Unexpected nitrosyl-group bending in six-coordinate [M(NO)](6) sigma-bonded aryl(iron) and -(ruthenium) porphyrins.
Unexpected nitrosyl-group bending in six-coordinate [M(NO)](6) sigma-bonded aryl(iron) and -(ruthenium) porphyrins.
复制标题
六配位 [M(NO)](6) σ 键合的芳基（铁）和 -（钌）卟啉中出现意外的亚硝酰基弯曲。
DOI：
10.1021/ja010276m
复制
发表时间：
2001
影响因子：
15
通讯作者：
Scheidt,WR
中科院分区：
文献类型：
--
作者：
Richter-Addo,GB;Wheeler,RA;Hixson,CA;Chen,L;Khan,MA;Ellison,MK;Schulz,CE;Scheidt,WR
合成了六配位亚硝基σ键芳基（铁）-（钌）卟啉配合物（OEP）Fe(NO)（p-C6H4F）和（OEP）Ru(NO)(p-C6H4F) （OEP =八乙基卟啉酸）。单晶x射线结构测定揭示了两个{MNO}6物种的MNO基团的前所未有的弯曲和倾斜以及跨轴键距离的显着延长。在（OEP）Fe(NO)（p-C6H4F）中，Fe−N−O角为157.4(2)°，亚硝基氮原子向血红素平面倾斜9.2°，Fe−N(NO) = 1.728(2) Å， Fe−C（芳基）= 2.040(3)Å。在（OEP）Ru(NO)（p-C6H4F）中，Ru−N−O角为154.9(3)°，亚硝基氮原子偏离血红素正态线10.8°，Ru−N(NO) = 1.807(3) Å， Ru−C（芳基）= 2.111(3)Å。我们发现这些结构特征是分子固有的，并且是由强给σ芳基配体反式到亚硝基所施加的。基于密度函数的计算再现了在母（OEP）Fe(NO)（p-C6H4F）中观察到的结构畸变，并结合扩展h<s:1> ckel计算的结果，表明观察到的FeNO基团的弯曲和倾斜确实代表了低能构象。我们已经确定了有利于FeNO基团意想不到的弯曲和倾斜的特定轨道相互作用。用红外光谱和57fe Mössbauer光谱测量了芳基配体对Fe - NO π键的影响。铁配合物（1791 cm-1）和钌配合物（1773 cm-1）的固态亚硝基拉伸频率与它们各自的{MNO}6相比显著降低。（OEP）Fe(NO)（p-C6H4F）在4.2 K下的四极分裂参数为+0.57 mm/s，同分异构体位移为0.14 mm/s。我们的研究结果首次表明，在形式上的铁亚硝基卟啉中可能存在弯曲的Fe−N−O键。
The six-coordinate nitrosyl σ-bonded aryl(iron) and -(ruthenium) porphyrin complexes (OEP)Fe(NO)(p-C6H4F) and (OEP)Ru(NO)(p-C6H4F) (OEP = octaethylporphyrinato dianion) have been synthesized and characterized. Single-crystal X-ray structure determinations reveal an unprecedented bending and tilting of the MNO group for both {MNO}6species as well as significant lengthening of trans axial bond distances. In (OEP)Fe(NO)(p-C6H4F) the Fe−N−O angle is 157.4(2)°, the nitrosyl nitrogen atom is tilted off of the normal to the heme plane by 9.2°, Fe−N(NO) = 1.728(2) Å, and Fe−C(aryl) = 2.040(3) Å. In (OEP)Ru(NO)(p-C6H4F) the Ru−N−O angle is 154.9(3)°, the nitrosyl nitrogen atom is tilted off of the heme normal by 10.8°, Ru−N(NO) = 1.807(3) Å, and Ru−C(aryl) = 2.111(3) Å. We show that these structural features are intrinsic to the molecules and are imposed by the strongly σ-donating aryl ligand trans to the nitrosyl. Density functional-based calculations reproduce the structural distortions observed in the parent (OEP)Fe(NO)(p-C6H4F) and, combined with the results of extended Hückel calculations, show that the observed bendingandtilting of the FeNO group indeed represent a low-energy conformation. We have identified specific orbital interactions that favor the unexpected bending and tilting of the FeNO group. The aryl ligand also affects the Fe−NO π-bonding as measured by infrared and57Fe Mössbauer spectroscopies. The solid-state nitrosyl stretching frequencies for the iron complex (1791 cm-1) and the ruthenium complex (1773 cm-1) are significantly reduced compared to their respective {MNO}6counterparts. The Mössbauer data for (OEP)Fe(NO)(p-C6H4F) yield the quadrupole splitting parameter +0.57 mm/s and the isomer shift 0.14 mm/s at 4.2 K. The results of our study show, for the first time, that bent Fe−N−O linkages are possible in formally ferric nitrosyl porphyrins.