Borole derivatives. 20. Three-center Fe-H-B bonding in (borole)(cyclopentadienyl)hydridoiron derivatives.
Borole derivatives. 20. Three-center Fe-H-B bonding in (borole)(cyclopentadienyl)hydridoiron derivatives.
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硼罗衍生物。
DOI：
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
U. Zenneck
中科院分区：
文献类型：
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作者：
G. E. Herberich;Tobias Carstensen;D. P. J. Koeffer;N. Klaff;R. Boese;I. Hyla;R. Gleiter;M. Stephan;Helmut Meth;U. Zenneck
3，4-R12C4H2BPh(3a，r1=H；3b，r1=Me)与环戊二烯在红外条件下发生反应。得到氢化物CpFeH(3，4-R12C4H2BPh)(1a，b)。NaH在四氢呋喃中去质子化生成硼铁阴离子[CPFE(3，4-R12C4H2BPh)]-(5a，b)。它们可以在NaH存在下通过烷基碘在2/5-位上烷基化得到2，5-二烷基氢化物：例如CpFeH(2，5-R22C4H2BPh)[1c，R2=Me，1g，R2=CH2：CH(CH2)4；1h，R2=(CH2)2CHCH2]。测定了CpFeH(2，3，4，5-Me4C4BPh)(1d)和(C5H4Me)FeH(2，5-Me2C4H2BPh)(1f)的结构。被低温。X-射线衍射谱表明存在一个具有弱B-H相互作用的Fe-H-B三中心键。在索恩。建立一个流动的马匹。Fe-H-B三中心键合的基态和Fe-H-C-2(C4H4B)三中心键合的异构体。DG=1.4千卡/摩尔。氢化质子和硼环上的2-/5-质子发生快速内摩尔反应。交换。作为一种交换机制，提出了一个氢原子参与的三个氢原子的旋转木马，穿过了硼配体的外向面。用扩展的Hueckel方法分析了CpFeH(C4H4BH)的成键过程，证实了CpFeH(C4H4BH)为Fe-H-B三中心成键。探索性扩展的Hueckel计算。还支持异构体的存在以及拟议的交换机制。循环伏安法证实了17E络合物CPFE(C4H4BPh)(5a)的存在，并通过EPR和顺磁1HNMR谱对其进行了表征。1a与CNBut反应生成环戊烯基硼配合物CPFE(CNBut)(C4H5BPh)，可能通过中间体Fe(CNBut)(C4H4BPh)(C5H6)生成硼烷配合物Fe(CNBut)3(C4H4BPh)和1当量的环戊二烯。给外宾贴标签。结果表明，氢化氢向硼烷和Cp配体的转移是一个内摩尔过程。进程。1C的反应类似。
(Borole)tricarbonyliron complexes Fe(CO)3(3,4-R12C4H2BPh) (3a, R1 = H; 3b, R1 = Me) react with cyclopentadiene under irradn. to give the hydrides CpFeH(3,4-R12C4H2BPh) (1a, b). Deprotonation by NaH in THF produces the borataferrocene anions [CpFe(3,4-R12C4H2BPh)]- (5a, b). These can be alkylated in the 2-/5-position by alkyl iodides in the presence of NaH to give 2,5-dialkyl hydride derivs.: e.g. CpFeH(2,5-R22C4H2BPh) [1c, R2 = Me, 1g, R2 = CH2:CH(CH2)4; 1h, R2 = (CH2)2CHCH2]. The structures of CpFeH(2,3,4,5-Me4C4BPh) (1d) and (C5H4Me)FeH(2,5-Me2C4H2BPh) (1f) as detd. by low-temp. x-ray diffraction show the presence of an Fe-H-B three-center bond with a weak B-H interaction. In soln. 1a establishes a mobile equil. between the ground state with Fe-H-B three-center bonding and the agostic isomer with Fe-H-C-2(C4H4B) three-center bonding with an estd. DG = 1.4 kcal/mol. The hydridic proton and the 2-/5-protons of the borole ring undergo fast intramol. exchange. A merry-go-round of the three H atoms involved with one hydrogen crossing the exo face of the borole ligand is proposed as an exchange mechanism. The bonding of CpFeH(C4H4BH) is analyzed by means of extended Hueckel calcns., which confirm the Fe-H-B three-center bonding. Exploratory extended Hueckel calcns. also support the existence of agostic isomers as well as the proposed exchange mechanism. Cyclic voltammetry revealed the existence of the 17e complex CpFe(C4H4BPh) (5a), which is characterized by its EPR and paramagnetic 1H NMR spectra. 1A reacts with CNBut to give the boracyclopentenyl complex CpFe(CNBut)(C4H5BPh) and, probably via the intermediate Fe(CNBut)(C4H4BPh)(C5H6), the borole complex Fe(CNBut)3(C4H4BPh) and 1 equiv of cyclopentadiene. Labeling expts. show that the shift of the hydride hydrogen to the borole and Cp ligands, resp., is an intramol. process. 1C reacts analogously.