六配位[M(NO)](6) σ键合芳基（铁）和-（钌）卟啉中意外的亚硝酰基弯曲

Unexpected nitrosyl-group bending in six-coordinate [M(NO)](6) sigma-bonded aryl(iron) and -(ruthenium) porphyrins.

作者信息

Richter-Addo G B, Wheeler R A, Hixson C A, Chen L, Khan M A, Ellison M K, Schulz C E, Scheidt W R

机构信息

Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Norman, OK 73019, USA.

出版信息

J Am Chem Soc. 2001 Jul 4;123(26):6314-26. doi: 10.1021/ja010276m.

DOI:10.1021/ja010276m

PMID:11427056

Abstract

The six-coordinate nitrosyl sigma-bonded aryl(iron) and -(ruthenium) porphyrin complexes (OEP)Fe(NO)(p-C(6)H(4)F) and (OEP)Ru(NO)(p-C(6)H(4)F) (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 species as well as significant lengthening of trans axial bond distances. In (OEP)Fe(NO)(p-C(6)H(4)F) the Fe-N-O angle is 157.4(2) degrees, the nitrosyl nitrogen atom is tilted off of the normal to the heme plane by 9.2 degrees, Fe-N(NO) = 1.728(2) A, and Fe-C(aryl) = 2.040(3) A. In (OEP)Ru(NO)(p-C(6)H(4)F) the Ru-N-O angle is 154.9(3) degrees, the nitrosyl nitrogen atom is tilted off of the heme normal by 10.8 degrees, Ru-N(NO) = 1.807(3) A, and Ru-C(aryl) = 2.111(3) A. We show that these structural features are intrinsic to the molecules and are imposed by the strongly sigma-donating aryl ligand trans to the nitrosyl. Density functional-based calculations reproduce the structural distortions observed in the parent (OEP)Fe(NO)(p-C(6)H(4)F) and, combined with the results of extended Hückel calculations, show that the observed bending and tilting 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 pi-bonding as measured by infrared and (57)Fe 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 counterparts. The Mössbauer data for (OEP)Fe(NO)(p-C(6)H(4)F) 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.

摘要

已合成并表征了六配位的亚硝酰基σ键合芳基（铁）和 - （钌）卟啉配合物（OEP）Fe（NO）（对 - C₆H₄F）和（OEP）Ru（NO）（对 - C₆H₄F）（OEP = 八乙基卟啉二价阴离子）。单晶X射线结构测定揭示了两种[MNO]₆物种的MNO基团前所未有的弯曲和倾斜以及反式轴向键距的显著延长。在（OEP）Fe（NO）（对 - C₆H₄F）中，Fe - N - O角为157.4（2）°，亚硝酰基氮原子偏离血红素平面法线9.2°，Fe - N（NO） = 1.728（2）Å，Fe - C（芳基） = 2.040（3）Å。在（OEP）Ru（NO）（对 - C₆H₄F）中，Ru - N - O角为154.9（3）°，亚硝酰基氮原子偏离血红素法线10.8°，Ru - N（NO） = 1.807（3）Å，Ru - C（芳基） = 2.111（3）Å。我们表明这些结构特征是分子固有的，并且是由与亚硝酰基反位的强σ供体芳基配体所导致的。基于密度泛函的计算重现了母体（OEP）Fe（NO）（对 - C₆H₄F）中观察到的结构畸变，并且与扩展休克尔计算结果相结合，表明观察到的FeNO基团的弯曲和倾斜确实代表了一种低能量构象。我们已经确定了有利于FeNO基团意外弯曲和倾斜的特定轨道相互作用。芳基配体还通过红外光谱和⁵⁷Fe穆斯堡尔光谱测量影响Fe - NO π键合。铁配合物（1791 cm⁻¹）和钌配合物（1773 cm⁻¹）的固态亚硝酰基伸缩频率与其各自的[MNO]₆对应物相比显著降低。（OEP）Fe（NO）（对 - C₆H₄F）的穆斯堡尔数据在4.2 K时给出四极分裂参数 +0.57 mm/s和同质异能位移0.14 mm/s。我们的研究结果首次表明，在形式上的三价铁亚硝酰基卟啉中弯曲的Fe - N - O键是可能的。