Structural characterizations of salts of HCr(CO)5- and (μ-H)2BH2Cr(CO)4- and studies of their interconversions
Structural characterizations of salts of HCr(CO)5- and (μ-H)2BH2Cr(CO)4- and studies of their interconversions
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HCr(CO)5- 和 (μ-H)2BH2Cr(CO)4- 盐的结构表征及其相互转化的研究
DOI：
10.1021/ja00389a013
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发表时间：
1982
影响因子：
15
通讯作者：
S. Slater
中科院分区：
文献类型：
--
作者：
M. Darensbourg;R. Bau;Melodye W. Marks;R. Burch;J. Deaton;S. Slater
在0 ℃下，BH 3与HCr（CO）5”在THF中反应以提取氢化物，推测产生配位不饱和的Cr（CO）5，其立即与剩余的HCr（CO）5”聚集以产生非常稳定的（MH）[Cr 2（CO）10“。在室温下，得到两个桥接氢化物产物。除了双核桥接氢化物之外，第二产物（MH）2BH 2Cr（CO）4“是在Cr-H-BH 3加合物形成之前或之后由CO损失产生的。硼氢化物络合物在加入CO时可以再转化为HCr（CO）5-;然而，在该过程中还形成（MH）[Cr 2（CO）10]-。两个标题阴离子的盐，其特征在于通过溶液光谱探针以及X-射线结构分析。[Ph_4P][HCr（CO）_5]晶体属四面体空间群P_4/n，a= 13.234（2）A，B= 13.234（2）A，c= 7.472（2）A，Z= 2.对于I> 3的1796次反射，R（F）= 3.9%（7）。[PPN][（MH）2BH 2Cr（CO）4]的深红色晶体属于三斜晶系空间群PT，a= 11.708（3）A，B= 14.572（6）A，c= 11.454（3）A，a= 101.98（3），λ = 91.69（2），π = 77.34（3），Z= 2。对于2880次反射，R（F）= 6.6%，其中f> 3（）。最值得注意的是，HCr（CO）5-显示出晶体学上相同的赤道CO基团向氢化物配体（zfCO（x-Cr-fCO），*，= 95.4（1））弯曲，正如所有结构已知的单核双羰基络合物所显示的那样。对v（CO）红外光谱的分析表明，这种假八面体结构在溶液中持续存在。氢化物配体对Cr-C键长的影响很小，Cr-Ctrans= 1.852（4）A，Cr-Ccis= 1.865（3）A。氢化物配体位于距Cr 1.66（5）A处。相反，（qH）_2BH_2Cr（CO）_4 ′的Cr-C键表现出相当大的不对称性，Cr-C_（qf反式）= 1.81（1）和1.82（1）A，Cr-C_（cis）= 1.87（1）和1.85（1）A。此外，轴向CO基团弯曲远离[0 i-H）2BCr]平面单元，Z（CO）ax-Cr-（CO）ax= 175.6（4），而赤道CO基团扩展到由（μ-）2双齿配体的小需求所提供的空间中，Z（CO）eq-Cr-（CO）eq= 94.8（4）。碳-13核磁共振光谱显示（μ-）2 20（0）4“的CO基团在+30 ℃下是立体化学刚性的，而核磁共振光谱显示桥氢和末端氢的快速交换，即使在-80 ℃下也是如此。
At 0 C, BH3 reacted with HCr (CO) 5" in THF to abstract hydride, presumablyproducing coordinatively unsaturated Cr (CO) 5, which immediately aggregated with remaining HCr (CO) 5" to yield the very stable (MH)[Cr2 (CO) 10]'. At room temperature two bridging hydride products were obtained. In addition to the binuclear bridging hydride, a second product,(MH) 2BH2Cr (CO) 4 “, resulted from CO loss either prior to or following Cr-H—BH3 adduct formation. The borohydride complex could be reconverted to HCr (CO) 5" on addition of CO; however,(MH)[Cr2 (CO) 10]“was also formed in the process. Salts of both title anions were characterized by solution spectroscopic probes as well as X-ray structural analysis. Crystals of [Ph4P][HCr (CO) 5] were found to belong to the tetragonal space group P4/n, with a= 13.234 (2) A, b= 13.234 (2) A, c= 7.472 (2) A, and Z= 2. R (F)= 3.9% for 1796 reflections with I> 3 (7). Deep red crystals of [PPN][(MH) 2BH2Cr (CO) 4] belong to the triclinic space group PT, with a= 11.708 (3) A, b= 14.572 (6) A, c= 11.454 (3) A, a= 101.98 (3), ß= 91.69 (2), 7= 77.34 (3), and Z= 2. R (F)= 6.6% for 2880 reflections with/> 3 (). Most notably, HCr (CO) 5-showed bending of the crystallographically identical equatorial CO groups toward the hydride ligand (zfCOljx-Cr-fCO),*,= 95.4 (1)), as has been exhibited by all mononuclear hydridocarbonyl complexeswhose structures are known. Analysis of the v (CO) infrared spectrum indicated that this pseudooctahedralstructure persisted in solution. The hydride ligand induced only a very small trans effect on the Cr-C bond length with Cr-Ctrans= 1.852 (4) A and Cr-Ccis= 1.865 (3) A. The hydride ligand was located 1.66 (5) A from Cr. In contrast the Cr-C bonds of (qH) 2BH2Cr (CO) 4 ‘showed considerable asymmetry with Cr-Cjqftrans to)= 1.81 (1) and 1.82 (1) A and Cr-Cax (cis to)= 1.87 (1) and 1.85 (1) A. In addition, the axial CO groups bend away from the [0i-H) 2BCr] planar unit, Z (CO) ax-Cr-(CO) ax= 175.6 (4), whereas the equatorial CO groups expand into the space made available by the small requirement of the (µ-) 2 bidentate ligand, Z (CO) eq-Cr-(CO) eq= 94.8 (4). Carbon-13 NMR spectroscopy showed the CO groups of (µ-) 2 20 (0) 4 “to be stereochemically rigid at+ 30 C whereas NMR spectroscopy showed rapid interchange of bridging and terminal hydrogens, even at-80 C.