠加。其中一个方向似乎受到大力青睐，入住率约为 64%。两个 CoS 四面体以一种非常典型的方式扭曲。理想的几何形状不仅会导致桥接硫原子处的键角非常小，约为39英寸，而且还会导致金属与金属之间的距离短得不切实际，约为1.52埃。当双锥体沿顶点拉伸直到桥接原子处的键角接近平均值65.4英寸时，观察到的结构是理想的四面体排列的结果。同时Co-Co距离增加到2.491 8，而桥连配体的三个硫原子之间的平均距离减小到3.362 A。因此，平均(p-S)Co-(p-S)角也相当小(93.58")。末端硫醇配体的Co-S键并不完全平行于Co-Co轴。轻微的倾斜(8.1")产生了三种不同的角度。 S-Co-(p-S) 角（平均值为 11 5.3、123.2 和 129.1"）。Co-(p-S) 和 Co-S 键的平均长度分别为 2.307 和 2.210 A（平均 2.283 A），比其他硫醇钴（I1）配合物稍短；这在与双核配合物的比较中尤其明显络合阴离子 [Co,(SC,H,),IZ-，其中每个 Co 原子与两个末端和两个桥接硫醇配体结合，对于顺式，相应值为 2.355 和 2.270 8，对于反式，相应值为 2.363 和 2.213 8 顺式例子 ~ ~ ~ ~ [ CO , ( SC , H , ) , ] ~ ['I 清楚地说明。在具有四面体 CoS、单元和单官能配体的配合物中，从边缘到面共享的变化对 Co-Co 距离具有巨大影响，对于反异构体，这种变化导致相对于 1 增加 0.554 至 3.045(2) A (+ 22.2%)，而对于顺式异构体，则从 0.529 增加至 3.020(3) 8, (+ 21.2)。对于由于特定配体影响而应变的络合物，情况有所不同，例如具有边缘共享 CoS、四面体.lgl 的 [CO,(SCH,C,H,CH,S),]~ 此处双功能配体被结合，使得中心 Co,(p-S) 四元环显着折叠，尽管 Co-Co 距离因此减小到 2.786(1) 8,，但该值仍然是 0.3。 8，比标题化合物 1 中的更长。这些结果表明，硫醇配体的配合物的化学性质比最初假设的要多样化得多。我们认为，具有共同面的四面体配位单元的令人惊讶的形成是由配体的特定电子性质控制的，我们已经有了第一个实验证据，证明具有双四面体 Fe,S, 中心的新型铁硫醇盐的存在。
clear complex is remarkably short (2.491(1) A) and results from the unusual arrangement of the five thiolate S atoms which occupy the vertices of a trigonal bipyramid and simultaneously also surround the two metal atoms in a tetrahedral fashion (Fig. 1 right). The cobalt atoms thus occupy the centers of two sulfur tetrahedra, which have a common face (S3-S4-S5). The three bridging ligands are positioned so that the isopropyl groups have a paddlewheel-like arrangement, that is, they are symmetric with respect to a local threefold axis. Two different orientations of the complex anion are found in the crystal which are superimposable by a simple rotation. One of the orientations appears to be energetically favored with an occupancy of approximately 64%. The two CoS, tetrahedra are distorted in a very characteristic manner. The ideal geometry would not only lead to very small bond angles of about 39" at the bridging sulfur atoms, but also to an unrealistically short metal-metal distance of about 1.52 A. The observed structure results from an ideal tetrahedral arrangement when the bipyramid is stretched along the apices until the bonding angles at the bridging atoms approach the mean value of 65.4". At the same time the Co-Co distance increases to 2.491 8, while the mean distance between the three sulfur atoms of the bridging ligands decreases to 3.362 A. Consequently, the mean (p-S)Co-(p-S) angle is also quite small (93.58"). The Co-S bonds of the terminal thiolato ligands are not completely parallel to the Co-Co axis. The slight tilt (8.1 ") gives rise to three different S-Co-(p-S) angles (mean values 11 5.3, 123.2, and 129.1 "). The mean lengths of the Co-(p-S) and Co-S bonds, 2.307 and 2.210 A, respectively (average 2.283 A), are somewhat shorter than those in other thiolatocobalt(I1) complexes; this is especially evident in the comparison with the dinuclear complex anion [Co,(SC,H,),IZ-, in which each Co atom is bound to two terminal and two bridging thiolato ligands. The corresponding values here are 2.355 and 2.270 8, for the syn, and 2.363 and 2.213 8, for the anti The example of synand ~ ~ ~ ~ [ C O , ( S C , H , ) , ] ~ ['I clearly illustrates that in complexes with tetrahedral CoS, units and monofunctional ligands, the change from edgeto facesharing has a drastic influence on the Co-Co distance. For the anti isomer, this change results in an increase of 0.554 to 3.045(2) A (+ 22.2%) relative to 1, and for the syn isomer of 0.529 to 3.020(3) 8, (+ 21.2 %). The situation is somewhat different for complexes that are strained as a result of specific ligand influences, for example [CO,(SCH,C,H,CH,S),]~ with edge-sharing CoS, tetrahedra.lgl Here the bifunctional ligands are bound so that the central Co,(p-S), four-membered ring is significantly folded. Although the Co-Co distance is thereby reduced to 2.786(1) 8,, this value is still 0.3 8, longer than in the title compound 1. These results show that the chemistry of complexes with thiolato ligands is much more diverse than originally assumed. We suggest that the surprising formation of units with tetrahedral coordination which have common faces is controlled by specific electronic properties of the ligands. We already have the first experimental evidence of the existence of novel iron thiolates with bitetrahedral Fe,S, centers.